From neurons to neighborhoods

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From Neurons to Neighborhoods: The

Science of Early Childhood Development

(2000)

608 pages | 6 x 9 | HARDBACK

ISBN 978-0-309-06988-5 | DOI 10.17226/9824

Jack P. Shonkoff and Deborah A. Phillips, Editors; Committee on Integrating the

Science of Early Childhood Development; Board on Children, Youth, and Families;

Institute of Medicine; National Research Council

National Research Council. 2000. From Neurons to Neighborhoods: The Science of

Early Childhood Development. Washington, DC: The National Academies Press.

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From Neurons to Neighborhoods: The Science of Early Childhood Development

http://nap.nationalacademies.org/9824

From Neurons to Neighborhoods: The Science of Early Childhood Development

Committee on Integrating the Science of

Early Childhood Development

Jack P. Shonkoff and

Deborah A. Phillips, Editors

Board on Children, Youth, and Families

National Research Council

and

Institute of Medicine

NATIONAL ACADEMY PRESS

Washington, D.C.

From Neurons

to Neighborhoods

The Science of

Early Childhood

Development

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From Neurons to Neighborhoods: The Science of Early Childhood Development

NATIONAL ACADEMY PRESS 2101 Constitution Avenue, N.W. Washington, D.C. 20418

NOTICE: The project that is the subject of this report was approved by the

Governing Board of the National Research Council, whose members are drawn from the

councils of the National Academy of Sciences, the National Academy of Engineering,

and the Institute of Medicine. The members of the committee responsible for the report

were chosen for their special competences and with regard for appropriate balance.

The study was supported by funds provided by the National Institute of Child Health

and Human Development, the National Institute of Mental Health, the Office of Mater-

nal and Child Health Bureau of the Health Resources and Services Administration, the

Substance Abuse and Mental Health Services Administration, the Centers for Disease

Control and Prevention, the National Institute of Nursing Research, the U.S. Department

of Health and Human Services’ Office of the Assistant Secretary for Planning and Evalu-

ation, the Administration on Children, Youth, and Families, the Administration for

Children and Families, the Office of Special Education Programs in the U.S. Department

of Education, The Commonwealth Fund, the Ewing Marion Kauffman Foundation, the

Heinz Endowments, the Irving B. Harris Foundation, and National Academies funds.

Any opinions, findings, conclusions, or recommendations expressed in this publication

are those of the author(s) and do not necessarily reflect the view of the organizations or

agencies that provided support for this project.

Library of Congress Cataloging-in-Publication Data

From neurons to neighborhoods : the science of early child development / Jack P.

Shonkoff and Deborah A. Phillips, editors.

p. cm.

Includes bibliographical references and index.

ISBN 0-309-06988-2 (hardover : alk. paper)

1. Child development—United States. 2. Preschool children—United States. 3.

Preschool children—Services for—United States. 4. Nature and nurture—United States.

5. Early childhood education—United States. I. Shonkoff, Jack P. II. Phillips, Deborah.

HQ767.9.F76 2000

301.231—dc21 00-010760

Additional copies of this report are available from National Academy Press, 2101 Con-

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or (202) 334-3313 (in the Washington metropolitan area). This report is also available

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Printed in the United States of America

Suggested citation: National Research Council and Institute of Medicine (2000) From

Neurons to Neighborhoods: The Science of Early Childhood Development. Committee

on Integrating the Science of Early Childhood Development. Jack P. Shonkoff and

Deborah A. Phillips, eds. Board on Children, Youth, and Families, Commission on

Behavioral and Social Sciences and Education. Washington, D.C.: National Academy

Press.

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From Neurons to Neighborhoods: The Science of Early Childhood Development

The National Academy of Sciences is a private, nonprofit, self-perpetuating society

of distinguished scholars engaged in scientific and engineering research, dedicated

to the furtherance of science and technology and to their use for the general welfare.

Upon the authority of the charter granted to it by the Congress in 1863, the Acad-

emy has a mandate that requires it to advise the federal government on scientific and

technical matters. Dr. Bruce M. Alberts is president of the National Academy of

Sciences.

The National Academy of Engineering was established in 1964, under the charter of

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The National Research Council was organized by the National Academy of Sciences

in 1916 to associate

from evaluations of early

childhood interventions, the committee recommends substantially increased

attention to program implementation as an integral component of all early

childhood evaluation research, the adoption of higher standards for the use

of rigorous and appropriate evaluation study designs, the inclusion of early

childhood outcomes in evaluations of broad-based community and eco-

nomic interventions, and the convening of regular forums at the National

Institutes of Health to synthesize evaluation research evidence across pro-

grams and strategies that share similar developmental aims.

CONCLUDING THOUGHTS

As this report moved to completion, it became increasingly clear to the

members of the committee that the science of early childhood development

has often been viewed through highly personalized and sharply politicized

lenses. In many respects, this is an area in which personal experience allows

everyone to claim some level of expertise. Moreover, as a public issue,

questions about the care and protection of children confront many of the

basic values that have defined our country from its founding—personal

responsibility, individual self-reliance, and restrained government involve-

ment in people’s lives. In a highly pluralistic society that is experiencing

dramatic economic and social change, however, the development of chil-

dren must be viewed as a matter of intense concern for both their parents

and for the nation as a whole.

In this context, and based on the evidence gleaned from a rich and

rapidly growing knowledge base, we feel an urgent need to call for a new

national dialogue focused on rethinking the meaning of both shared re-

sponsibility for children and strategic investment in their future. The time

has come to stop blaming parents, communities, business, and government,

and to shape a shared agenda to ensure both a rewarding childhood and a

promising future for all children.

The charge to this committee was to blend the knowledge and insights

of a broad range of disciplines to generate an integrated science of early

childhood development. The charge to society is to blend the skepticism of

a scientist, the passion of an advocate, the pragmatism of a policy maker,

the creativity of a practitioner, and the devotion of a parent—and to use

existing knowledge to ensure both a decent quality of life for all of our

children and a productive future for the nation.

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From Neurons to Neighborhoods: The Science of Early Childhood Development

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From Neurons to Neighborhoods: The Science of Early Childhood Development

Setting the StageI

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From Neurons to Neighborhoods: The Science of Early Childhood Development

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From Neurons to Neighborhoods: The Science of Early Childhood Development

Introduction

arents have always been captivated by the rapid

growth and development that characterize the earli-

est years of their children’s lives. The first responsive smile, the first wobbly

step, the first recognizable word—each is a significant personal achieve-

ment and an occasion for family celebration. As the months turn to years,

unsteady toddling across the living room turns into powerful sprinting

across the soccer field, spontaneous smiles evolve into rich friendships, and

single words become the building blocks of simple storytelling and, eventu-

ally, complex conversations. As the infant becomes a toddler and then a

preschooler and finally arrives at his or her first day in kindergarten, par-

ents exclaim, “I can’t believe how quickly my baby has grown up!”—and

they frequently wonder about whether they have done a good enough job.

Scientists also have had a long-standing fascination with the process of

early childhood development. The systematic study of infant behavior can

be traced back to the early to mid-19th century, when researchers in both

embryology and evolution raised fundamental questions about the origins

and course of human development across the life span (Cairns, 1998;

Kessen, 1965; Maccoby, 1980). By the 1920s, practice-based investigators

in the professions of pediatrics, education, and social work were increasing

their interaction with psychologists in the world of child study, which led to

the establishment of a vibrant, multidisciplinary, scientific discipline that

has continued to grow as a blend of theory, empirical investigation, and

insights derived from professional experience (Richmond, 1967).

One of the most abiding issues explored by developmental scientists,

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From Neurons to Neighborhoods: The Science of Early Childhood Development

20 FROM NEURONS TO NEIGHBORHOODS

and the subject of this report, concerns how biological endowment and

early experience combine to affect later developmental outcomes. Are the

seeds of extraordinary talent present at birth, or are they planted in early

childhood? When do early delays in development signal serious problems

later in life? Does early intelligence predict lifelong achievement? Do child-

hood bullies turn into adult criminals? Do early advantages, such as a

sunny disposition and skilled parents, inoculate a child from subsequent

adversity? Do early harms, such as repeated exposure to family violence,

impose irrevocable constraints on subsequent outcomes?

Interest in these questions is not new, but there have been significant

advances in the understanding of the kinds of changes that occur, and the

way those changes are grounded in both “nature” and “nurture.” Over the

past three decades, the rate of generation of new knowledge about early

childhood development has been staggering. It has led to a number of

advances in both concepts and methods—and it promises to increase even

further in the near future. This scientific explosion has been fueled by

multiple contributions, ranging from theoretical and conceptual advances

to dramatic leaps in both the measurement technology and the computer-

based analytic capacity available to the behavioral and biological sciences.

We are, for example, on the threshold of a revolution in molecular biology

grounded in the decoding of the human genome. The prospect of increasing

collaboration among neurobiologists, geneticists, and social scientists offers

the exciting promise of still greater breakthroughs in understanding the

complex interplay between nature and nurture as they jointly influence the

process of human development during early childhood.

Most recently, increasing interest in the developmental significance of

early life experiences has been fueled by extensive media coverage of re-

search on the developing brain. From governors and state legislators to

business leaders and entertainers, virtually everyone is talking about the

importance of the early childhood period, particularly the first three years

of life. This growing excitement has fueled a proliferation of media cam-

paigns and policy activities focused on infants and toddlers, as well as a

host of entrepreneurial efforts to capitalize on the demand for materials and

experiences to enhance early competence. At the same time, skeptics have

stepped forward to question this intense interest in very young children, to

point out the limits of contemporary neuroscience, and to underscore the

evidence of continuing brain development far beyond the infant-toddler

period (Bruer, 1999; Kagan, 1998a).

To update what science now tells us about these important issues, the

Board on Children, Youth, and Families of the National Research Council

and the Institute of Medicine established the Committee on

Integrating the

Science of Early Childhood Development. The charge to the committee was

to review what is now known about the nature of early development and

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From Neurons to Neighborhoods: The Science of Early Childhood Development

INTRODUCTION 21

the role of early experiences, to disentangle established knowledge from

erroneous popular beliefs or misunderstandings, and to discuss the implica-

tions of this knowledge base for early childhood policy, practice, profes-

sional development, and research. The goal, then, is not purely one of

summarizing what’s new or what’s fascinating, but rather one of connect-

ing developmental science to its implications for action and continued in-

quiry.

This is a familiar task for developmental scientists, albeit one that is

fraught with difficulties (National Research Council, 1978, 1982; Shonkoff,

2000). Indeed, one of the most distinctive features of the science of early

childhood development is the extent to which it evolves under the anxious

and eager eyes of millions of parents, policy makers, and professional ser-

vice providers who seek authoritative guidance as they address the chal-

lenges of promoting the health and well-being of young children.

Within the framework of its charge, the committee confronted the

following kinds of questions. What are the most important developmental

achievements that occur from the prenatal period up to school entry? Are

there truly “windows of opportunity” in the early years when critical expe-

riences are required for healthy development? When does early adversity

seem to have lasting effects? Which aspects of development are relatively

robust, and which are more sensitive to differences in the environments in

which young children grow up? What aspects of these environments have

the most significant influence on early development? What does it take to

alter the course of development for the better, and what can we realistically

expect from such efforts? How do the answers to these questions vary for

children with different strengths and weaknesses, and who are growing up

in different circ*mstances? The answers to these questions define the na-

ture of early development and the responsibilities of adults. Although the

committee was most familiar with, and thus most sensitive to, the context

in the United States that is now shaping discussion of these issues, it is our

firm hope that this review of the scientific evidence will be seen as pertinent

to children around the world.

The body of research that addresses these questions is extensive, multi-

disciplinary, and more complex than current discourse would lead one to

believe. It covers the period from before birth until the first day of kinder-

garten. It includes efforts to understand how early experience affects all

aspects of development—from the neural circuitry of the maturing brain, to

the expanding network of a child’s social relationships, and to the cultural

values of the society in which parents raise children. It includes efforts to

understand the typical trajectories of early childhood, as well as the atypical

developmental pathways that characterize the adaptations of children with

disabilities. As the knowledge generated by these multiple perspectives has

evolved, a number of core concepts have come to frame our understanding

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From Neurons to Neighborhoods: The Science of Early Childhood Development

22 FROM NEURONS TO NEIGHBORHOODS

of the nature of early human development. They are summarized here and

reemerge repeatedly throughout the report.

CORE CONCEPTS

Defining the boundaries of science in early childhood development is

not an easy task. However, this task can be facilitated for policy makers,

practitioners, and parents by differentiating among established knowledge,

reasonable hypotheses, and unwarranted assertions (Shonkoff, 2000). Es-

tablished knowledge is determined by strict rules of evidence and rigorous

peer review. It evolves continually over time. Reasonable hypotheses are

educated guesses that are derived from, but extend beyond the boundaries

of, established knowledge. Although they may be confirmed or disproved

by subsequent investigation, they make up a large proportion of the knowl-

edge base that guides responsible policy, service delivery, and parenting

practices at any given point in time. Unwarranted assertions distort or

misrepresent current knowledge, undermine its credibility, and have the

greatest potential to be harmful when they are advanced by those who are

viewed as reputable scientists. They are often made to advance commercial

goals or an ideological agenda. Ultimately, informed early childhood policy

making, effective service delivery, and successful parenting are all depen-

dent on mastery of the existing knowledge base, sound judgment based on

reasonable hypotheses, the avoidance of irresponsible practices, and con-

tinuous reassessment over time.

Understanding of child development is based on multiple sources of

knowledge that include theoretical models, empirical research, program

evaluation, and professional experience. The role of theory is to provide a

framework for organizing what is known and for guiding further investiga-

tion. The role of empirical research and program evaluation is to ask im-

portant questions (e.g., How do children learn number concepts?) and to

test specific hypotheses (e.g., High-quality child care results in language

gains for toddlers from high-risk homes), using a variety of quantitative and

qualitative methods. The role of professional experience is to tap the wis-

dom and judgment of people who work with children in a variety of service

settings. Taken together, these diverse sources of knowledge advance un-

derstanding of the process of child development and enhance the capacity

to promote competence, prevent disorders, and correct maladaptive pat-

terns.

A set of core concepts frames our understanding of the nature of hu-

man development during the earliest years of life and lays a foundation for

addressing the following questions:

• Is early development highly programmed, so that certain events must

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From Neurons to Neighborhoods: The Science of Early Childhood Development

INTRODUCTION 23

happen at predetermined times, or is it more loosely open to envi-

ronmental influences and primed to seize those that matter most

whenever they occur?

• Do infants follow a smooth and predictable path toward the pre-

school years (and beyond) or is early growth and development char-

acterized by bumps, detours, and unanticipated turns?

• Are infants initially incompetent, passive creatures or individuals

who are born with an active capability to learn from the surround-

ing world?

• Are young children highly vulnerable, highly resilient, or both?

The discussion provided in this section reflects the prevailing views of

researchers, theorists, and clinicians who study young children. This multi-

dimensional knowledge base has grown exponentially over the past 25

years, fueled by an explosion of scholarly work across a wide variety of

disciplines. Its richness lies in the extent to which diverse perspectives have

converged on a set of core concepts. Its limitations rest on the extent to

which the science is based largely on studies of typical development in

white, middle-class samples and developmental vulnerability in samples

that do not disentangle race, ethnicity, or socioeconomic status.

Focusing on the underlying principles that guide the developmental

process, this report highlights ten guiding principles or core concepts.

1. Human development is shaped by a dynamic and continuous inter-

action between biology and experience. Early pioneers in the field of child

study approached the complexity of human development by devising simple

models and testing them. Some, such as Arnold Gesell (1925, 1929), be-

lieved that the emergence of skills is driven primarily by genes. Others, such

as John B. Watson (1928), believed that all behaviors are determined by the

environment. These early models reflected a mechanistic conceptualization

of development that was derived from the physical sciences. Over time, it

became increasingly clear that humans do not behave like machines (neither

the prewired nor the programmable type), and children began to be viewed

through the lens of modern biology, rather than that of classical physics or

chemistry. Consequently, human development is now described in interac-

tive terms (i.e., “dynamic”), reflecting the essential characteristic of a living

organism.

Virtually all contemporary researchers agree that the development of

children is a highly complex process that is influenced by the interplay of

nature and nurture. The influence of nurture consists of the multiple nested

contexts in which children are reared, which include their home, extended

family, child care settings, community, and society, each of which is embed-

ded in the values, beliefs, and practices of a given culture. The influence of

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From Neurons to Neighborhoods: The Science of Early Childhood Development

24 FROM NEURONS TO NEIGHBORHOODS

nature is deeply affected by these environments and, in turn, shapes how

children respond to their experiences.

In simple terms, children affect their environments at the same time

that their environments are affecting them. Moreover, no two children

share the same environment, and no environment is experienced in exactly

the same way by two different children. Two youngsters living in the same

home influence each other and are affected by the other members of the

family in unique ways. If one child is active and aggressive and the other is

passive and subdued, each will elicit different responses from the parents—

and each will be influenced differently by the behavior of the other.

These concepts reflect what Sameroff and Chandler (1975) character-

ized as the transactional nature of the developmental process and what

Bronfenbrenner (1979) described as the ecology of human development

(also see Horowitz, 1999). This transactional-ecological model of develop-

ment provides a useful framework that moves far beyond the misleading

and tired old nature-nurture debate. It helps people think in more sophisti-

cated ways about the complex determinants of successful adaptation and

health as well as those of maladaptation and disorder. It offers insights into

how the same behavioral disposition may be adaptive in one context and

not in another. It also fits well with what scientists are learning about the

dynamic nature of the development of the brain.

Children vary in their behavioral style. Some are high-strung and some

are laid-back; some are agile and some are clumsy. Children are raised in a

wide variety of social circ*mstances and cultural contexts. Some condi-

tions are secure and others are unstable; some encourage competition and

others promote cooperation. Behaviors that are highly adaptive in one

society (e.g., competitiveness among preschoolers in the United States) may

not be so in another (e.g., individual assertiveness among preschoolers in

Japan). Different childrearing environments promote distinctive patterns of

skill development in some children and not in others (e.g., some may rein-

force active, physical performance while others encourage quiet, artistic

expression).

At every level of analysis, from neurons to neighborhoods, genetic and

environmental effects operate in both directions (Gottlieb, 1992). On one

hand, the gene-environment interactions of the earliest years set an impor-

tant initial course for all of the adaptive variations that follow. On the other

hand, this early trajectory is by no means chiseled in stone. The consider-

able degree of developmental plasticity that characterizes an immature or-

ganism is embodied in the capacity of its cells to adapt in very specific ways,

in both the short and the long run, to changing demands. Neurons grow

new axons, sprout new dendrites, form new synapses, and modify the

strength of some established connections while eliminating others selec-

tively over time. The impacts of varied experiences are also reflected in

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INTRODUCTION 25

observed differences in the brain’s blood supply, its cellular (glial) support

systems, its intercellular insulation (myelin), the neurochemicals that it pro-

duces, and the specific receptors that recognize each individual substance.

These concepts are taken up in more detail in Chapters 2 and 8.

2. Culture influences every aspect of human development and is re-

flected in childrearing beliefs and practices designed to promote healthy

adaptation. The influence of culture on the rearing of children is fundamen-

tal and encompasses values, aspirations, expectations, and practices. Un-

derstanding this realm of influence is central to efforts to understand the

nature of early experience, what shapes it, and how young children and the

culture they share jointly influence each other over the course of develop-

ment. The effects of culture on child development are pervasive. It pre-

scribes how and when babies are fed, as well as where and with whom they

sleep. It affects the customary response to an infant’s crying and a toddler’s

temper tantrums. It sets the rules for discipline and expectations for devel-

opmental attainments. It affects what parents worry about and when they

begin to become concerned. It influences how illness is treated and disabil-

ity is perceived. It approves certain arrangements for child care and disap-

proves others. In short, culture provides a virtual how-to manual for rear-

ing children and establishes role expectations for mothers, fathers,

grandparents, older siblings, extended family members, and friends.

Given the magnitude of its influence on the daily experiences of chil-

dren, the relative disregard for cultural influences in traditional child devel-

opment research is striking. The literature on typical development is based

overwhelmingly on studies of middle-class children of European-American

ancestry, often involving samples drawn from university communities. In

contrast, much of the research on children of color has focused on the

impacts of poverty, drawing its samples from hom*ogeneous communities in

high-risk urban environments. Moreover, relatively little is known about

the impacts of racism and other forms of systematic discrimination on early

childhood development, independent of the adverse effects of low maternal

education and socioeconomic status. Consequently, knowledge of the full

range of environmental influences on young children and their relation to

typical variations during early childhood is highly skewed and incomplete.

Similarly, the ability to disentangle the confounding impacts of economic

hardship and minority group status is severely compromised (García Coll

and Magnuson, 2000).

The influence of cultural context on early childhood development is

widely acknowledged. The empirical literature in this area, however, is

underdeveloped. This weakness in the knowledge base is particularly prob-

lematic in view of the increasing racial and ethnic diversity of the popula-

tion of the United States. In short, the basic concept is compelling, the

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26 FROM NEURONS TO NEIGHBORHOODS

database is thin, and the imperative for

extensive research is clear. These

issues are taken up in more detail in Chapter 3.

3. The growth of self-regulation is a cornerstone of early childhood

development that cuts across all domains of behavior. Regulation is a

fundamental property of all living organisms. It includes physiological and

behavioral regulations that sustain life (e.g., maintenance of body tempera-

ture and conversion of food into energy), as well as those that influence

complex behaviors (e.g., the capacity to pay attention, express feelings, and

control impulses). Regulatory processes modulate a wide variety of func-

tions to keep them within adaptive ranges. The simultaneous operation of

these multiple systems at different levels of organization is an essential

feature of human development, as we discuss at length in Chapter 5.

A broad range of everyday experiences in early childhood are subject to

regulation. In addition, for some children, atypical stresses can overwhelm

their baseline regulatory capacities. Experience with manageable challenges

(e.g., briefly having to wait to be fed or soothed) promotes healthy regula-

tory abilities. Repeated exposure to stresses that are overwhelming (e.g.,

severe malnutrition, chronic abuse) may result in significant maladaptation

or disorder. Individual differences in regulatory capacities are rooted in

both biological endowment and life experience. For example, the underly-

ing neurobiology of irritability and poor attention may be affected by neu-

rotransmitters in the central nervous system that are determined by either

genetics or a chaotic environment. More commonly, regulatory disposi-

tions involve the interplay between both endowment and experience.

As children mature, their capacity to exert their own autonomous con-

trol over key regulatory functions is essential. Advances in motor skills

make it possible for preschoolers to feed themselves when they are hungry

and put on a sweater when they are cold. Cognitive and emotional matura-

tion signals a greater ability to delay gratification, to sit still to read a book,

and to cope with the stresses of separation or loss. Thus, development may

be viewed as an increasing capacity for self-regulation, not so much in the

specifics of individual behaviors but in the child’s ability to function more

independently in personal and social contexts (Bronson, 2000; Kopp, 2000;

Sameroff, 1989; Sroufe and Waters, 1977).

The behaviors children use to regulate themselves and their environ-

ments change in meaning as they get older. What is considered typical and

adaptive at one age may not necessarily be viewed in a comparable fashion

at another age. Crying, for example, is an early regulatory behavior that in

infancy sends important signals to caregivers, yet it may become a sign of

social immaturity if it is used repeatedly to express frustration in middle

childhood. Adaptive behaviors also can have costs, such as the hyper-

vigilance needed to survive in a physically dangerous environment. Finally,

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From Neurons to Neighborhoods: The Science of Early Childhood Development

INTRODUCTION 27

the socialization process and meaning of some regulatory behaviors, such

as physical aggression and delayed gratification, differ across cultures. Con-

sequently, adaptations essential to survival in one context may be maladap-

tive in another.

4. Children are active participants in their own development, reflecting

the intrinsic human drive to explore and master one’s environment. The

inborn drive to master the environment is a basic feature of human develop-

ment throughout the life cycle (White, 1959), as we illustrate throughout

Part II of this volume. Shortly after birth, children begin to learn about the

world through their remarkable capacities to create their own knowledge

from early experience. This inborn thrust is facilitated by the extent to

which their environments provide opportunities and supports for growth.

Parents and the general public wonder about which experiences are neces-

sary for healthy development to unfold. Must these experiences be costly?

Do they require expensive educational toys and early access to computers?

The simple answer to such questions is generally “no.” Given the drive of

young children to master their world, most developmentalists agree that the

full range of early childhood competencies can be achieved in typical, every-

day environments. A cabinet with pots and pans, for example, seems to

serve the same purpose as a fancy, “made for baby” musical instrument.

An extensive body of multidisciplinary research supports the notion of

powerful inborn tendencies toward mastery that are apparent in earliest

infancy. Piaget (1952) labeled this characteristic cognitive assimilation and

considered it to be a basic fact of life. Others have called it mastery motiva-

tion (e.g., MacTurk and Morgan, 1995), emphasizing the experience of

pleasure in performing newly acquired behaviors and skills. Fraiberg pointed

out that this developmental thrust enhances efforts to direct development

along positive pathways, commenting, “it’s a little bit like having God on

your side” (Fraiberg et al., 1980, p. 53). Reviewing previous research on

early development, Emde (1990) specified aspects of this developmental

thrust and proposed that they act as key ingredients for behavioral inter-

ventions throughout the life span. In this regard, all forms of early child-

hood intervention are most effective when they counteract obstacles

to growth and promote the expression of a child’s natural drive toward

mastery.

5. Human relationships, and the effects of relationships on relation-

ships, are the building blocks of healthy development. From the moment of

conception to the finality of death, intimate and caring relationships are the

fundamental mediators of successful human adaptation. Those that are

created in the earliest years are believed to differ from later relationships in

that they are formative and constitute a basic structure within which all

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28 FROM NEURONS TO NEIGHBORHOODS

meaningful development unfolds. Because many of the regulatory systems

that are essential for infant survival and emotional organization require

consistent caregiving attention, it has been said (perhaps too dramatically)

that without the caregiver-infant relationship, there would be no infant

(Winnicott, 1965).

The essential features of healthy, growth-promoting relationships in

early childhood are best embodied in the concepts of contingency and

reciprocity. That is to say, when young children and their caregivers are

tuned in to each other, and when caregivers can read the child’s emotional

cues and respond appropriately to his or her needs in a timely fashion, their

interactions tend to be successful and the relationship is likely to support

healthy development in multiple domains, including communication, cog-

nition, social-emotional competence, and moral understanding (Brazelton

et al., 1974; Emde, 1980; Stern, 1977).

Developmental or behavioral disturbances in infants and toddlers are

embedded in disturbances of the caregiver-infant relationship (Ainsworth,

1973; Bowlby, 1973; Sameroff and Emde, 1989). Because babies depend

for their survival on the care of adults, it is difficult, if not impossible, to

consider their problems independent from their relationships with their

primary caregivers. For example, a young child may be difficult to soothe,

but whether this characteristic expresses itself as a disorder that requires

therapeutic attention will depend on the way it affects and is handled by the

child’s primary caregivers. Some adults may view such behavior as over-

whelmingly negative (“he is spoiled, selfish, and unreasonable”), whereas

others may

see it as a positive trait (“she knows her own mind and won’t

settle for less than what she wants”). Most successful interventions, whether

they are primarily preventive or therapeutic, are based on facilitating that

relationship and helping both the child and the caregiver learn to adapt

successfully to each other’s individuality. These issues are taken up in more

detail in Chapters 9, 11, and 13.

6. The broad range of individual differences among young children

often makes it difficult to distinguish normal variations and maturational

delays from transient disorders and persistent impairments. Developmental

competencies vary significantly across a wide range of individual differ-

ences, and the rank ordering of children according to their abilities changes

over time. Within this broad continuum, it often can be difficult to make

clear distinctions among individual differences within a normative or typi-

cal range (e.g., variations in communication skills), transient delays related

to maturational lags (e.g., speech articulation errors), and diagnosed de-

velopmental disabilities (e.g., true disorders of language or cognition), espe-

cially in the early childhood years. A related issue is the fact that so many

defining symptoms for disorders are also nonspecific indications that some-

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INTRODUCTION 29

thing is not quite right. This applies to depression, inattention, overactivity,

and anxiety—all of which can be displayed by a child who has a fever or is

overly tired, as well as by a child with a specific disorder. In part, these

difficulties are related to the limitations of existing developmental mea-

sures. To a large extent, however, diagnostic dilemmas are inherent in the

complex and unpredictable nature of early childhood development (Boyce,

1996).

All children have built-in capacities to attain developmental goals in

multiple ways and under varying conditions. This is illustrated in the phe-

nomenon of alternative developmental pathways, which provides a useful

model for understanding the distinctive competencies that children develop

in diverse cultural contexts, as well as the different family patterns of

interaction that promote their unfolding (Erikson, 1950; Pumariega and

Cross, 1997).

The concept of alternative developmental pathways offers a framework

for viewing individual differences, maturational delays, and actual disabili-

ties as part of a unified continuum that applies to the development of all

children. The early child-caregiver relationship, for example, can be stressed

by either biological or environmental threats, yet the processes governing

the relationship are organized in a comparable manner, even for children

with significant impairments or for those whose development is at very high

risk (Cicchetti and Beeghly, 1990; Sameroff and Emde, 1989). Similarly, all

developmental transitions are susceptible to the adverse impacts of a wide

range of risk factors that can produce a sense of elevated uncertainty,

regardless of the nature of the child or the caregiving context (Wishart,

1993). Ultimately, such patterns are understood best when they are viewed

as variations within a common developmental framework.

Children born with significant biological impairments (e.g., blindness,

deafness, severe motor deficits) also attain a range of basic abilities, such as

representational thinking and language competence, in ways different from

those experienced by children without such limitations. Greater under-

standing of these alternative pathways can provide guidance for interven-

tionists in their attempts to facilitate the adaptive development of young

children with a wide variety of special needs, as well as in their efforts to

extend constructive support to their parents (Decarie, 1969; Fraiberg, 1977;

Gleitman, 1986). These issues are further discussed in the context of the

specific developmental tasks described in Part II.

7. The development of children unfolds along individual pathways

whose trajectories are characterized by continuities and discontinuities, as

well as by a series of significant transitions. The process of development is

essentially a process of change. In some cases (e.g., increasing memory

functions), that change appears to be gradual, cumulative, and continuous.

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In other cases (e.g., the beginning of expressive language and self-awareness

in the second year), the gains are so far-reaching that they represent a

qualitative discontinuity from what has come before (Brim and Kagan,

1980; Rutter and Rutter, 1993). Such transformations are often referred to

as developmental transitions. These transitional phases, which may be

either smooth or characterized by stress and turmoil, have been viewed as

important periods of psychological reorganization that provide useful op-

portunities for intervention (Brazelton, 1992). Developmental transitions

occur throughout the life span, but in the early childhood years they are

more frequent and involve profound psychobiological changes.

A developmental transition can be thought of as a time when change is

pervasive and enduring, and when it involves a major reorientation in how

a child relates to the environment. It is a time when the emotional commu-

nication between children and caregivers is particularly significant (Emde,

1998). Developmental transitions are periods of psychological disequilib-

rium that reflect elements of both the stage that is being completed and the

stage that is about to begin. The intense negativism of toddlers, who are

attempting to reconcile strong feelings of attachment to their parents and a

powerful drive for personal autonomy, is a familiar example of this com-

plex phenomenon. These issues are taken up in more detail in Part II.

8. Human development is shaped by the ongoing interplay among

sources of vulnerability and sources of resilience. Individual developmental

pathways throughout the life cycle are influenced by interactions among

risk factors that increase the probability of a poor outcome and protective

factors that increase the probability of a positive outcome (Garmezy et al.,

1984; Rutter, 2000; Werner, 2000). Risk factors may be found within the

individual (e.g., a temperamental difficulty, a chromosomal abnormality)

or the environment (e.g., poverty, family violence). Protective factors also

may be constitutional (e.g., good health, physical attractiveness) or envi-

ronmental (e.g., loving parents, a strong social network). The cumulative

burden of multiple risk factors is associated with greater developmental

vulnerability; the cumulative buffer of multiple protective factors is associ-

ated with greater developmental resilience. Sameroff, Seifer, Barocas, Zax,

and Greenspan (1987) have demonstrated that the total number of risk

factors in a child’s life is a better predictor of IQ scores than the specific

nature of those factors. The double burden of both biological and environ-

mental risk produces an unusually high level of vulnerability (Escalona,

1982; Parker et al., 1988; Shonkoff, 1982).

Some developmental pathways follow trajectories or patterns that are

deeply ingrained and thus less amenable to influences that may deflect them

in a positive or negative direction. Others are highly susceptible to such

risks and protective influences. Waddington (1966) compared these path-

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INTRODUCTION 31

ways to the valleys and ridges that are formed by a ball rolling downhill.

The further the ball rolls

along a given path, the deeper are the valleys and

the steeper are the ridges. Developmental characteristics that are embedded

in deeply chiseled trajectories (e.g., basic motor capacities, such as crawling

and walking) are less amenable to environmental modification and are

described as canalized. Other trajectories have valleys that are more shal-

low or ridges that are less steep, which leave them more susceptible to

change (e.g., basic self-care skills, early literacy). Ultimately, the extent to

which any existing pathway can be modified or redirected is determined by

both biological and environmental influences. The child’s own expecta-

tions, and those of the significant people in his or her life, often play an

important role in maintaining or changing direction. These concepts are

especially pertinent to the literature reviewed in Part III regarding the con-

texts for early development.

9. The timing of early experiences can matter, but, more often than

not, the developing child remains vulnerable to risks and open to protective

influences throughout the early years of life and into adulthood. Human

adaptation derives from both the rapid consolidation of essential capacities

and lifelong flexibility to adjust to changing circ*mstances (see Chapter 8).

Efforts to understand which aspects of development become set early on

and which remain open to change have been shaped by notions of critical

and sensitive periods, as well as by a growing research literature on the

malleability or plasticity of the human organism.

The concepts of both critical and sensitive periods refer to unique

episodes in development when specific structures or functions become espe-

cially susceptible to the influence of particular experiences (Bornstein, 1989;

Thompson, in press(a)). Although critical periods have been well described

for several behaviors in a variety of animal species (e.g., imprinting in

newborn geese), the term “sensitive period” is preferred when studying

humans because it implies less rigidity in the nature and timing of the

required experiences, as well as less inevitability in its developmental out-

come (Immelmann and Suomi, 1982). Current knowledge suggests that,

although developmental progress in some domains may be relatively more

amenable to facilitation or vulnerable to harm during certain periods in

comparison to others (see, for example, the discussion of institutionaliza-

tion in Chapter 9 and of family income in Chapter 10), advances can occur

at virtually any age.

The concept of developmental plasticity refers to the capacity of the

brain to reorganize its structure or function, generally in response to a

specific event or perturbation. Although it is determined fundamentally by

genetic modification, plasticity often comes about as a result of a change in

the environment (see Chapters 2 and 8). Times of developmental transition,

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32 FROM NEURONS TO NEIGHBORHOODS

which are often characterized by major alterations in person-environment

relationships, provide important opportunities for understanding this criti-

cal adaptive phenomenon. Neurodevelopmental plasticity varies inversely

with maturation. That is to say, there is more multipotentiality (i.e., greater

capacity for alternative developmental adaptations) in the early childhood

period than in the later years.

10. The course of development can be altered in early childhood by

effective interventions that change the balance between risk and protection,

thereby shifting the odds in favor of more adaptive outcomes. Although the

desire to learn, grow, and “become” is inherent in the biology of early

childhood, it is also a characteristic that is open to modification based on

individual experience. When the environment supports a child’s emerging

sense of agency (i.e., the feeling of being able to influence events and thus

having an impact on one’s own life), his or her motivation to act on the

world flourishes. When experience fails to support (or punishes) such ac-

tion, a child’s motivation diminishes, shifts, or finds problematic outlets.

Early environments that facilitate competence and a sense of personal effi-

cacy are more likely to foster children who do well. When opportunities for

agency are limited, psychological growth is more likely to be compromised.

A wide variety of early intervention policies and programs have been

designed to create growth-promoting environments for young children

whose development is threatened by biological vulnerability or adverse life

circ*mstances (see Chapter 13). Different models employ varying combina-

tions of strategies focused on providing direct experiences for the child,

influencing the behaviors of the child’s primary caregivers and/or working

directly on the child-caregiver relationship. The basic objective underlying

all interventions in the early childhood years is to increase the probability of

a more favorable developmental trajectory for each child. This is accom-

plished by attempting to identify and mitigate the influence of existing risk

factors, as well as to identify and enhance the buffering capacity of avail-

able protective factors. This often occurs in the context of specific therapeu-

tic or educational services. Individual goals are determined in terms of each

child’s and family’s baseline status in conjunction with an assessment of the

extent to which relevant risk and protective factors are susceptible to

change. In the final analysis, early childhood intervention is viewed most

appropriately as an individualized strategy designed to increase the prob-

ability of a desired outcome, and not as a developmental panacea for all

children under all circ*mstances. It is the art of the possible, based on the

science of early childhood development.

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INTRODUCTION 33

SCOPE OF THE STUDY

The committee’s charge to identify the implications of its scientific

review was directed at three interrelated goals: (1) to inform the design and

implementation of policies, services, and professional training to support

the health and development of young children and their families; (2) to

stimulate the formulation of an integrated research agenda to advance both

the basic science of early childhood development and the applied science of

early childhood intervention, extending from the prenatal period through

the preschool years; and (3) to educate the public about state-of-the-art

knowledge regarding human development during early childhood.

The committee did not set out to produce a comprehensive handbook

on early childhood development, nor did we seek to provide explicit par-

enting advice. We selected topics that are especially pertinent to current

debates about the early childhood years and sought to help readers under-

stand young children rather than to offer directive statements about how

to raise them. Indeed, with such understanding comes humility about the

complexity of the task undertaken by anyone who brings up a child, and

an appreciation for the value of a firm grounding in “what develops?”

and “how?” as a departure point for highly personal decisions involved in

day-to-day childrearing.

To select the issues on which it would focus, the committee conducted

a series of interviews with practitioners and policy makers to assess their

views of the most pressing issues facing contemporary early childhood

practice and policy, as well as with scientific colleagues in fields ranging

from basic neuroscience to anthropology and sociology. The committee

also reviewed a broad range of previous reports produced by the National

Research Council and the Institute of Medicine and, with few exceptions

(e.g., child care, prenatal

alcohol exposure), did not conduct new reviews of

areas addressed previously (see Appendix A for a listing of pertinent re-

ports). Appendix A includes a number of reports that address issues of

physical health and nutrition that, while not explicitly addressed in this

report, are a vitally important foundation for every aspect of development

we discuss. The science summarized in this report reflects the expertise and

judgment of the members of the committee, who were themselves selected

for their breadth of knowledge and interdisciplinary scope.

The analyses that contributed to this report draw on a variety of

sources. The committee reviewed a wide body of research through targeted

literature searches and direct correspondence with investigators known for

their work on specific topics. Between October 1998 and February 2000,

the committee met six times to identify critical issues, analyze available

data, discuss research findings, seek additional information on specific ar-

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34 FROM NEURONS TO NEIGHBORHOODS

eas of concern, formulate conclusions and recommendations, and prepare

this report. Three additional subcommittee meetings were convened to dis-

cuss pertinent literatures on neuroscience, culture and early human devel-

opment, and methodological issues. Three workshops—on home visiting

interventions, precursors of antisocial behavior, and the science of early

childhood intervention (National Research Council and Institute of Medi-

cine, 2000)—and five commissioned papers1 also contributed valuable sci-

entific input to the committee’s work.

PLACING THE STUDY IN CONTEXT

One hundred years ago, the transition from the 19th to the 20th cen-

tury marked a time of significant energy, creativity, and attention to the

health and well-being of the nation’s children. The overlapping emergence

of child development as a focus within the field of psychology, pediatrics as

a specialization within the practice of medicine, and child welfare as a

defined domain within the purview of both the judicial system and the

world of social work provides just a few examples of the extent to which

the distinctive needs of children began to appear more clearly on the social

and political agenda (National Research Council, 1981, 1982). In 1912,

Congress established the Children’s Bureau in the Department of Labor,

which proceeded to conduct studies in such diverse areas as infant mortal-

ity, day care, institutional care, and mental retardation (Lesser, 1985). Ten

years later, as a growing database documented the strong association be-

tween socioeconomic factors and infant and maternal deaths, public health

nursing services and state child hygiene divisions were expanded under the

provisions of the Sheppard-Towner Act of 1921 (Steiner, 1976).

As the crown jewel of the New Deal, the passage of the Social Security

Act of 1935 formalized an expanded federal responsibility for the health

and well-being of children and their mothers. Title V of the act authorized

financial assistance to the states to support: (1) a broad array of maternal

and child health services, including prenatal care, well-baby clinics, immu-

nization programs, and nutrition services, with a special emphasis on

underserved rural and low-income populations; (2) comprehensive services

for “crippled children”; and (3) a range of child welfare services for the care

and protection of homeless, dependent, and neglected youngsters (Magee

1Topics were: the demographics of the birth to five age group, atypical language develop-

ment, the developmental consequences of community violence, regulation of attention and

executive function in young children, and the effects of prematurity on early brain develop-

ment. In addition, over two dozen experts in the area of culture and early development were

invited to respond to a brief questionnaire about key topics developed by the committee.

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INTRODUCTION 35

and Pratt, 1985). Another provision of the act, Aid to Dependent Children

(later renamed Aid to Families with Dependent Children) ensured a federal

entitlement to a guaranteed baseline of economic security for vulnerable

children and their mothers.

Three decades after the onset of the New Deal, under the broad um-

brella of the Great Society and the War on Poverty, the modern era of early

childhood intervention was launched with the creation of Head Start and

the initiation of the Handicapped Children’s Early Education Program

(Smith and McKenna, 1994; Zigler and Valentine, 1979). Whereas Title V

of the Social Security Act had strengthened the nation’s medical focus on

the consequences of low income and childhood disability, the policies of the

1960s spearheaded an education strategy. Fifteen years later, during a pe-

riod of significant reduction in federal social programs and devolution of

authority to the states, Head Start continued to be funded as a part of the

government’s “safety net,” and a new federal entitlement to early interven-

tion services for infants and toddlers with disabilities was enacted under

Part H of the Education for All Handicapped Children Act Amendments of

1986 (Public Law 99-457), and reauthorized in 1997 as Part C of the

Individuals with Disabilities Education Act (Public Law 105-107) (Meisels

and Shonkoff, 2000).

The current social, economic, and political contexts within the United

States in which this report will be read and interpreted have once again

changed. In recent years, federal legislation has been enacted to expand the

financing of child health care through the State Children’s Health Insurance

Program under Title XXI of the Social Security Act (Public Law 105-33),

yet the 60-year entitlement to welfare support for families with young

children has been terminated by the Personal Responsibility and Work

Opportunity Reconciliation Act of 1996. Greater investment in education

reform garners strong public support, universal school readiness is ranked

first among the nation’s education goals, and the demand for higher stan-

dards and stricter accountability in the public schools is widely endorsed.

And yet, despite two high-profile White House conferences on child care

and early childhood development and significant increases in public fund-

ing for early child care and education at both the federal and state levels,

there is still widespread and well-entrenched resistance to the formulation

and enforcement of more rigorous standards for child care providers and

the settings in which they work. And despite the creation and expansion of

Early Head Start for infants and toddlers, services for 3- and 4-year-olds are

still available to less than half of the eligible children in the United States,

more than 30 years after the opening of the first Head Start center in 1965

(Meisels and Shonkoff, 2000).

Beyond specific government policies and programs, the context of this

report is reflected in a set of highly interrelated social, economic, and

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36 FROM NEURONS TO NEIGHBORHOODS

political challenges presently facing children, their parents and other care-

givers, and U.S. society in general. These include: (1) dramatic changes in

the nature of work, an increasingly strong link between education and

employability, and greater difficulty for families at all income levels in

balancing workplace and family responsibilities; (2) ongoing increases in

the racial and ethnic diversity of the U.S. population and the persistence of

significant racial and ethnic disparities in health and developmental out-

comes;

(3) the persistent poverty of young children and a growing gap

between the wealthy and the poor; (4) continued high rates of community

and family violence, as well as serious mental health problems that impose

significant burdens on family functioning; (5) an increased reliance on mar-

ket solutions to address complex social problems; (6) the devolution of

some important responsibilities for the implementation of child and family

policy to the state and local levels; and (7) conflicting views about the role

of government and the balance between public and personal responsibility

for the health and well-being of children.

The release of this report also comes at a somewhat sensitive time in the

politics of early childhood intervention in the United States. Evaluations of

a wide range of model programs and community-based replications have

produced results both encouraging and disappointing, posing a critical chal-

lenge to those who are seeking to understand the conditions under which

success is more likely than failure. This is also a time of significant expan-

sion in state and local initiatives designed to improve the life chances of

very young children. Fueled by headlines about the importance of the early

years, as well as by increased national interest in school readiness, educa-

tion reform, and the early roots of antisocial behavior and violent crime,

this heightened public concern raises critical questions about which invest-

ments are most likely to make a significant difference for the most vulner-

able young children. In this context, the most important task facing the

committee is not to differentiate specific intervention programs that “work”

from those that do not. Rather, it is to provide a scientifically grounded

portrait of the most important achievements of early childhood and the

environmental conditions that either promote or impede their accomplish-

ment, and to point to directions for both action and further research to-

ward those ends.

This report addresses two complementary agendas. The first is focused

on the future and asks: How can society use knowledge about early child-

hood development to maximize the development of the nation’s human

capital and ensure the ongoing vitality of its democratic institutions? The

second is focused on the present and asks: How can the nation use knowl-

edge to nurture, protect, and ensure the health and well-being of all young

children as an important objective in its own right, regardless of whether

measurable returns can be documented in the future? The first agenda

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INTRODUCTION 37

speaks to society’s economic, political, and social interests. The second

speaks to its ethical and moral values. The committee is clear in our respon-

sibility to speak to both.

ORGANIZATION OF THE REPORT

The organization of this report reflects its charge. Part I sets the stage

for understanding the material that follows. This introduction has pre-

sented an overview of the core concepts that guided the committee’s

inquiry. Chapter 2 takes up a reconceptualization of the long-standing

debate about the interaction between nature and nurture. Chapter 3 sum-

marizes current thinking about the multifaceted concept of culture and its

role in early human development, and Chapter 4 raises important method-

ological issues regarding efforts to explore questions about causality in

early development and early intervention.

Part II addresses the central question of the nature of early develop-

ment. What develops during the earliest months and years of life? What are

the major behavioral and developmental tasks of the early childhood pe-

riod? When should we worry? This part of the report starts with the child’s

emerging capacity for self-regulation, reflecting a shift in what develop-

mentalists now believe to be a hallmark of early development (Chapter 5).

Next, we turn to the remarkable accomplishments in language and learning

that characterize this age period (Chapter 6) and the critical challenges

associated with getting along with other children (Chapter 7), both of

which represent areas of heightened interest on the part of parents, practi-

tioners, and policy makers alike. Chapter 8 provides an updated review of

research on early brain development. It comes last, reflecting the fact that

developmental neuroscience is a recent addition to the study of the child.

Furthermore, processes of brain development are better understood when

considered in relation to the significant and concurrent emotional, mental,

and social advances of early childhood.

Part III turns to the role of early environments as they shape early

development. The chapters review research on the multiple, overlapping

contexts in which development unfolds, beginning with the most active

ingredient of early environmental influences, namely the parent-child rela-

tionship (Chapter 9). We then discuss the contribution of the economic

niche occupied by the family (Chapter 10), the influence of child care

(Chapter 11), and the role of the community in which the child lives (Chap-

ter 12). Together, these chapters paint a vivid picture of the environments

and experiences that foster or impede adaptation and well-being. Chapter

13 is a critical overview of the scientific foundations of early childhood

intervention, thereby complementing what is known about early develop-

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38 FROM NEURONS TO NEIGHBORHOODS

ment as it unfolds naturally over time with a view based on efforts to alter

its course.

The committee’s charge to draw out the implications of its research

review is addressed in the final chapter (Chapter 14), which provides con-

clusions and makes recommendations for policy, practice, and professional

development, as well as for research.

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Rethinking Nature

and Nurture

s developmental psychologists stand at the threshold

of a new era in understanding the biological bases for

human growth and continue to address fundamental questions about

parenting influences, it is time for a new appreciation of the coactivity of

nature and nurture in development. Beginning at the moment of concep-

tion, hereditary potential unfolds in concert with the environment. The

dynamic interplay between gene action and environmental processes con-

tinues throughout life. Although their influences are so often distinguished

in ancient philosophy and modern science, the inseparability of nature and

nurture has profound implications for how we study and understand hu-

man development.1 In this chapter, we trace these implications drawing

first on the literature on developmental behavioral genetics, then undertak-

ing a discussion of molecular genetics. We close with a brief discussion of

brain development, foreshadowing the focused attention that is given to

this topic in Chapter 8.

Nature and nurture are partners in how developing people interact

with the surrounding environment. Nature and nurture are partners also in

1Although this chapter focuses primarily on genetic influences that contribute to individual

differences among children, it is essential to remember that genetic influences also account for

the characteristics that humans share as a species, such as upright walking and language.

Indeed, the inseparability of nature and nurture is also reflected in the fact that both nature

and nurture are required for children to acquire these and other attributes that all humans

share.

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of Early Childhood Development

40 FROM NEURONS TO NEIGHBORHOODS

the transactions between the gene2 and the variety of internal environments

that surround it within the body (Greenough, 1991; Greenough and Black,

1992). The environment of the cell influences which of the tens of thou-

sands of genes are expressed to affect cell characteristics. Hormones and

growth factors in the cell can turn some genes on and turn others off. These

substances can arise from the nucleus of the cell, its cytoplasm, or the

surrounding cells or organs. The substances that influence gene expression

arise also from the functioning of other genes within the cell (so-called

regulator genes) and the products of earlier protein synthesis.

It is impossible to think of gene expression apart from the multiple

environments in which it occurs. It is impossible to think of the manifesta-

tion of hereditary potential independently of the hierarchy of environments

that shape its appearance. It is impossible to think of an organism that

interacts with the environment without considering the genotypical unique-

ness of that individual. It is impossible, in short, to consider nature apart

from nurture.

Why, then, are these two forces of human development so persistently

differentiated in efforts to understand human development? From ancient

Platonic and Confucian philosophy to the present, the dichotomy between

inherited capabilities and environmental incentives and pressures has guided

human self-understanding in Western and Eastern thought. All contempo-

rary scientists acknowledge the interaction of heredity and environment

(see Elman et al., 1996, for a recent and sophisticated version of the

interactionist view). Yet an emphasis on whether hereditary constraints or

environmental incentives are the preeminent influence in human develop-

ment can still be observed not only in scholarship in psychology but also,

more significantly, in public discourse concerning the importance of

parenting and early education, and in policy debates about early interven-

tion programs, family support, delinquency and criminality, and other is-

sues of child and family policy.

2Within the nucleus of every cell are chromosomes containing genes, which are segments of

DNA. Genes direct the synthesis of proteins that are incorporated into the structure of the

cell, regulate its biochemistry, and guide other genetic activity. Genes ultimately affect physi-

cal and behavioral characteristics through these influences on the cells within every living

being. Although each cell contains genes that are identical to the genes of every other cell, not

all genes function in the same way, and this accounts for why cells function differently from

one another. Some genes act continuously, for example, while other genes in the same cells

turn on temporarily, and others are never expressed. As one colorful description notes, if each

gene is represented as a light bulb that is either activated or not, we would see a distinct

twinkling of lights within each cell during its normal functioning (Leger, 1992). This is why

organisms can have trillions of cells, all of which have the same DNA but many different

forms and functions.

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RETHINKING NATURE AND NURTURE 41

It is time to reconceptualize nature and nurture in a way that empha-

sizes their inseparability and complementarity, not their distinctiveness: it is

not nature versus nurture, it is rather nature through nurture. If gene

expression is inconceivable apart from the environment, then it is useless

and potentially misleading to try to finely distinguish the relative impor-

tance of nature and nurture in the course of human development. Nature is

inseparable from nurture, and the two should be understood in tandem.

Moreover, by contrast with a traditional view that heredity imposes limita-

tions and environments induce change in developmental pathways, research

in developmental psychobiology shows that the coactivity of nature and

nurture accounts for both stability and malleability in growth. This view is,

indeed, one important way of integrating the science of early childhood

development, and it is also reflected in recent scientific advances in some of

the research fields that are currently generating greatest interest among

developmental scientists: developmental behavioral genetics, molecular ge-

netics, and brain development.

DEVELOPMENTAL BEHAVIORAL GENETICS

In animal species, the importance of genetic influences on behavior can

often be studied directly through selective breeding research. In humans,

less intrusive procedures are necessary, and for the past several decades

developmental behavioral genetics has provided a powerful means of un-

derstanding the strength of heritable influences on individual differences in

human development, and the environmental contexts in which they are

expressed (see Lemery and Goldsmith, 1999; Plomin et al., 1997a; and

Rutter et al., 1999a, for overviews of this field). By taking advantage of

naturally occurring variation in genotypes and environments, behavioral

geneticists seek to partition behavioral variability into its genetic and envi-

ronmental components and describe their interaction.

They have two primary research strategies for doing so. In adoption

research, genetic contributions are estimated by comparing the characteris-

tics of an adoptive child with those of the birth mother (to whom the child

is genetically related, but they do not share an environment) and the adop-

tive mother (who shares the child’s environment, but not genes). Some-

times biologically related and unrelated siblings are also studied. The sec-

ond approach is twin research. Because identical (monozygotic) twins are

genetically identical, comparing the similarity of their characteristics with

those of fraternal (dyzygotic) twins, who on average share half their genes,

is another way of estimating genetic contributions.

Twin and adoption research designs each have assumptions or limita-

tions that can make the interpretation of findings difficult and sometimes

controversial. In adoption research, for example, prenatal influences (e.g.,

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42 FROM NEURONS TO NEIGHBORHOODS

teratogenic exposure) can also account for the resemblance of biological

mothers to their offspring, and this can inflate estimates of genetic contri-

butions. In addition, adoption designs assume that the selective placement

by adoption agencies of children into the homes of parents who are like

them (or their biological parents) does not occur. It is possible to estimate

the potential biases introduced by selective placement or prenatal influ-

ences, but this is very difficult in most research designs. Twin studies also

have certain assumptions: that identical twins do not share a more similar

environment than do fraternal twins, and that the development of twin

pairs is fairly representative of the growth of children in general. These

assumptions, too, have been tested, with some researchers concluding that

these assumptions are valid and others disagreeing.

Adoption and twin studies each provide means of estimating quantita-

tively the proportion of variance in human characteristics that is attribut-

able to heredity and to the environment, and of examining how these

influences interact in development. During the past decade, developmental

behavioral genetics research has expanded considerably in sophistication

and analytic methods, using variations on the basic adoption and twin

research designs (sometimes combining these methods) and employing struc-

tural equations modeling and

other quantitative model-fitting methods for

estimating genetic and environmental contributions to behavioral variabil-

ity. These efforts have yielded important new insights into the heritability

of individual differences in cognitive abilities, extraversion, emotionality,

self-control, and other characteristics and have shown how inherited pro-

pensities to childhood disorders like autism, schizophrenia, attention deficit

hyperactivity disorder, and antisocial behavior need to be considered by

practitioners (see reviews by Plomin et al., 1997b and Rutter et al., 1999b).

Even more important is how this research contributes to an apprecia-

tion of how nature and nurture influence development in concert. A recent

study of the development of antisocial behavior in children by Ge, Conger,

Cadoret, Neiderhiser, Yates, Troughton, and Stewart (1996) is exemplary.

Using an adoption design, these researchers found that when biological

parents had substance abuse problems or antisocial personality disorder,

their adopted children were much more likely to be hostile and antisocial

than were adoptees from untroubled biological parents. Children’s inher-

ited antisocial tendency may have been manifested as difficult tempera-

ments, problems with emotional self-control, impulsivity, or other difficul-

ties. It was not surprising, therefore, that children’s antisocial tendency was

also associated with greater harshness and less nurturance and involvement

by their adoptive mothers and fathers. This illustrates how children’s

inherited characteristics can evoke complementary responses from their

parents (called “gene-environment correlation”).

Parents and children in these adoptive families influenced each other.

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RETHINKING NATURE AND NURTURE 43

Children with greater hostility tended to evoke more severe disciplinary

responses, but harsh discipline also tended to exacerbate children’s antiso-

cial behavior. Parents’ treatment of their adoptive offspring was influenced

not only by the child’s demandingness, but also by influences that were

found to be independent of the child’s inherited characteristics, such as the

quality of the parents’ marital relationship (see Figure 2-1). Thus the devel-

opment of antisocial behavior in children was influenced by heritable char-

acteristics—which altered the childrearing climate of the home—and by

family influences that arose independently of the child. Other studies offer

a similar portrayal of the coactivity of nature and nurture in human devel-

opment (see Cadoret et al., 1996; O’Connor et al., 1998; Pike et al., 1996;

and Reiss, 1997).

These studies have important practical implications. Since parenting

and other environmental influences can moderate the development of in-

herited tendencies in children, efforts to assist parents and other caregivers

to sensitively read a child’s behavioral tendencies and to create a supportive

context for the child are worthwhile. A good fit between environmental

conditions and the child’s characteristics is reflected, for example, in family

routines that provide many opportunities for rambunctious play for highly

Biological parents'

psychiatric disorders

Adoptive child's

antisocial behaviors

Adoptive mother's

disciplinary practices

Adoptive parents'

marital warmth

FIGURE 2-1 Model of hereditary and environmental influences on children’s anti-

social behaviors. SOURCE: Adapted from Ge et al. (1996).

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44 FROM NEURONS TO NEIGHBORHOODS

active children, or in child care settings with quiet niches for shy children to

take a break from intensive peer activity. Thoughtfully designed caregiving

routines can incorporate helpful buffers against the development of behav-

ior problems among children with inherited vulnerabilities by providing

opportunities for choice, relational warmth, structured routine, and other

assists. Interventions to assist children at risk for other psychological disor-

ders must also be individualized and emphasize the creation of a good fit

between inherited vulnerabilities and behavioral demands, especially for

children at greater heritable risk for problems like antisocial behavior,

depression, and attention deficit hyperactivity disorder.

Heritability

Twin and adoption research designs each permit behavioral geneticists

to calculate a heritability statistic (h2), which is an estimate of the propor-

tion of variability in individual characteristics that is due to genetic differ-

ences. A heritability of .45, for example, indicates that 45 percent of the

measured variability in a particular characteristic is due to genetic differ-

ences in the sample. There are comparable statistics that estimate environ-

mental contributions to individual characteristics. Unfortunately, the dis-

tillation of many complex findings in behavioral genetics research to a

single heritability figure has led to considerable misunderstanding of its

meaning, especially when heritability estimates in the range of 30 to 70

percent are derived from studies of the genetic contributions to individual

differences in intelligence, personality, and psychopathology. This misun-

derstanding derives, in part, from the traditional tendency to seek to distin-

guish the effects of nature and nurture in development. Thus it is important

to appreciate several principles:

• Heritability estimates are proportions based on environmental as

well as genetic diversity. As a proportion, heritability reflects the extent of

environmental influences as well as genetic influences. On one hand, if the

environment could be made the same for everyone, heritability would inevi-

tably be large because individual differences would then be due entirely to

genetic factors (Lemery and Goldsmith, 1999; Plomin et al., 1997b). On

the other hand, if people are studied in environments with diverse influ-

ences on them (varying significantly in socioeconomic status, ethnicity, or

culture, for example), environmental contributions are magnified and heri-

tability is lower. In short, a heritability estimate is uninterpretable without

an appreciation of the extent of the environmental variability that also

influences behavior in a particular sample.

• Heritability estimates are sample- and context-specific. Heritability

estimates reflect the environmental diversity of the sample under study, as

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RETHINKING NATURE AND NURTURE 45

well as their genetic diversity. Heritability estimates tend to be higher in

samples with greater variability in relevant genetic influences and, con-

versely, lower in samples that are genetically hom*ogeneous. Because re-

search samples can vary in both their environmental and genetic diversity, a

heritability estimate must always be understood as pertaining to observed

differences between individuals in a particular sample at a particular time in

a specific environment.

• Heritability estimates change with development. A characteristic

that is highly heritable at one age may not be particularly heritable at

another (Lemery and Goldsmith, 1999). There are many reasons for this,

including the changes that occur in gene activation with human growth,

changes in environmental influences with increasing age, and changes in the

nature of a person’s engagement with the environment over time. The

heritability of variations in general cognitive ability tends to increase with

age, for example, as does the heritability of certain behavioral difficulties,

such as those associated with antisocial behavior (Goldsmith

the broad community of science and technology with the

Academy’s purposes of furthering knowledge and advising the federal government.

Functioning in accordance with general policies determined by the Academy, the

Council has become the principal operating agency of both the National Academy

of Sciences and the National Academy of Engineering in providing services to the

government, the public, and the scientific and engineering communities. The Coun-

cil is administered jointly by both Academies and the Institute of Medicine. Dr.

Bruce M. Alberts and Dr. William A. Wulf are chairman and vice chairman, respec-

tively, of the National Research Council.

National Academy of Sciences

National Academy of Engineering

Institute of Medicine

National Research Council

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From Neurons to Neighborhoods: The Science of Early Childhood Development

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From Neurons to Neighborhoods: The Science of Early Childhood Development

COMMITTEE ON INTEGRATING THE SCIENCE

OF EARLY CHILDHOOD DEVELOPMENT

JACK P. SHONKOFF (Chair), Heller Graduate School, Brandeis University

DEBORAH L. COATES, Department of Psychology, The City University

of New York

GREG DUNCAN, Institute for Policy Research, School of Education and

Social Policy, Northwestern University

FELTON J. EARLS, Department of Child Psychology, Harvard Medical

School

ROBERT N. EMDE, Department of Psychiatry, University of Colorado

Health Sciences Center

YOLANDA GARCIA, Children’s Services, Santa Clara County Office of

Education

SUSAN GELMAN, Department of Psychology, University of Michigan

SUSAN J. GOLDIN-MEADOW, Department of Psychology, University

of Chicago

WILLIAM T. GREENOUGH, Departments of Psychology and Cell and

Structural Biology, University of Illinois at Champaign-Urbana

RUTH T. GROSS, Department of Pediatrics (emeritus), Stanford

University Medical School

MEGAN GUNNAR, Institute of Child Development, University of

Minnesota

MICHAEL GURALNICK, Center on Human Development and

Disability, University of Washington

ALICIA F. LIEBERMAN, Department of Psychiatry, University of

California at San Francisco

BETSY LOZOFF, Center for Human Growth and Development,

University of Michigan

BRIAN MacWHINNEY, Department of Psychology, Carnegie Mellon

University*

RUTH MASSINGA, The Casey Family Program, Seattle, Washington

STEPHEN RAUDENBUSH, School of Education, University of Michigan

ROSS THOMPSON, Department of Psychology, University of Nebraska

CHARLES A. NELSON (liaison from the MacArthur Foundation/

McDonnell Foundation Research Network on Early Experience and

Brain Development), Institute of Child Development, University of

Minnesota

DEBORAH A. PHILLIPS, Study Director

NANCY GEYELIN MARGIE, Research Assistant

RONNÉ WINGATE, Senior Project Assistant

*Resigned October 1998.

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From Neurons to Neighborhoods: The Science of Early Childhood Development

BOARD ON CHILDREN, YOUTH, AND FAMILIES

JACK P. SHONKOFF (Chair), Heller Graduate School, Brandeis

University

EVAN CHARNEY (Vice Chair), Department of Pediatrics, University of

Massachusetts Medical Center

JAMES BANKS, Center for Multicultural Education, University of

Washington

SHEILA BURKE, John F. Kennedy School of Government, Harvard

University

DAVID CARD, Department of Economics, University of California,

Berkeley

DONALD COHEN, Department of Child Psychiatry, Yale University

MINDY FULLILOVE, Department of Clinical Psychobiology, Columbia

University

KEVIN GRUMBACH, Department of Family and Community Medicine,

University of California, San Francisco

MAXINE HAYES, Community and Family Health, Department of

Health, Olympia, Washington

MARGARET HEAGARTY, Department of Pediatrics, Harlem Hospital

Center, Columbia University

RENÉE JENKINS, Department of Pediatrics and Child Health, Howard

University Hospital

SHEILA KAMERMAN, School of Social Work, Columbia University

HARRIET KITZMAN, School of Nursing, University of Rochester

SANDERS KORENMAN, School of Public Affairs, Baruch College

HONORABLE CINDY LEDERMAN, Circuit Court Judge, Juvenile

Division, Dade County, Florida

SARA McLANAHAN, Office of Population Research, Princeton

University

VONNIE McLOYD, Department of Psychology, University of Michigan,

Ann Arbor

PAUL NEWACHECK, Institute of Health Policy Studies and Department

of Pediatrics, University of California, San Francisco

GARY SANDEFUR, Department of Sociology, University of Wisconsin,

Madison

RUTH STEIN, Department of Pediatrics, Albert Einstein College of

Medicine

PAUL WISE, Department of Pediatrics, Boston Medical Center

RUTH T. GROSS (liaison from the Board on Health Promotion and

Disease Prevention, Institute of Medicine), Department of Pediatrics

(emeritus), Stanford University

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From Neurons to Neighborhoods: The Science of Early Childhood Development

ELEANOR MACCOBY (liaison from the Commission on Behavioral and

Social Sciences and Education, National Research Council),

Department of Psychology (emeritus), Stanford University

WILLIAM ROPER (liaison from the Institute of Medicine), School of

Public Health, University of North Carolina, Chapel Hill

MICHELE D. KIPKE, Director

ELENA O. NIGHTINGALE, Scholar-in-Residence

MARY GRAHAM, Associate Director, Dissemination and

Communications

MARY STRIGARI, Administrative Associate

vii

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From Neurons to Neighborhoods: The Science of Early Childhood Development

Acknowledgments

rom Neurons to Neighborhoods is the product of a

two-and-a-half-year project during which 17 indi-

viduals, as a committee, evaluated and integrated the current science of

early childhood development. In view of the wide range of scientific and

policy considerations that fall within the scope of the committee’s mandate,

it is particularly significant that the funding for this project was provided by

a broad diversity of public and private sponsors: Administration for Chil-

dren and Families, Administration on Children, Youth, and Families, Assis-

tant Secretary for Planning and Evaluation, Centers for Disease Control

and Prevention, Maternal and Child Health Bureau of the Health Resources

and Services Administration, National Institute for Child Health and Hu-

man Development, National Institute of Mental Health, National Institute

of Nursing Research, and the Substance Abuse and Mental Health Services

Administration, all of the U.S. Department of Health and Human Services;

Office of Special Education Programs in the U.S. Department of Education;

The Commonwealth Fund; Irving B. Harris Foundation; Heinz Endow-

ments; and Ewing Marion Kauffman Foundation. The committee wishes to

express particular appreciation to Duane Alexander, director of the Na-

tional Institute of Child Health and Human Development, and Ann

Rosewater, regional director of the U.S. Department of Health and Human

Services for Region IV, who played a critical role in organizing an early

meeting with potential federal sponsors and demonstrated unwavering faith

in the ability of the committee to address its very ambitious charge.

Beyond the expertise and diligence of the committee, we had the ex-

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x ACKNOWLEDGMENTS

traordinary good fortune of working with a number of highly knowledge-

able people who shared our enthusiasm for this project.

and

Gottesman, 1996; Plomin et al., 1997b). Heritability estimates are thus not

consistent over the course of development.

• Perhaps most important, heritability estimates describe what is in a

particular population at a particular time, rather than what could be

(Plomin et al., 1997b). Changes in either genetic influences or environmen-

tal influences are likely to alter the relative impact of heredity and environ-

ment on individual characteristics. Phenylketonuria is a highly heritable

genetic disorder that leads to mental retardation. But with a combination

of early detection and environmental interventions, retardation can be com-

pletely prevented (Birch et al., 1992). Thus contrary to the common belief

that highly heritable characteristics are impervious to environmental modi-

fication, interventions that alter the relevant environment—such as educa-

tional opportunities, therapeutic support, improved nutrition—can signifi-

cantly alter the development of that characteristic.

Moreover, it is important to remember that a heritability estimate de-

scribes influences on individual differences in a characteristic. Environmen-

tal influences can have a profound effect on that characteristic, however,

even when heritability is high. During the past century, for example, there

have been significant increases in average height owing to improved nutri-

tion and medical care, even though individual differences in height are

strongly influenced by heredity. This is because environmental changes

(such as improved diet and medical care) have markedly increased average

height from one generation to the next, while individual differences in

height have remained highly heritable (i.e., smaller parents still have smaller

children; see Figure 2-2). In a similar manner, other research (see Chapter

10) indicates that the socioeconomic status of adoptive homes has a power-

ful effect in elevating the IQ scores of adopted children, even though the

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46 FROM NEURONS TO NEIGHBORHOODS

c 4

c 3

c 2

c 1

Height

Parent generation

(poor nutrition,

medical care)

Child generation

(improved nutrition,

medical care)

FIGURE 2-2 Illustration of the effect of environmental changes on group differenc-

es and genetic influence on individual differences over time. NOTE: Each line

represents a family lineage, with P representing parents, and c representing off-

spring.

heritability of individual differences in IQ remain high (see Maccoby, 1999;

Schiff et al., 1982).

High heritability therefore does not mean low malleability. Environ-

mental interventions—which can include improved education, health care,

nutrition, and caregiving—can significantly improve developmental out-

comes for children, even though individual differences in those outcomes

may be strongly influenced by genetic processes. Heritability does not

imply constraints on change. It is instead more relevant to appreciating

how developmental outcomes can be changed. In particular, heritability

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RETHINKING NATURE AND NURTURE 47

may be relevant to considering the kinds of interventions that might be

most effective in relation to the genetically based characteristics of children.

Some developmental behavioral genetics researchers are dissatisfied,

however, with the heritability estimate because it provides a quantitative

but frequently misunderstood index of genetic influence that distracts at-

tention from the ways that behavioral genetics research can contribute to a

better understanding of risk and protective factors in development (e.g.,

Rutter, 1997; Rutter et al., 1999a; Wahlsten, 1990; Wahlsten and Gottlieb,

1997). An authoritative review of this field noted (Rutter, 1997:391):

It has gradually come to be accepted that the precise quantification of

heritability has little value because it provides no unambiguous implica-

tions for theory, policy, or practice. . . . There is little to be gained by

merely quantifying the relative importance of the contributions of ge-

netic and environmental influences because any estimates will be specif-

ic to the population studied and will be subject to change if environmen-

tal circ*mstances alter.

Shared and Nonshared Environmental Effects

Research in developmental behavioral genetics has also elucidated fea-

tures of environmental influence on individual differences. In particular,

researchers have helpfully distinguished between shared and nonshared

environmental influences. Shared environmental influences are those that

make individuals similar in their common environment. Nonshared envi-

ronmental influences are those that distinguish among individuals within

the same environment. Within a family, for example, shared environmental

influences make siblings alike independent of their genetic similarity, while

nonshared environmental influences make siblings different independent of

genetic factors. For instance, parental divorce is a source of shared environ-

mental influence if siblings within the family are affected similarly by this

event (e.g., because of moving to a new neighborhood, loss of contact with

one parent). Parental divorce can also be a source of nonshared environ-

mental influence if siblings are affected differently by the same event (e.g.,

older and younger children may interpret their parents’ divorce differently).

This example illustrates how the terms “shared” and “nonshared” refer not

to events or people, but to the effects they have on different children within

the family.

Both shared and nonshared environmental influences can be estimated

from adoption and twin research designs, although in different ways and

with different assumptions. Within each design, however, shared and

nonshared environmental effects are inferred from the resemblances among

genetically related family members and are rarely observed directly or ex-

perimentally manipulated. This has caused some scholars to criticize how

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48 FROM NEURONS TO NEIGHBORHOODS

shared and nonshared environmental influences are estimated (see, e.g.,

Baumrind, 1993; Rutter et al., 1999a) and to caution that direct measure-

ment is necessary before firm conclusions can be drawn about shared and

nonshared influences (e.g., Plomin et al., 1997b).

Like heritability estimates, the difference between shared and nonshared

environmental influences is often misunderstood. Some studies have shown,

for example, that within families the most important environmental influ-

ences are nonshared, making siblings different from each other (Plomin and

Daniels, 1987; Rowe, 1994). Some commentators have interpreted this to

mean that conventional portrayals of parenting influences (such as the view

that parents who use reasoning and gentle sanctions raise responsible chil-

dren, or that parents who read frequently inspire their offspring to do so)

are no longer valid because the important parental influences are those that

make siblings different rather than alike in their characteristics (e.g., Rowe,

1994; Scarr, 1992; see also Harris, 1995, 1998). But parenting influences

have long been understood by developmental scientists as sources of differ-

ences between siblings for many reasons (Collins et al., 2000; Maccoby,

1999). Parents develop unique and special relationships with each of their

offspring, their childrearing efforts are experienced differently by siblings

because of each child’s distinctive characteristics (e.g., temperament, per-

sonality, gender, age), and good parents take

these characteristics into ac-

count in adapting their general childrearing practices to their specific en-

counters with each child (Grusec and Goodnow, 1994). Indeed, even when

parents use the same child-rearing practices with different children, they

evoke different reactions because of each child’s temperament, age, and

other characteristics. These influences contribute to why, as every parent

knows, siblings develop unique and distinctive characteristics, and parental

practices help to account for these differences.

The distinction between shared and nonshared family influences is im-

portant to refining an understanding of how family processes affect chil-

dren. Most importantly, it emphasizes that parental practices and family

events are unlikely to have uniform effects on offspring because of how

children experience, understand, and respond in individualized ways. But

the distinction between shared and nonshared influences does not radically

change current views of the importance of parental influences in the context

of genetic individuality (see Box 2-1). Moreover, until findings about the

nature of shared and nonshared family influences are based on observa-

tional and experimental studies, strong conclusions from developmental

behavioral genetics research about how parents influence their children in

shared or nonshared ways must remain tentative. Furthermore, current

research indicates that it is extremely difficult to identify objective features

of the environment that are “shared” or “nonshared” between siblings, and

that shared and nonshared effects may depend, in part, on the hereditary

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RETHINKING NATURE AND NURTURE 49

BOX 2-1

Understanding—and Misunderstanding—Parenting Influences

Most parents are concerned about doing the right things for their chil-

dren. In recent years, however, they have had reason to question wheth-

er what they do really matters. In public (Harris, 1998) and scholarly fo-

rums (Rowe, 1994; Scarr, 1992), some developmental scientists have

called into question whether parenting influences are as significant in the

lives of children as commonly believed.

Most of the reason for questioning the impact of parenting comes from

developmental behavioral genetics research. Studies emphasizing the

importance of nonshared family influences suggest that it is not how par-

ents treat offspring similarly that matters (such as their childrearing style,

parental income or education, or socioeconomic status); it is their differ-

ential treatment of siblings that is developmentally influential. This is con-

trary to how most parents understand their influence on offspring. More-

over, behavioral genetics researchers observe that traditional studies of

parenting confound the influence of heredity with the influence of chil-

drearing practices. Children become interested in reading, for example,

not only because of a home environment in which parents model reading,

but also because of shared genes related to intelligence, activity level,

and other characteristics that underlie reading interest and ability. From

this view, therefore, parents’ most significant contributions to the devel-

opment of children are the genes they contribute, not the home environ-

ment they create.

Clearly, parents respond to the genetically driven characteristics of

their offspring (a phenomenon called a “gene-environment correlation”).

Indeed, doing so is a characteristic of good parenting. Adults should treat

their offspring differently because of their unique personalities, age, sex,

and other characteristics. But gene-environment correlation typically ac-

counts for only a small part of the variability in children’s characteristics,

and parental behavior remains a large independent influence on offspring

(Plomin et al., 1997b; Rutter et al., 1999a; see, e.g., Ge et al., 1996). The

importance of parenting is further underscored by experimental studies

that directly modify parental practices to create changes in the behavior

of children that cannot be explained by the hereditary characteristics of

offspring (Baumrind, 1993; see, e.g., van den Boom, 1994). This means

that when parenting changes significantly (independently of gene-envi-

ronment correlation), the behavior of children adjusts accordingly.

In the end, research shows that parenting does matter to children’s

development (Collins et al., 2000; Maccoby, 1999). At the same time,

developmental scientists are increasingly recognizing the need to consid-

er the influence of a child’s heredity characteristics as moderators of pa-

rental influence, and to incorporate into their research designs attention

to hereditary influences. As a result, a new generation of parenting re-

search is emerging that more thoughtfully illustrates the developmental

integration of nature and nurture in the family environment.

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50 FROM NEURONS TO NEIGHBORHOODS

characteristics of the child (Rutter, in press; Rutter et al., in press;

Turkheimer and Waldron, 2000). This form of gene-environment interac-

tion is discussed in the next section.

Like the focus on the heritability estimate, a strong emphasis on the

relative influence of shared and nonshared family influences risks missing

the important conclusion of developmental behavioral genetics research:

specifically, that the action is in the interaction between heredity and envi-

ronment. The manner in which the family environment accommodates to

and modifies a child’s heritable characteristics shapes the development of

those characteristics in a family environment that is also evolving over time.

MOLECULAR GENETICS

Developmental behavioral genetics examines nature and nurture indi-

rectly through the behavioral characteristics of genetically related and unre-

lated individuals. But it would be far more informative if researchers could

identify specific, individual genes associated with distinctive human charac-

teristics, examining their behavioral consequences in concert with particu-

lar environmental influences. That goal is slowly being realized because of

advances in molecular genetics, a relatively new science that is based on

significant technological advances in mapping the human genome and con-

ceptual advances in studying the connections between genes and behavior.

Molecular genetics begins with the scientifically complex task of iden-

tifying DNA markers for specific genes and connecting genes and behavior

through relative linkage studies and association strategies (for overviews of

these procedures, consult Plomin et al., 1997a; Plomin and Rutter, 1998;

Rutter et al., 1999a). There have been significant advances in molecular

genetics during the past decade owing to advances in mapping the human

genome and the development of less intrusive and expensive technologies

for extracting and genotyping DNA from human biological samples. There

is every reason for confidence that further advances in genetic mapping and

in linkage and association studies will soon provide a strong foundation for

the integration of molecular genetics into the behavioral research of psy-

chologists.

For developmental psychologists of the future, therefore, molecular

genetics offers the remarkable possibility of identifying the genetic markers

associated with specific behavioral propensities in children and examining

the manifestations of these propensities in relation to environmental fac-

tors, developmental changes, and the influence of other genes. Molecular

genetics will also enable researchers to develop more powerful analytic

methods and theoretical models for understanding the influence of heredity

on behavioral development. Perhaps most important,

molecular genetics

will help developmental psychopathologists understand the genetic bases

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RETHINKING NATURE AND NURTURE 51

for childhood disorders, which will include a better appreciation of the

continuities between typical variability in personality functioning and atypi-

cal deviation, improved detection of continuities in psychopathological risk

across developmental transitions, and the potential of reconceptualizing

clinical syndromes according to their genetic bases (Plomin and Rutter,

1998). There have already been promising discoveries, such as advances

toward the identification of a susceptibility gene for autism and autistic-like

characteristics, and research findings suggesting inherited propensities to

attention deficit hyperactivity disorder through genes regulating neurotrans-

mitter receptors (Rutter et al., 1999b). Furthermore, impending discoveries

from molecular genetics studies will provide added evidence that: (a) he-

reditary influences are polygenic and multifactorial, involving the impact of

multiple genes coacting with environmental influences to increase the like-

lihood of certain behavioral propensities; (b) genetic bases for developmen-

tal disorders reflect, in most cases, extreme variations on a continuum that

includes normal variants of the same characteristics; and (c) genetic effects

on behavior are probabilistic (rather than predetermined) because they

increase the likelihood that certain characteristics will occur, but do not

directly cause them (Plomin and Rutter, 1998).

Consistent with the more complex portrayal of nature and nurture

emerging from molecular genetics is a new appreciation of the importance

of gene-environment interaction. Gene-environment interaction indicates

that genetic susceptibility may increase an individual’s sensitivity to specific

environmental influences. Such an interaction is especially important in

understanding hereditary vulnerability to environmental stresses that might

lead to psychopathology. Gene-environment interaction is demonstrated

when researchers find, for example, that there is small to moderate risk for

antisocial behavior in individuals who have either a genetic susceptibility

for this disorder or grow up in a stressful environment, but for individuals

with both genetic and environmental risk for antisocial behavior, the prob-

ability of pathology is sharply higher (Cadoret et al., 1995a, 1995b, 1996;

Rutter et al., 1999b).

Comparative studies with animals can specify these gene-environment

interactions more precisely. In one investigation, for example, rhesus mon-

keys with a specific genetic vulnerability affecting neuroendocrine function-

ing who grew up under adverse (peer-rearing) conditions consumed more

alcohol in experimental conditions (Campbell et al., 1986a) than did mon-

keys without this vulnerability. However, monkeys raised under advanta-

geous (mother-reared) conditions with the same genetic vulnerability con-

sumed less alcohol than those without it, suggesting that a genetic risk

factor under adversity was a protective factor in advantaged conditions.

Other forms of gene-environment interaction were apparent with respect to

dominance-related assertive behavior in this sample, showing that positive

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52 FROM NEURONS TO NEIGHBORHOODS

early rearing significantly buffered the detrimental social impact of specific

genetic vulnerability in young rhesus monkeys (Bennett et al., 1998; Suomi,

2000). These studies underscore how significantly developmental outcomes

depend on the interaction of heredity and environment, rather than the

direct effects of either. They also indicate how the behavioral effects of

genetic vulnerability can be altered in the context of positive or negative

early rearing.

As this research shows, the identification of gene-environment interac-

tion is important not only to understanding developmental psychopathol-

ogy but also to its prevention, since it indicates how individuals with a

genetic propensity to the development of a disorder may be buffered from

its emergence if their environments are made more protective. A child with

an inherited vulnerability to antisocial personality is much less likely to

develop this disorder in supportive, nonstressful family, school, and com-

munity environments.

Typical research designs in developmental behavioral genetics lack

power to detect these interactions and, in fact, they are often not measured

at all (Lemery and Goldsmith, 1999), but molecular genetics research has

the potential for identifying gene-environment interactions, as the suscep-

tibility genes to personality characteristics become identified. Behavioral

studies suggest the existence of many such gene-environment interactions,

such as the heightened responsiveness of temperamentally fearful, inhib-

ited young children to maternal discipline efforts (Kochanska, 1993, 1995,

1997), the stronger impact of mother-infant synchrony on the growth of

self-control of temperamentally difficult children (Feldman et al., 1999),

and other illustrations of what Belsky (1997) describes as children’s differ-

ential susceptibility to rearing influences. As the field of molecular genet-

ics matures, in other words, it will become possible to understand how the

hereditary characteristics of children influence their responsiveness to pa-

rental incentives, their susceptibility to environmental stresses and de-

mands, and their vulnerability (in concert with environmental risk) to

psychopathology.

Psychology is thus at the dawn of a new era. Not only will molecular

genetics enable scientists in the near future to better understand how the

interaction of multiple genes influences behavioral characteristics, but it

will also illuminate how gene action can augment vulnerability or resistance

to environmental demands. This view of the multifactorial origins of be-

havior, reflected especially in gene-environment interaction, is another re-

flection of the essential integration of nature and nurture in behavioral

development.

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RETHINKING NATURE AND NURTURE 53

BRAIN DEVELOPMENT

Brain development also reflects the coaction of nature and nurture. The

traditional view of early brain development describes a process under tight

genetic control, and to a great extent this portrayal is true. Important

regulatory genes, such as the “homeobox” genes discovered in the fruit fly,

control the timing of the expression of other genes and can direct the

development of an entire segment of the insect’s anatomy, such as an eye or

a limb. Comparable genes have been shown to exist in mammals, including

humans, which play similarly significant developmental roles. There is no

question that there are genetically driven developmental processes that guide

the basic organization of the body and the brain, and these processes influ-

ence the growth of single cells and entire systems.

But as the opening paragraphs of this chapter illustrate, gene expres-

sion always occurs within the context of the intracellular and extracellular

environments within the body, and in the context of experience in the

outside environment. These multilevel environmental influences are neces-

sary to coordinate the complex behavioral and developmental processes

that are influenced by heredity, as well as to provide catalysts to gene

expression that enable behavior to become fine-tuned to the external set-

tings in which the organism lives. When songbirds first hear their species’

song, or when patterned

light first hits the retina of the human eye, these

experiences provoke a cascade of gene expression that commits neural

development to certain growth patterns rather than others. This is because

the genetically guided processes of neural development are designed to

capture experience and to incorporate the effects of experience into the

developing architecture of the nervous system. This is especially true of

human brain development.

The purpose of a brain is to store, use, and create information. The

amount, complexity, and contingency of the information required for hu-

mans is far greater than that of the fruit fly, and this is one reason why the

strong regulatory influence of homeobox genes in the fruit fly provides a

poor model for human brain development. A limited amount of informa-

tion is required to enable a fruit fly to function successfully for a short life

span, and much of the necessary information can be encoded genetically.

By contrast, humans acquire information primarily from experience, in-

cluding their systems for thinking, feeling, and communicating. Most of

human knowledge cannot be anticipated in a species-typical genome (e.g.,

variations in culture, language, and technology), and thus brain develop-

ment depends on genetically based avenues for incorporating experience

into the developing brain. This developmental integration of nature and

nurture enables humans to grow and adapt as a species in a manner un-

equalled by any other (fruit flies don’t have books, movies, radio, or televi-

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54 FROM NEURONS TO NEIGHBORHOODS

sion from which to learn, and the only webs available to them are danger-

ous ones), permitting unparalleled flexibility in behavior and development.

The incorporation of experience into the genetically driven plan for human

brain development helps to account for many of the unique qualities of the

species.

Developmental neurobiologists have begun to understand how experi-

ence becomes integrated into the developing architecture of the human

brain (see Chapter 8 for further details). First, developmental processes of

brain growth are based on the expectation that certain experiences will

occur that will organize and structure essential behavioral systems. These

developmental processes have been called “experience-expectant” because

normal brain growth expects and relies on these forms of environmental

exposure (Greenough and Black, 1992). Not surprisingly, the experiences

that are incorporated into normative brain development are ubiquitous in

early life: exposure to patterned light and auditory stimulation are two of

the best studied, and there are likely to be others (such as acquiring physical

coordination in gravity). Deprivation of these essential forms of environ-

mental exposure can cause life-long detriments in behavioral functioning.

Second, throughout life, new experiences also help to trigger new brain

growth and refine existing brain structures. This is, in fact, how learning,

memories, and knowledge are acquired and retained throughout the life

course. These developmental processes are called “experience-dependent”

because they rely not on species-typical environmental exposures but in-

stead on the idiosyncratic and sometimes unique life experiences that con-

tribute to individual differences in brain growth (Greenough and Black,

1992). For example, there is evidence that brain functioning is changed in

subtle ways if a person is a stringed instrument musician, which can alter

neural areas governing the finger movements of each hand (Elbert et al.,

1995). Experience-dependent brain development is thus a source of the

human brain’s special adaptability and lifelong plasticity (Nelson, 1999).

Each person has a unique history of experience-dependent influences on

brain growth.

Brain development therefore depends on an intimate integration of

nature and nurture throughout the life course. Indeed, processes of brain

development that were traditionally regarded as genetically hard-wired

(such as visual capability) have now been discovered to depend on an

exquisitely coordinated dance between experiential catalysts and the he-

reditary design for brain growth. Both nature and nurture are essential to

the development of a brain of uniquely human capacities and potential.

These developmental processes are discussed in further detail in Chapter 8.

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RETHINKING NATURE AND NURTURE 55

CONCLUSION

The integration of nature and nurture, revealed in the findings of be-

havioral genetics, molecular genetics, and brain development research,

should significantly influence how human development is understood. Con-

trary to the traditional view that heredity imposes constraints and environ-

ments induce change in developmental pathways, research in developmen-

tal psychobiology shows that nature and nurture are each sources of stability

and malleability in human growth. More importantly, their coaction pro-

vides the impetus for development, whether it is viewed from the perspec-

tive of “experience-expectant” brain growth or the interplay between of

genes and environments. The developmental action is in the interaction of

nature and nurture.

Although work in developmental psychobiology has contributed most

significantly to a revised view of hereditary influences, it also causes us to

regard the environment in a different way. Most importantly, we now

appreciate that how children respond to environmental incentives is based,

in part, on hereditary predispositions (gene-environment interaction), that

the social environment adapts itself to a child’s inherited characteristics

(O’Connor et al., 1998), and that one of the most important ways of

understanding environmental influences is how children are individually

affected (the nonshared environment). Environmental influences are not

just externally “out there”: a child’s responses to the family, the neighbor-

hood, and the culture hinge significantly on genetically based ways of feel-

ing, interpreting, and responding to environmental events. For parents and

practitioners, this underscores the importance of taking into account each

child’s individuality to create conditions of care that accord with the child’s

inherited attributes and which, for some children, provide buffers to modify

the expression of heritable vulnerabilities. Indeed, the importance of the

goodness of fit between the environment and heritable characteristics also

shows why human relationships are so profoundly important in early devel-

opment, since human partners who know a child well are the environmen-

tal influences that can most easily accommodate helpfully to a child’s indi-

viduality.

The inextricable transaction between biology and experience also con-

tributes to a better understanding of developmental disorders and the ef-

fects of early intervention. Hereditary vulnerabilities establish probabilis-

tic, not deterministic, developmental pathways that evolve in concert with

the experiential stressors, or buffers, in the family, the neighborhood, and

the school. That is why early experiences of abuse, neglect, poverty, and

family violence are of such concern. They are likely to enlist the genetic

vulnerabilities of some children into a downward spiral of progressive dys-

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56 FROM NEURONS TO NEIGHBORHOODS

function. By contrast, when children grow up in more supportive contexts,

the hereditary vulnerabilities that some children experience may never be

manifested in problematic behavior.

Understanding the coaction of nature

and nurture thus contributes to early prevention.

Early intervention, especially when it is well tailored to a child’s indi-

vidual characteristics, can be helpful in shifting the odds toward more

optimal pathways of later growth, but because the nature-nurture interac-

tion is dynamic over time, there are no guarantees. Each new developmen-

tal stage provokes new forms of gene-environment transactions that may

alter, or maintain, previous pathways. This means that giving young chil-

dren a good early start increases but does not guarantee later success, and

that children who begin life at a disadvantage are not doomed to enduring

difficulty. The interaction of nature and nurture underscores the impor-

tance of creating current conditions of care that respect inherited character-

istics, recognizing that nature-nurture is a source of continuing potential

change across the life course.

Finally, research in developmental psychobiology emphasizes the conti-

nuity that exists between typical and atypical variability in human charac-

teristics. One of the important emerging insights of molecular genetics is

that many psychological difficulties arise not from single-gene mutations,

but instead from extreme variations on a biological continuum that in-

cludes normal variants of the same characteristics. There is, in other words,

a very broad range of individual differences in which the boundaries be-

tween the normative and the atypical are matters of degree rather than

quality. This means that, in studying the growth of typical children, re-

searchers gain insight into the developmental dynamics of atypicality and

that, conversely, efforts to understand the challenges of children with devel-

opmental disorders yield insights into normative growth.

These conclusions are consistent with the broader themes of this report

and of the findings of research on early childhood development. Taken

together, they indicate that despite a long historical tradition of dissociating

the effects of nature and nurture on human character and development,

their influences are, in the end, indissociable.

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The Challenge of

Studying Culture

evolutionary advances in communications technol-

ogy and increasing globalization have resulted in un-

precedented access to the richness of human variation. In this context, as

understanding of the dynamic interaction between nature and nurture

continues to grow, the concept of culture offers a promising framework

for thinking about the full meaning of nurture in the process of human

development.

Interest in the influence of culture on child development, particularly as

it is mediated through early childrearing practices, extends across a range of

scholarly disciplines, including anthropology, sociology, philosophy, and

psychology. Building on the seminal contributions of Margaret Mead, to

Murchison’s Handbook of Child Psychology (Murchison, 1931), and

Carmichael’s Manual of Child Psychology (Carmichael, 1946), all of the

leading authoritative volumes on child development research had incorpo-

rated a cross-cultural perspective by the middle of the 20th century (e.g.,

Greenfield and Suzuki in Damon et al., 1998; Whiting in Lindzey, 1954;

Whiting and Whiting in Mussen, 1960), and specialized volumes on infancy

began to appear (e.g., Mead and Macgregor, 1951; Whiting and Child,

1953).

Notwithstanding this early establishment of a firm cross-cultural foun-

dation for the science of early childhood development, the explosion of

cognitive psychology in the 1960s paid relatively little attention to the

effects of environmental influences on the emerging competencies of young

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58 FROM NEURONS TO NEIGHBORHOODS

children. Dominated by the revolutionary thinking of Jean Piaget (1952)

and Noam Chomsky (1965), this new generation of psychologists cel-

ebrated the role of young children as active agents in their own develop-

ment and attributed early skill acquisition to the universal emergence of

innate cognitive and linguistic structures that required relatively modest

environmental guidance.

In the early 1980s, following the publication of Mind in Society

(Vygotsky, 1978) and The Ecology of Human Development (Bronfen-

brenner, 1979), the pendulum swung back toward a greater appreciation of

the extent to which all human development unfolds within a wide variety of

cultural contexts. In his analysis of the child development research litera-

ture based largely on the findings of highly controlled laboratory experi-

ments, Bronfenbrenner (1979:19) underscored the limitations of most em-

pirically based developmental psychology, characterizing it as “the science

of the strange behavior of children in strange situations with strange adults

for the briefest possible periods of time.” Subsequently, in contrast to

Piaget’s image of the young child as a solitary scientist, a growing subgroup

of child development researchers returned to the concept of human devel-

opment as a socially embedded phenomenon, thereby emphasizing the im-

portance of culture (e.g., Rogoff and Chavajay, 1995).

Building on this evolving framework, the committee began its work

with a strong conviction about the importance of culture as a highly salient

influence on early childhood development. As our examination of the

knowledge base progressed, we became increasingly appreciative of its com-

plexity. In part, this complexity is related to the multidisciplinary nature of

the field and its reliance on a wide array of qualitative and quantitative

methods. Beyond methodological diversity, however, the committee was

struck by the extent to which much of the research on the role of culture in

child development is tied to values and personal beliefs.

Thus, the task of assessing the science of culture was exceedingly more

complicated than assessing the neurobiology of brain development. This

complexity was particularly apparent when the committee attempted to

define and disentangle the concepts of culture, ethnicity, and race, and to

seek greater understanding of the effects of racism, discrimination, and

minority status on the development of young children. Consequently, this

report presents a more bounded analysis of culture than it does of neuro-

science. It is important that this discrepancy not be interpreted as an

indication of the relative importance of these two domains of study. Quite

the contrary, it should be viewed as a strong message both about the

significant challenges that face those who investigate the role of culture in

early childhood development and the critical need for ongoing method-

ologically rigorous research in this area.

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THE CHALLENGE OF STUDYING CULTURE 59

THE SPECIAL CONTEXT OF THE

EARLY CHILDHOOD PERIOD

Most definitions of culture have focused on the intergenerational trans-

mission of various combinations of symbolic (e.g., ideas, beliefs, and val-

ues) and behavioral (e.g., rituals and practices) inheritances (Shweder et al.,

1998). In the realm of early childhood development, symbolic inheritances

include (but are not limited to) parents’ expectations, goals, and aspirations

for their children; the values that govern differential approaches to disci-

pline; gender roles; religious or spiritual values; and ideas and beliefs about

health, illness, and disability. Behavioral inheritances, in turn, are embod-

ied in the “scripts” that characterize everyday routines for such common

activities as sleeping, feeding,

and playing, among others, and the distinc-

tive contexts that shape cognitive, linguistic, and social-emotional develop-

ment and thereby influence the acquisition of specific skills or behaviors.

Some observers have directed their attention preferentially to values and

beliefs. Others have focused primarily on behaviors and practices. Shweder

et al. (1998) emphasize the importance of integrating both—“the beliefs

and doctrines that make it possible for a people to rationalize and make

sense of the life they lead” and “patterns of behavior that are learned and

passed on from generation to generation” (p. 867).

One of the most extensively studied examples of contrasting develop-

mental values is the difference between cultures that promote individualism

(found predominantly in European and European-American societies) and

those that favor interdependence (reflected most prominently in Asian,

African, and Latin American societies) (Greenfield, 1994; Greenfield and

Suzuki, 1998; Markus and Kitayama, 1991; Triandis, 1988). Although all

cultures must find a balance between individual autonomy and shared

interests, there is considerable variation in each society’s location along the

continuum. Those that place greater emphasis on the former socialize their

children in a way that promotes a greater sense of independence and a

strong orientation toward individual achievement and self-fulfillment.

Those that favor the latter socialize their children to focus on the impor-

tance of their responsibilities to others and the value of viewing personal

achievements in terms of their contribution to collective goals. Neither

orientation is intrinsically more adaptive or more “normal” than the other.

Each reflects the desire for a certain kind of society, with both benefits and

costs. When greater emphasis is placed on interdependence, there is a

stronger sense of connectedness, sharing, and solidarity, but there may be a

real cost in the form of suppression of individual development. When

greater autonomy and self-reliance are promoted, there is often a consider-

able level of material productivity and individual liberty, but there may be

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60 FROM NEURONS TO NEIGHBORHOODS

a serious cost in the form of strained relationships and social alienation

(Kim, 1987).

Central to the process of intergenerational culture transmission during

the early childhood years is the translation of cultural belief systems (“pa-

rental ethnotheories”) into parenting practices (Goodnow and Collins,

1990; Harkness and Super, 1992; Sigel et al., 1992). Whiting and Child

(1953) noted both similarities and differences in approaches to childrearing

in different cultures, and identified distinctive parenting practices as impor-

tant reasons for the variations in child outcomes found across diverse popu-

lations. LeVine (1977:20) proposed a hierarchy of three universal goals

that all parents have for their children: (1) physical survival and health, (2)

development of the capacity for economic self-maintenance, and (3) devel-

opment of the “behavioral capacities for maximizing other cultural val-

ues—e.g., morality, prestige, wealth, religious piety, intellectual achieve-

ment, personal satisfaction, self-realization—as formulated and symbolically

elaborated in culturally distinctive beliefs, norms, and ideologies.” In a

society in which threats to physical survival are significant, caregiving is

focused primarily on protection. When survival is assumed, childrearing

practices reveal a process of socialization that reflects the values of the

culture and the aspirations of parents for their children.

Miller and Goodnow (1995) defined cultural practices as “actions that

are repeated, shared with others in a social group, and invested with nor-

mative expectations and with meanings or significances that go beyond the

immediate goals of the action” (p. 7). They further noted their appeal as “a

construct that will both contextualize development and provide a way of

bringing together what are often described under the separate labels of

thinking, doing, feeling, and becoming” (p. 7). Thus, according to Miller

and Goodnow, their value for child development researchers is reflected in

the way cultural practices: (1) provide a vehicle for studying development-

in-context, without separating child and context and without separating

development into a variety of separate domains; (2) reflect a particular

social and moral order; (3) serve as a route by which children come to

participate in a culture, allowing the culture to be reproduced or trans-

formed within each child; (4) have a history and a relation to both support-

ing and competing practices; and (5) have consequences based on the na-

ture of participation in a given practice.

One of the most extensively studied cultural practices in early child-

hood is the routine sleeping arrangements that are made for babies and

young children (see Chapter 5). In the United States, where autonomy and

independence are highly valued traits, most children sleep alone in a sepa-

rate room away from their parents (Abbott, 1992; Lozoff et al., 1984;

Morelli et al., 1992). In most of Asia, Africa, and Latin America, where

interdependence and solidarity are preferred, children routinely sleep with

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THE CHALLENGE OF STUDYING CULTURE 61

one or more of their parents or siblings, even when separate rooms are

available (Caudill and Plath, 1966; Konner and Worthman, 1980; Shweder

et al., 1995). In two-thirds of the cultures surveyed in one international

study, mothers routinely slept in the same bed with their infants, and the

percentage was even higher when sleeping in the same room was included

(Barry and Paxon, 1971; Burton and Whiting, 1961). This pattern was

found not only in developing nations, but also in highly industrialized

societies such as Japan, where children typically sleep with their parents

until age 5 or 6 years (Caudill and Plath, 1966).

Despite the relatively unusual nature of typical U.S. sleeping practices

compared with the rest of the world, there is also considerable subgroup

variability within the country. In a Cleveland, Ohio, study, only 3 percent

of babies in white, urban, middle-class, two-parent families slept in their

parents’ bedroom under one year of age, and only 1 percent did so in the

second year. In contrast, parent-child cosleeping was reported for black

children in the same urban area at a rate of 55 percent for children in the

first year and 25 percent between 1 and 5 years of age (Litt, 1981). A

subsequent study in a predominantly white, blue-collar community in Ap-

palachian Kentucky found cosleeping among 71 percent of children be-

tween 2 months and 2 years of age, and 47 percent between 2 and 4 years

(Abbott, 1992). Lozoff et al. (1984) found that babies in white, middle-

class families are more likely to sleep with their parents when they are ill,

when the family moves, or when there is marital conflict.

Both cosleeping with a parent or sleeping alone appear to be adaptive

in a variety of cultural contexts. For example, !Kung children have been

observed to be more independent than their counterparts in the United

States, notwithstanding their early cosleeping experiences (Klein, 1995;

Konner, 1982). It is of interest to note, however, that parental concerns

about sleep problems in young children are common in the United States,

less frequent in Japan (Nugent, 1994), and nonexistent in Kenya (Super and

Harkness, 1982). It is not clear whether these differences reflect parent

perceptions or actual sleep disturbances. Moreover, although the Japanese

mother-child relationship remains relatively

strong into adulthood, the hus-

band-wife bond is typically less close than in the United States (Lebra,

1994). In short, cultural differences in early childhood sleeping arrange-

ments are neither better nor worse; they simply reflect contrasting prefer-

ences and differential trade-offs.

Differences in early caregiver-child interaction patterns and communi-

cation styles further illustrate alternative childrearing strategies, as well as

the futility of searching for universally normative or optimal practices.

Mothers of Gusii toddlers in Africa and Zinacantecan toddlers in Central

America, who use a great deal of imperatives when they speak to their

offspring, generally have children who grow up to be relatively obedient

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62 FROM NEURONS TO NEIGHBORHOODS

and nonquestioning (Greenfield et al., 1989; LeVine et al., 1994). Toddlers

in the United States, whose mothers typically speak with them using inter-

rogatives, often grow up to be more questioning and self-assertive (LeVine

et al., 1994). Americans would judge Gusii parents as excessively authori-

tarian and punitive, and their toddlers as passive. The Gusii would view

American parents as overindulgent, and their toddlers as undisciplined

(LeVine et al., 1994). In a study of mother-infant dyads playing with toys,

Fernald and Morikawa (1993) observed that American mothers tended to

name the objects, in contrast to Japanese mothers, who produced soft,

easily imitated sounds and encouraged positive feeling toward the toys.

Greenfield and Suzuki (1998) characterized these differences as a behav-

ioral manifestation of the American value preference for cognitive stimula-

tion (i.e., “technological intelligence”) versus the greater Japanese interest

in interpersonal relationships (i.e., “social intelligence”).

The take-home message from this evolving literature is clear. Cultural

practices related to early childrearing are highly variable and lead to differ-

ent developmental outcomes. Many of those who embrace a particular

practice typically do so because they believe in its relative superiority, al-

though there is generally scant evidence to support the conclusion that one

practice is inherently better than others. Yet this message does not mean

that any and all beliefs and practices are equivalent in the extent to which

they promote the health and development of young children. Some differ-

ences are trivial, some are matters of preference or style, and some have

important consequences that may be particularly helpful or destructive to

individuals or to society. Indeed, some practices can pose significant threats

to children’s physical or emotional well-being (e.g., binding the feet of

young girls, using severe physical punishment to enforce obedience to au-

thority, or imposing highly restricted diets that result in malnutrition).

Ethnocentric arrogance leads to the firm belief that one’s way is “the only

right way.” Sound scientific thinking asks how and why cultural practices

differ and assesses their differential developmental consequences, in both

the short and long term. It is therefore essential that the full range

of possible effects of contrasting childrearing practices be evaluated

objectively.

CULTURAL DIVERSITY IN THE UNITED STATES

Although much can be (and has been) learned about the relation be-

tween culture and child development from cross-national studies, there is

also much to be learned from the rich diversity of childrearing beliefs and

practices exhibited by families in the United States. A great deal of that

variability can be found in that part of the population whose ancestors

emigrated from Europe. Significantly more resides among those whose

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THE CHALLENGE OF STUDYING CULTURE 63

ancestral origins can be traced to various countries in Africa, Latin America,

and Asia and who continue to be self-identified or socially identified with

those origins. In fact, except for the contributions of the Native American

population, most aspects of mainstream culture in the United States have

been transported from another society. As such, American culture is modi-

fied and reshaped by each newly arrived group, as well as by each succes-

sive generation. In this respect, like most open societies in the world today,

the United States is a nation whose culture remains a continuous work in

progress.

The complex amalgam of cultures that encompass the contemporary

U.S. population includes the contributions of a variety of groups whose

initial arrival reflected a mixture of circ*mstances, including voluntary

immigrants, involuntary slaves, grateful refugees, and conquered indigenous

peoples. Some communities reflect more than two centuries of accultura-

tion since the original departure from their homeland; others can measure

their date of arrival in months. Some experience a sense of genuine wel-

come; others bear the burdens of hostility and overt discrimination. Some

blend more easily into the mainstream; others feel more isolated at its

fringes. Within this multilayered context, research on the role of culture in

the development of young children in the United States is exceedingly com-

plex and challenging.

Central to greater understanding is the need to identify the diverse and

frequently overlapping elements of ethnicity, which include national origin,

race, minority status, language, and religion. Ethnicity can be an amalgam

of any or all of these, and the task of defining it is not an easy one. Helms

(1990:293) defined ethnicity as “a social identity based on the culture of

one’s ancestors’ national or tribal groups and modified by the demands of

the larger culture or society in which one currently resides.” Entwisle and

Astone (1994) proposed ethnic categories for research purposes based on

race and place of origin. García Coll and Magnuson (2000) described

ethnicity as a group status defined by a common nationality, culture, or

language. Phinney (1996) noted that the boundaries of ethnicity are blurred

and flexible, and that its implications vary widely across individuals. Con-

sequently, she suggested that it be treated not as a categorical variable but

as a dynamic aspect of human experience (Goodchilds, 1991). Three di-

mensions of difference that vary within and across groups, as well as within

individuals over time, are suggested for examination—ethnicity as culture,

ethnicity as identity, and ethnicity as minority status (Phinney, 1996).

Equating ethnic status with distinctive cultural characteristics is highly

problematic. Central to the problem is the common finding of significant

variation within ethnic groups in values, beliefs, and practices—variations

that can often exceed the magnitude of differences between groups. Most

attempts to describe the culture of different ethnic groups in the United

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64 FROM NEURONS TO NEIGHBORHOODS

States typically begin with the general characteristics of their native region

(e.g., Asia, Africa, Europe, Latin America). This is usually followed by the

identification of distinguishing features related to their specific country of

origin, the generation and timing of immigration, the region of settlement

in the United States, religious affiliation and practice, current community

structure, and current socioeconomic status. Different members of a given

ethnic group generally demonstrate varying degrees of adherence to its

identifiable values, beliefs, and practices, thereby making it virtually impos-

sible to characterize “the culture”

of the group.

Individuals can claim ethnicity as an identity, independent of the extent

of one’s adherence to its cultural values and practices, which has been

characterized as “symbolic ethnicity” or “ethnic loyalty” (Keefe, 1992;

Keefe and Padilla, 1987). Embedded in this construct is a sense of member-

ship in an ethnic group and a positive feeling about the affiliation (Bernal

and Knight, 1993; Phinney, 1990, 1996). Like culture, ethnic identity is a

complex phenomenon that varies among the members of a group, as well as

in individuals over time. Its psychological correlates also vary, depending

on the quality of the identity (Phinney, 1996) and whether it is the result of

self-labeling or labeling by others.

Some ethnic groups are characterized as minority groups. This charac-

terization implies a position of relative disadvantage with respect to power

and status, often accompanied by previous or ongoing experience with

racism or other forms of prejudice and discrimination (Phinney, 1996). It

too varies among individuals and over time. In selected cases, it may be

correlated with any of a variety of historical experiences that differentiate

specific groups, such as slavery, internment, relocation, and refugee or

immigrant status.

The concept of race can be especially difficult to define. García Coll

and Magnuson (2000) defined race as a term used in the United States to

describe a group of people who are defined mainly by physical characteris-

tics, such as skin color, hair type, and other features. In reality, a significant

proportion of the U.S. population is of mixed racial descent, and many

individuals only marginally resemble the physical prototype of a distinctive

race.

Although preschool children do not have well-formulated ideas about

race, it is among their earliest emerging social categories. By the time they

are 4 years old, children appear to realize that race is an enduring feature

that is inherited from parents and established at birth. They also seem to be

aware that race is a dimension along which humans are arranged hierarchi-

cally, but they do not have a very clear idea about who belongs to which

category. Unlike gender, race is not a particularly salient or important

dimension by which preschoolers spontaneously categorize people, espe-

cially when it comes to choosing playmates. The translation of racial

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THE CHALLENGE OF STUDYING CULTURE 65

categories into racially based behavior appears to occur after the preschool

years (Hirschfeld, 1994). The early development of perceptions and atti-

tudes about race (both one’s own and that of others) is a highly sensitive

concern in a pluralistic society. This critical issue, which was not addressed

by the committee, demands extensive, multidisciplinary investigation.

DEMOGRAPHIC CHALLENGES AND OPPORTUNITIES

Notwithstanding the absence of clear definitions of race and ethnicity,

they persist as prominent demographic markers for categorizing children

and families, even as the blending of cultures increases and the racial and

ethnic diversity of the U.S. population grows. Over the past two decades,

the proportions of Asian and Hispanic children in the United States have

increased while the young black population has remained stable and the

percentage of whites has declined. Much of this growing diversity of young

children is the result of increased immigration and higher birth rates among

immigrants and their descendants, who represent more than 100 different

ethnic and linguistic groups (National Research Council and Institute of

Medicine, 1998a). These trends are projected to continue, if not accelerate,

through the early decades of the 21st century, such that current notions of

majority and minority groups will become less meaningful for children and,

as they age, for adults as well.

By the year 2030, children in families of European origin will make up

less than 50 percent of the population under age 5 (National Research

Council and Institute of Medicine, 1998a). These demographic realities

suggest both promising opportunities and potentially sobering challenges.

The opportunities offered by a multicultural society that is cohesive and

inclusive are virtually limitless—including the richness that comes from a

broad diversity of skills and talents, and the vitality that is fueled by a range

of interests and perspectives. The challenges posed by a multicultural

society that is fragmented and exclusive are daunting—including the wasted

human capital that is undermined by prejudice and discrimination, and the

threat of civil disorder precipitated by bigotry and hatred.

The changing demographics of the early childhood population in the

United States present both the opportunity and the challenge of a great

social experiment. The outcome of this experiment will be influenced to a

large extent by how human diversity is addressed in the rearing of children.

The foundations of relationships and the fundamentals of socialization are

culturally embedded and established during the early childhood years (see

Chapter 9). Consequently, further research on how young children learn

about and develop attitudes toward human differences will help to eluci-

date both the roots of categorical discrimination and the origins of social

inclusion.

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66 FROM NEURONS TO NEIGHBORHOODS

CULTURALLY COMPETENT POLICIES

AND SERVICE DELIVERY

As the population of young children in the United States becomes

increasingly diverse, policy makers and service providers face the complex

task of tailoring their efforts to build on the strengths and address the needs

of a wide variety of constituencies. Central to this challenge is a recognition

that significant cultural distance between providers and recipients of health

and human services can make it difficult to build and sustain the kinds of

relationships that often determine the short-term acceptability and ultimate

success of an early childhood intervention or family support program. In

an effort to respond to these new and growing challenges, the concept of

“cultural competence” has been formulated to guide and evaluate profes-

sional performance in a broad range of service settings. Despite its intuitive

appeal and theoretical validity, however, this concept has not been investi-

gated empirically.

Multiple terms have been used to address the need for responsiveness to

diversity, including “cultural sensitivity,” “cultural relevance,” and “cul-

tural awareness,” among others. Unlike these alternatives, cultural compe-

tence has been popularized as a knowledge base and set of skills that go

beyond the realm of simple respect and sensitivity. A culturally competent

professional is defined as one who is able to facilitate mutually rewarding

interactions and meaningful relationships in the delivery of effective ser-

vices for children and families whose cultural heritage differs from his or

her own (American Medical Association, 1994; Roberts, 1989). Notwith-

standing its current salience in the domains of policy and practice, however,

there is little scientific evidence to support this definition.

Beyond the level of individual practice, notions of cultural competence

have also been applied to systems and programs that deliver responsive

and accessible services to culturally diverse populations. Once again, al-

though the following characteristics have not been evaluated systemati-

cally, a culturally competent service system: (1) monitors assessment pro-

cedures and evaluation instruments to assure their appropriateness and

validity for the children and families who will be assessed; (2) identifies

groups that are underserved

and eliminates cultural barriers that interfere

with service provision; (3) facilitates policy planning, staff training, and

community participation in order to ensure the development, delivery, and

maintenance of culturally competent services; (4) defines the location, size,

characteristics, resources, needs, and ethnography of culturally diverse

populations within its service area; (5) builds cross-cultural communica-

tion skills; and (6) helps a broad diversity of communities organize them-

selves to enhance the availability and utilization of needed services. In a

culturally competent system of care, the family, as defined by the cultural

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THE CHALLENGE OF STUDYING CULTURE 67

perspective of the target population(s), becomes the principal vehicle for

support and the preferred agent of intervention (Coates and Vietze, 1996).

In a health care setting, cultural competence is demonstrated further by the

inclusion of cultural considerations in history taking and the formulation

of differential diagnoses, and by adapting communication patterns in

response to different cultural beliefs, practices, or traditional roles

(Oosterwal, 1994). This framework can be used successfully for bicultural

as well as multicultural families.

Isaacs and Benjamin (1991) suggested five additional traits that mark a

culturally competent service system or institution: (1) the ability to express

an appreciation for diversity; (2) the capacity for cultural self-assessment;

(3) awareness of the dynamics that occur when cultures interact; (4) the

availability of institutionalized cultural knowledge; and (5) availability of

adaptive practices, such as the appropriate use of interpreters and sensitiv-

ity to cultural celebrations. Proposed guidelines for implementing such

practices are available from a variety of sources (Bernard, 1991; Cross et

al., 1989; Isaacs, 1986; Isaacs and Benjamin, 1991; Mason, 1989; Orlandi,

1992; Rider and Mason, 1990; Roberts, 1989).

The true sign of a culturally competent system of service delivery is its

capacity to recognize the fine line between sensitivity to group differences

and the danger of stereotypic or paternalistic approaches in the service of

greater individualization. To this end, the ultimate goal should not be a

society that develops different policies for different ethnic or racial groups,

but a society that takes a families’ cultural values and practices into ac-

count when it acts on their behalf. At the present time, this perspective is

shaped by values and personal beliefs. The underlying science remains to

be developed.

EVOLVING PERSPECTIVES ON THE STUDY OF

CULTURE AND DEVELOPMENT

One of the fundamental choices facing those who study the complex

relation between culture and child development is the need to find an

appropriate balance between the identification of universals and the task of

cataloging its variations (co*cking, 1994). As noted by Kessen (1991), “No

psychologist can ignore the eternal tension between the Search for Uniform

Being, on one hand, and the Celebration of Diversity, on the other” (p.

188). Early pioneers in cross-cultural psychology identified and described

differences among societies. Investigators at the cutting edge of contempo-

rary cultural psychology recognize that culture can be studied within a

single group, and seek greater understanding of the dynamic interaction

between individuals and their contexts in a diverse array of settings

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68 FROM NEURONS TO NEIGHBORHOODS

(Greenfield, 1997; Jahoda and Krewer, 1997; Miller, 1997; Poortinga,

1997).

Among the most important tensions that arise in the study of cultural

diversity is the struggle between those who view differences as advantages

or deficits versus those who adopt a more “situated” and less ethnocentric

perspective on human variability (Cole and Bruner, 1971; Ogbu, 1994).

Central to the latter approach is a recognition that development is largely

adaptive in nature and therefore must be viewed within the context in

which it takes place and within which it evolves over time. That is to say,

“2-year-old skills” and “3-year-old behaviors” are best understood by tak-

ing into account the learning opportunities and expectations that are

embedded in the important social interactions in the child’s typical environ-

ment. Thus, the development of cognitive-linguistic abilities and the achieve-

ment of emotional well-being are linked to a child’s everyday experiences,

which are embedded in the cultural practices or “scripts” of his or her

family and society.

Closely related to the movement away from a focus on deficits toward

an interest in assets is the emergence of a new subfield of cross-cultural

research known as “indigenous psychology” (Berry, 1995). The defining

feature of this emerging field is the study of specific cultural traditions by

investigators whose personal background matches the cultural group that is

the subject of study.

CONCLUSIONS

Similar to the evolving understanding of the reciprocal interaction be-

tween nature and nurture, researchers who study human development and

culture are developing a greater appreciation for their interdependence as

well. That is to say, as children grow up, they are not simply passive

products of the culture in which they are reared. Quite the contrary, they

are active agents who pick and choose selectively from among the influ-

ences to which they are exposed, thereby shaping their own distinctive

cultural context over time (Miller and Goodnow, 1995). Fundamental to

this concept is the increasing recognition that cultures themselves are also

dynamic and continually modified by the people who experience them.

This phenomenon is most obvious in the acculturation of immigrant

children, as they navigate the borders between their native and adopted

cultures. It is also highly visible in any society during times of social

change, as individuals adjust their practices and scripts to the pressures of

newly prescribed values and behaviors. The significant social and eco-

nomic transformations that have affected U.S. society over the past few

decades (see Chapter 1) provide vivid examples of such powerful influences

on the lives of children and families. Increases in maternal employment and

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THE CHALLENGE OF STUDYING CULTURE 69

greater utilization of nonparental child care, for example, have dramati-

cally altered the daily life experiences of infants and toddlers by introducing

a greater variety of adult relationships and earlier exposure to organized

peer group activities, particularly with same-age playmates. The prolifera-

tion of early childhood enrichment activities and intense competition for

admission to prestigious preschool programs for children from affluent

families have increased performance demands within a relatively narrow

range of competencies at increasingly younger ages; and the considerable

amount of time that toddlers and preschoolers spend watching television

and playing with video games have transformed the nature of imagination

and play during the preschool years.

The lessons from these examples are clear. Culture is not a static

phenomenon. It is sustained, challenged, or modified over time. Culture is

also not a neutral construct. It draws much of its influence from the

conviction that its values and practices are inherently right and preferable

to those of others. In a pluralistic and rapidly changing society like the

United States, culture is a highly charged and constantly

moving target that

is difficult to investigate in an objective manner. Numerous examples of its

influence on early childhood development are included throughout this

report, but much further work remains to be done. However, unlike re-

search in the neurobiology of early childhood development, studies of the

relation between competence and culture are heavily infused with values

and personal beliefs. The extent to which both the capacity and the resolve

to learn more about this critical relation are strengthened will determine the

ability to understand the rich diversity of human cognitive, social, emo-

tional, and moral development, beginning in the earliest years of life.

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Making Causal

Connections

tudies of child development encompass an enor-

mously varied universe of research strategies drawn

from disciplines as diverse as economics and anthropology. These strate-

gies include moment-by-moment ratings of interactions between adults and

children and among peers, administration of psychological tests and ques-

tionnaires, ethnographic field work, laboratory research using standardized

protocols, and clinical observations. Researchers select these strategies to

address different goals. They may be most interested in elucidating associa-

tions among different facets of development, identifying emerging capaci-

ties of children as they develop, or describing the contexts in which children

grow up, to name several objectives that studies are designed to address. In

this chapter, we focus on studies that seek to identify causal connections

between a specific influence (e.g., mothers’ talk to children, an intervention

program) and child development (e.g., the child’s vocabulary, scores on a

test of school readiness).

The subset of studies that attempt to establish causal connections are

often critical in testing theories about the role of early experience in child

development, and they absorb much of the interest of policy makers and

practitioners. They can, however, be exceedingly difficult to implement in

practice and sometimes involve ethical problems. Currently, a great deal of

controversy surrounds the role of experimental studies in understanding the

effects of early interventions, in part as a result of the high-stakes policy

decisions regarding program funding that are often involved. In this con-

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MAKING CAUSAL CONNECTIONS 71

text, our discussion aims to clarify the logic and contributions of studies of

causality to the understanding of developmental processes and to interven-

tions aimed at affecting these processes. Something close to a consensus has

emerged within statistical science on the logic of causal inference: its defini-

tion, the conditions required for valid causal inference, and generalization

of causal inferences. Appendix B discusses the statistical issues involved in

defining and estimating causal effects. In the committee’s view, this consen-

sus has implications for all studies making causal comparisons, basic and

applied, experimental and nonexperimental. Here we sketch the essential

ideas in this emerging consensus and consider how these ideas can be

applied to improving early childhood research. This focus is not intended

to minimize the importance of other research strategies and goals. Re-

search is most appropriately viewed as a sequential process, properly start-

ing with exploratory observation, moving through correlational work aimed

at tracing associations among variables of interest, to more rigorous designs

permitting causal inference. Indeed, the richness of developmental science

derives from the field’s reliance on multiple methods of inquiry, and its

greatest insights often emerge at the convergence of diverse strands of

evidence.

We begin by considering causal inference in basic and applied develop-

mental research. Basic research attempts to uncover fundamental processes

of development and change, while applied research aims to help policy

makers and practitioners evaluate practical efforts to improve children’s

experiences and outcomes. We emphasize the importance of integrating

basic and applied research in building a strong science of early childhood

development. Insights from basic science are crucial in the design of prac-

tical programs, while the evaluation of programs can provide new evidence

essential to basic science about casual connections. We then discuss the

problem of generalizing from intervention studies to the populations of

children, to the settings and personnel, and to the historical times and social

contexts that might ultimately characterize a new program if its adoption

became more widespread. Well-designed studies can answer important

questions about the generalizability of a study result. Nevertheless, because

strong generalizations typically can emerge only from a stream of related

studies, we also discuss the importance of synthesizing evidence across

multiple studies. Finally, we consider the particularly thorny issue of causal

inference as it applies to growing children.

CAUSAL INFERENCE IN BASIC RESEARCH

The theory and evidence contained in this report are connected by

chains of causal reasoning. We consider how prenatal and neonatal envi-

ronments affect early brain development and behavior and how these early

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72 FROM NEURONS TO NEIGHBORHOODS

effects, together with the child’s early relationships, affect self-regulation,

social competence, language development, and reasoning. The conse-

quences of early experiences for later behavioral functioning, including the

ability to initiate and sustain relationships and to succeed in school and at

the workplace, are of central interest to theory and policy. This report and

developmental science more generally integrate empirical findings regard-

ing such causal propositions and evaluate alternative theoretical explana-

tions that tie these propositions together.

Despite their importance, however, causal connections are difficult to

nail down. Suppose, for example, that we are interested in how high-

quality relations between caregivers and infants affect later cognitive or

social functioning. For simplicity, we refer to the quality of such relations

as “quality of care.” Let us assume that we have taken great pains to define

and validly measure quality of care as well as the outcome of interest: a

specific aspect of cognitive or social functioning. When quality of care is

found to be associated with an enhanced outcome, we may be inclined to

think that the quality of care is the cause of this outcome. But children who

enjoy high-quality care are likely to have other advantages that may also

shape such outcomes. For example, they may benefit from favorable ge-

netic endowment, highly involved parents, or ample family incomes, all of

which may contribute to the cognitive and social outcomes of interest.

These other causal factors are called “confounding variables” or “con-

founders” for short. A confounding variable in the context of this example

is a child characteristic or feature of the child’s environment that (a) pre-

dicts who will receive high-quality care and (b) also predicts the outcome of

interest. The failure to control for confounders leads to an error called

“selection bias.”

Scientists try hard to devise research strategies that reduce or eliminate

selection bias. That is, they try to separate the effects of the main variable

of interest—in this case, quality of care—from effects of confounders.

We are deeply

indebted to the intellectual insights and support that they provided.

In June 1999 the committee convened a two-day Workshop on the

Science of Developmental Promotion and Early Childhood Intervention.

Participants included leading researchers and practitioners from the fields

of pediatric primary care and nursing, child care and early childhood edu-

cation, child welfare, mental heath, public health, early intervention for

children living in poverty, and early intervention for children with develop-

mental disabilities: Kathryn Barnard, University of Washington; Barbara

T. Bowman, Erikson Institute, Chicago; Jeanne Brooks-Gunn, Columbia

University; Mary Beth Bruder, University of Connecticut Health Center;

Mary Dozier, University of Delaware; Dale Farran, Vanderbilt University;

Veronica Feeg, George Mason University; Barbara Howard, Johns Hopkins

University School of Medicine; Jane Knitzer, Columbia University; Samuel

Meisels, University of Michigan; Craig Ramey, University of Alabama at

Birmingham; Arnold Sameroff, University of Michigan; Ruby Takanishi,

Foundation for Child Development; Deborah Klein Walker, Massachusetts

Department of Public Health; Mark Wolery, University of North Carolina

at Chapel Hill; and Hiro Yoshikawa, New York University. All of the

workshop participants, both in their prepared written comments and

through their contributions during the discussion sessions, added valuable

scientific input to the committee’s work. Two additional workshops orga-

nized by the Board on Children, Youth, and Families, one on home visiting

interventions and another on early precursors of antisocial behavior, also

contributed greatly to our work. The committee and staff are grateful to

everyone who participated in these meetings.

We also wish to acknowledge several consultants who contributed to

the committee process: Donald Hernandez, State University of New York

at Albany, who provided data and advice on the demographics of the birth

to five age group; Laurence Leonard, Purdue University, who advised us on

atypical language development; Joshua Brown, Columbia University, for

his synthesis of the literature on the developmental consequences of com-

munity violence; Kathleen Allen-Wallner, National Institute on Child Health

and Human Development, for her synthesis of research on regulation of

attention and executive function in young children; and Michael Georgieff,

University of Minnesota Hospital, who provided extensive information and

advice on the effects of prematurity on early brain development. We would

also like to thank Bonnie Keilty, a doctoral student in education and human

development at George Washington University, for her assistance with the

committee’s review of the literature on early intervention and her staff

support for the Workshop on the Science of Developmental Promotion and

Early Childhood Intervention. In addition, many generous hours of expert

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ACKNOWLEDGMENTS xi

consultation were provided by Charles A. Nelson, chair of the John D. and

Catherine T. MacArthur Foundation and James S. McDonnell Foundation

Research Network on Early Experience and Brain Development, who served

as a formal liaison to the committee.

In addition to formal workshops, a number of individuals were invited

to make presentations and participate in discussions at committee meetings.

In December 1998, H. Hill Goldsmith, University of Wisconsin at Madi-

son, Kathleen R. Merikangas, Yale University, and David Reiss, George

Washington University Medical Center, participated in a panel on the ge-

netics of early development, which informed the committee about cutting-

edge research on a range of issues in this area. In July 1999, Joseph

Campos, University of California at Berkeley, addressed the interplay of

experience and early brain development, and Robert LeVine, Harvard Uni-

versity, spoke about the promise of cross-cultural research, the symbiotic

development of individuals and societies, and the importance of integrating

knowledge and research methods from a variety of disciplines.

A number of experts assisted the committee by responding in writing to

questions about the relations among culture, early childhood development,

and early interventions. We are grateful to the following individuals for

their thoughtful comments on this issue: Catherine Cooper, University of

California at Santa Cruz; Doris Entwisle, Johns Hopkins University; An-

drew Fuligni, New York University; Harriette McAdoo, Michigan State

University; Suzanne Randolph, University of Maryland at College Park;

Diana Slaughter-Dafoe, University of Pennsylvania; Paul Spicer, University

of Colorado Health Sciences Center; Ruby Takanishi, Foundation for

Child Development; and Thomas Weisner, University of California at Los

Angeles.

We would also like to thank Thomas Cook and Ken Howard, North-

western University, for sharing their expertise in intervention methods and

for helping the committee examine research and evaluation methods in

depth.

Shortly after the initiation of the study process, the committee inter-

viewed a broad cross-section of individuals involved in early childhood

policy and service delivery (in contrast to research) to ensure that the final

report would be responsive to the issues that practitioners and local and

state government officials are dealing with every day. We are grateful to

the following people for taking the time to share their expertise: Douglas

Baird, Associated Day Care Services; Hedy Chang, California Tomorrow;

Veronica Feeg, George Mason University; Andrea Genser, Center for Ca-

reer Development in Early Care and Education, Wheelock College; Stacie

Goffin, National Association for the Education of Young Children; Dou-

glas Howard, Family Independence Agency, State of Michigan; Elizabeth

Iida, SRI International; Barbara Ferguson Kamara, Office of Early Child-

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xii ACKNOWLEDGMENTS

hood Development, District of Columbia Department of Human Services;

Andrew Kennedy, Los Angeles County Office of Education; Joan Lombardi,

Child and Family Policy Specialist, formerly with the Child Care Bureau of

the U.S. Department of Health and Human Services; Matthew Melmed,

Zero to Three: National Center for Infants, Toddlers and Families; Cheryl

Mitchell, Vermont Agency of Human Services; Karabelle Pizzigatti, Child

Welfare League of America; Calvin Sia, Hawaii Medical Association; Jolene

Smith, Santa Clara County, Social Services Agency; Valora Washington,

Unitarian Universalist Service Committee; and Barry Zuckerman, Boston

Medical Center.

We are grateful to the following people for reviewing our syntheses of

research on a variety of topics: Geraldine Dawson, University of Washing-

ton, for reviewing the section on maternal depression; Michael Georgieff,

University of Minnesota Hospital, and Sandra Jacobson, Wayne State Uni-

versity, for their careful reading and feedback on early versions of Chapter

8, The Developing Brain; Lawrence Hirschfeld, University of Michigan, for

clarifying our representation of his work on preschoolers’ conceptualization

of race; Tama Leventhal, Columbia University, for her assistance with the

literature on continuity of care and turbulence; Kenneth Rubin, University

of Maryland, Willard Hartup, University of Minnesota, and Carollee

Howes, University of California at Los Angeles, for reviewing early drafts

of Chapter 7, Making Friends and Getting Along with Peers; Delia Vazquez,

University of Michigan Medical School, and Seymour Levine, University of

California at Davis, for reviewing the section on neuropeptides; and Steven

Warren, Vanderbilt University, for reviewing a portion of Chapter 6, Com-

municating

The

surest way to eliminate selection bias is to conduct an experiment. In it, one

would randomly assign children to either high-quality or low-quality care,

carefully provide the kind of care assigned, and then, at some later point,

assess the outcome of interest. Random assignment would eliminate all

confounding variables. To be quite specific, random assignment would

ensure that the probability of assignment to high-quality or low-quality

care is utterly unaffected by any preexisting characteristic of the child.1

1Some have argued that random assignment eliminates selection bias only in large samples,

but this is not true. By ensuring that previous variables are unrelated to the probability of

assignment to each treatment condition, random assignment ensures that tests of statistical

significance accurately quantify the uncertainty about the causal question. Thus, when treat-

ment groups are compared on the outcome of interest, significance tests yield p-values that

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It is, of course, unethical to assign children to receive low-quality care.

Thus, many of the causal factors that are most important to theory are not

amenable to experimentation for ethical reasons. Prenatal substance use,

poor nutrition, and lack of early affection are three such examples of poten-

tially important causal factors whose effects on humans cannot be assessed

experimentally. Moreover, even when it might be ethically defensible to

experiment, it may be practically impossible. For example, a controversial

hypothesis is that keeping a 3-year-old at home with his or her mother is

better for the child than sending him or her to child care (even if the quality

of care is good). Since it is not known which kind of experience is superior,

one might ethically conduct an experiment. Yet it is usually impossible to

assign children at random to stay at home or attend child care; parents will

not allow it.

When experiments on humans are impossible for ethical or logistical

reasons, scientists use a variety of alternative strategies to eliminate selec-

tion bias. One is to create special circ*mstances in which human experi-

mentation becomes both ethical and feasible, for example, by using wait-

list controls.2 Another possibility is to conduct experiments on animals. A

great deal has been learned, for example, about the effects of highly stress-

ful rearing circ*mstances on infant development using randomized experi-

ments on monkeys (see Chapter 5). The key problem, of course, is that

findings from such experiments may not generalize to human populations.

In another example, pregnant women who smoke could be randomly

assigned to a smoking-cessation program to evaluate the effects of prenatal

smoking on child outcomes. Again, however, generalization may be tenu-

ous, as the special circ*mstances may not represent the contexts of greatest

interest scientifically. Those who volunteer to participate in the evaluation

and are assigned to either the experimental or control group may be differ-

ent from other mothers who smoke but do not volunteer to participate.

The results of the experiment may not generalize to those other mothers.

Moreover, not all participants will “comply”: some assigned to quit smok-

ing will smoke anyway, and some not assigned to the program will quit,

leading to a biased estimate of the effect of smoking.

convey the probability of obtaining a sample result of the type actually obtained if there were

no causal effect. In small samples, these p-values will, appropriately, tend to be larger than in

large samples, but in either case, the p-value and related confidence intervals are fair indica-

tors of uncertainty about the causal effect of interest.

2A possible scenario for experimentation arises when a large number of parents seek child

care and only a small number of places in child care centers are available. Then children can

be randomly assigned to receive child care or to be placed on a waiting list. Constructing a

wait-list control in this way can be a very effective research strategy, but any conclusions

must be restricted to the set of parents who are actively seeking care. Such parents may

provide a different kind of home care than would parents who are not interested in child care.

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The strategy that is perhaps most common for coping with selection

bias, however, abandons experimentation entirely. Now the goal is to

identify and control for the most plausible confounding variables, prefer-

ably by design or, alternatively, by clever statistical analysis, such as pro-

pensity score analysis or reliance on other statistical techniques that adjust

estimates of treatment impact for other influences related to the outcome.

To return to the quality of care example, researchers would ideally take

great care to obtain information on many aspects of a child’s experience,

including the prenatal behavior of the mother, the child’s birthweight, early

nutrition, the parents’ cognitive skill, parenting behavior, education, occu-

pation, and income level. They would also assess the child’s previous status

on the outcome variables of interest at least once (see discussion of time-

series designs below). They would then make a concerted effort to con-

struct comparison groups of treatment and control children or families that

are as similar as possible on these pretreatment variables. In addition, they

may attempt to adjust for such confounding variables ex posteriori, using

statistical adjustments when assessing the effects of quality of care.

Studies using these nonexperimental designs and analytic strategies are

extremely numerous and have yielded a wealth of evidence about the pre-

dictors of key childhood outcomes. In these nonexperimental approaches,

statistical adjustments after the fact can seldom make up for failures to

design as strong a quasi-experiment as possible, particularly if the groups

being compared are highly disparate prior to program participation. As

others have noted, “no matter how precise your measurement or how

sophisticated your analyses, you risk failure if your research is not well

planned. You can’t fix by analysis what you have bungled by design”

(Light et al., 1990). Unfortunately, even with a strong quasi-experimental

design, one can never be sure whether key confounders have been over-

looked or whether the method of adjustment has effectively removed poten-

tial selection biases.

Selection bias is not the only threat to valid causal inference. Another

is called “simultaneity bias.” Consider a study in which the quality of a

child’s relationships with his or her parents as well as the child’s behavior

are repeatedly assessed. Suppose one finds that changes in the quality of

parenting predict changes in the child’s behavior. Selection bias is not an

issue because comparisons are made within the same children. That is, the

child’s behavior when parents are providing the best care is compared with

the same child’s behavior when the parents are not doing such a good job.

The problem, however, is that the causal variable—parental care—will to

some extent be caused by previous child behavior (see Bell, 1968; Bell and

Chapman, 1986; Lytton, 1990; Rutter et al., 1997). Thus, parents will

have learned to tailor their care to the past behavior of their child. It then

becomes very difficult to ascertain the extent to which parental care is truly

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a cause of future child behavior, rather than a result of past child behavior.

This is often called the problem of simultaneous causation, and ignoring it

can lead to simultaneity bias. As a result, researchers have come to appre-

ciate the crucial importance of testing for the direction of causal influence.

Simultaneity bias can lead to absurd findings. For example, one might infer

that talking baby talk to a 3-year-old slows down expressive vocabulary

when, in fact, a child’s failure to speak has driven a parent to use baby talk

in a frantic attempt to elicit speech.

As in the case of selection bias, researchers have devised a variety of

clever strategies for controlling simultaneity bias (Duncan et al., 2000).

The most satisfactory is the randomized experiment, but again, such experi-

ments on humans may be impossible for ethical or practical reasons. Care-

ful, repeated assessments of both the causal factor and the outcome, com-

bined with sophisticated statistical analyses, can be very helpful, although,

once again, undetected sources of simultaneity may always exist (Robins

and Greenland, 1992).

In sum, detecting causal connections is basic to developmental science,

yet threats to valid causal inference, including selection bias and simultane-

ity bias, are often substantial. A variety of strategies can cope with these

biases, including experimentation on animals, experimentation on humans

under special circ*mstances, and nonexperimental studies that are designed

to address threats to causal inference and may also rely on statistical adjust-

ments. Studies using these strategies have different strengths and weak-

nesses. For this reason, strong causal inferences are rarely justified by a

single study. Rather, evidence in favor of a causal connection becomes

convincing when the findings from a variety of studies having varied

strengths and weaknesses converge, especially when the evidence is consis-

tent with the best available theory. The connection between prenatal sub-

stance use and infant outcomes is a good example: although experimenta-

tion on humans is difficult, convergent evidence from a variety of animal

and human studies supports quite strong conclusions about effects.

CAUSAL INFERENCE IN APPLIED RESEARCH

The evaluation of interventions designed to improve children’s early

experiences and outcomes is an important component of early childhood

research. Intervention studies can provide an especially strong means for

testing theories about the developmental significance of early experiences.

Government-subsidized early childhood intervention programs, nutritional

supplements, home visitation programs, and parent training programs are

but a few examples. Program evaluations enable policy makers to assess

how program funds are being spent, whether and to what extent programs

are being implemented as planned, and, ultimately, whether program par-

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ticipation is having positive effects on those served and, if so, why. Know-

ing that an intervention met its goals is a step in the right direction, but the

real need is to move from this general conclusion to specific conclusions

about which aspects of the intervention have which effects, to what degree,

and under which circ*mstances (Rutter et al., in press). Assessing program

impact on those served is once again a causal question. As in more basic

research, threats to valid causal inference arise. Selection bias occurs when

characteristics that predict program participation are also associated with

outcomes. Simultaneity bias can also occur, especially when program ac-

tivities and outcomes are studied over time.

There is, however, an important distinction between the kinds of causal

questions that arise in basic research and those that arise in program evalu-

ations. Basic developmental science typically assesses causal connections

between events that unfold naturally over time. Opportunities for experi-

mentation are limited. In contrast, program evaluations assess the effects of

deliberately planned interventions—activities that would not occur in the

absence of a new policy. For this reason, it is often more plausible, both

ethically and logistically, to conduct experiments in program evaluation

than in basic developmental science.

Such experimentation not only provides strong causal inferences about

the impact of the program, but it can also provide new insights of great

relevance to basic research. Experiments such as the Infant Health and

Development Program (Gross et al., 1997), the High/Scope Project

(Schweinhart et al., 1993; see Chapter 13) study of the long-term effects of

high-quality child care, the Abecedarian Program (Campbell and Raney,

1994, 1995), and the Nurse Home Visitation Program (Olds et al., 1986,

1999) provide a wealth of knowledge about how early environmental en-

richment affects short- and long-term cognitive and social development,

knowledge that would otherwise be unavailable. Experimental evaluations

have also shown that some promising ideas do not appear to translate into

better childhood outcomes, a result that requires a deeper reflection on the

validity of the theory behind the program, as well as on program implemen-

tation. This interplay between basic and applied research is essential to the

vitality of the field.

This discussion may seem to imply that all program evaluations should

be randomized experiments. Although we strongly suspect that random-

ized experiments are underutilized in program evaluation research, they are

not the right tool for addressing all questions about interventions and

special conditions must hold before a randomized experiment is feasible or

desirable. Moreover, well-planned experiments can unravel.

Randomized experiments are of use when a clearly stated causal ques-

tion is on the table. Many program evaluations are designed to answer

other kinds of questions. Early in the life of a new program, the key

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question may be whether the program can be implemented as planned,

whether the participants for whom the program is designed actually partici-

pate, and how much the program costs. A test of the impact of the program

generally makes sense only when the program is based on sound theory

regarding modifiable mechanisms that are associated with the outcomes of

interest (e.g., reducing maternal smoking will enhance newborn outcomes),

when one is confident that the program can be faithfully implemented, and

when there is reasonable assurance that the children and families of interest

will participate as planned. A premature and expensive test of impact can

be a waste of money and can demoralize those who are trying to invent

promising new programs. The results from such an evaluation are difficult

to interpret, creating confusion rather than clarification about policy and

theory. Indeed, premature causal evaluation can undermine potentially

promising programs.

Logistical and political considerations are also extremely important.

Suppose that a new program is ready for a test of its impact. A randomized

experiment often becomes an attractive option, yet the decision about how

to design a causal-comparative study must be made on a case-by-case basis.

Randomized experiments are often feasible and ethically defensible. For

example, when funds become available for a promising new intervention,

there will often be considerable interest among parents in participating but

insufficient resources to accommodate all interested families. In this set-

ting, a lottery can be used to select who will participate—in effect, a ran-

domized

selection. If the results of the randomized experiment are promis-

ing, resources may then become available to accommodate more families.

However, in other cases, randomized experiments may not be feasible or

desirable for logistical or political reasons. In still other cases, it may

already be known from previous experimentation that a program works

under the special conditions of the experiment. The question then may be

whether the program produces significant effects in a routine (nonexperi-

mental) setting. Nonexperimental methods are then required to cope with

selection and simultaneity biases.

It is also important to recognize that an initially randomized experi-

ment can deteriorate under the impact of noncompliance, becoming a

nonrandomized experiment, also called a “quasi-experiment.” An inter-

vention often calls for a degree of investment on the part of participants

that some, or many, find difficult to manage; they may drop out quickly, or

attend training meetings sporadically, or “forget” to be at home when the

home visitor is scheduled to arrive. The same processes are not at work

with the comparable set of control families not receiving the program.

Thus, in longitudinal evaluations, “differential attrition” arises and selec-

tion bias remains a problem despite efforts to conduct a randomized experi-

ment. Even in these cases, however, it is important to keep in mind that the

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resulting quasi-experiment is likely to be much less biased than if no ran-

dom assignment is attempted and parents are free to enroll children in the

program or not. Moreover, few experimental evaluations are now imple-

mented without ongoing monitoring of attrition and other forms of treat-

ment attenuation. This means that attrition can be detected early, efforts

can be undertaken to reduce it, and these efforts can be used to improve the

quality of subsequent implementation (see Shadish et al., in preparation).

Finally, statistical techniques are now available for obtaining relatively

unbiased estimates of program effects despite noncompliance (see Little and

Yau, 1998). In brief, they involve assessing effects of “the intent to treat”

and examining the effects of the program on participants who received

different “dosages” or amounts of the program. These advances have gone

a long way toward addressing some of the problems to which randomized

experiments can succumb.

Even when a randomized experiment is impossible or unadvisable,

however, “experimental thinking” is central to success of causal or com-

parative studies. Nonexperimental evaluations of program impacts can be

viewed as more or less accurate approximations of “the experiment we

wish we could conduct but cannot.” The more accurate the approximation,

the stronger the confidence that the evaluation has produced a valid causal

inference. To understand why this is so requires an understanding of

current thinking in statistical science about the nature of causation and the

logic conditions for valid causal inference (see Appendix B).

In short, this involves thinking hard about the randomized study one

would conduct if it were feasible and ethical. First, we must be able to

imagine an experiment in which each participant is randomly assigned to

the treatment groups. In studying the effects of divorce on children, for

example, we cannot randomly assign parents to obtain or not obtain a

divorce. But we can imagine such an experiment and thus conceive of a

child’s potential outcome under both conditions (the child’s outcome if the

parents were or were not divorced). In a randomized experiment, the

propensity for one’s parents to divorce would be independent of the poten-

tial outcomes—the outcomes that would be observed if divorce did or did

not occur. Although such an experiment is impossible, it can be approxi-

mated by studying the propensity of couples to get divorced. For example,

it might be possible to find, for each child of a divorced family, a child in a

nondivorced family whose parents had the same predicted propensity to be

divorced. These matched pairs might then be compared on outcomes.

In imagining this study of divorce, it becomes clear that there will be

many children of nondivorced parents with very low propensities to be

divorced. In an analysis using propensity-score matching, such cases are

likely to be discarded, because there may be no good match—no child

whose parents were divorced but who had a low propensity to be divorced.

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One might ask whether discarding those cases with low risk of divorce is

sensible. Although statisticians generally dislike throwing away data, the

argument here is that discarding those cases is indeed sensible. The causal

question really has meaning only for those families for which divorce is a

plausible course of action. It makes little sense to compare children of

parents with strong marriages to children of parents who divorce as a

strategy for understanding the effects of divorce. A vivid demonstration of

this point is available in Cherlin et al. (1991).

This last paragraph raises a crucial point about causal inference. There

are often causal questions that are of interest only for a subset of the

population. Whether to have heart bypass surgery is not a relevant ques-

tion for persons with good cardiovascular health. And no one would

conduct a randomized experiment in which persons with such good health,

along with others, were randomly assigned to heart bypass surgery. This is

not only an ethical concern. The impact of heart bypass surgery on persons

with good cardiovascular health is not an interesting question for policy.

Yet it is quite common to find researchers using survey data, for example,

to examine “the effects of divorce” or the effect of low birthweight or the

effects of infant care in an analysis using all participants. Such an analysis

would use statistical procedures to control for extraneous variables. Yet

participants with no chance or a very small chance of experiencing divorced

parents or low birthweight or infant child care really contribute little or no

useful information about the causal question of interest. Thus, the inclu-

sion of such cases may distort findings. Thinking about the populations for

whom the “treatment” is relevant is intimately connected to the problem of

generalizing from an experimental study to a different population, with a

different variant of the intervention or treatment, with a different kind of

outcome measure, in a new setting, and sometime in the future. We now

turn to these issues of causal generalization.

CAUSAL GENERALIZATION

Studies of causal connections in early childhood research involve ex-

plicit generalizations from the sampled domains of people, settings, times

and contexts, causes, and effects to other situations in which the results

might be applied (see Cook, 1990, 1993). Generalizability involves the

inference that a research result arising in a given setting at a given time for

a given set of participants, under a specific version of a treatment and for

specific outcomes is likely to hold in some other setting at a later time with

some other participants, under somewhat different versions of the treat-

ment, and for somewhat different ways of assessing the outcomes. When

applying research results from an intervention study to a natural setting,

one is assuming that: (a) the “treatment” would be implemented in the

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80 FROM NEURONS TO NEIGHBORHOODS

natural setting similarly, but not necessarily identically, to how it was

implemented in the study, (b) the participants in the natural setting would

respond similarly to how the participants in the study responded, (c) the

effects of the treatment would be assessed similarly, and (d) events have not

transpired over time to change the broader context in which the treatment

is being implemented and assessed. In research on early childhood inter-

ventions, the effectiveness of the intervention often depends on the knowl-

edge and skill of the practitioners—those who provide home visits, child

care, or parental counseling—and on other services available in the commu-

nity (see Olds et al., 1998). It is essential that researchers vividly describe

the characteristics of those implementing the treatments; the training, skill,

and supervision required to implement them effectively; and the resources

available within the community where the program is being replicated.

Such descriptions will help determine whether the conditions that may

facilitate the success of the program are present in the natural setting.

Defining the target population—that is, the families and children in-

tended to benefit from a program (or assumed to be affected by the risk

factor of interest)—is also essential, and a well-crafted statistical analysis

can provide useful information on how children of varying backgrounds

respond to a causal variable. Ideally, study participants would be a prob-

ability sample randomly selected from a well-defined target population—

that is, the universe of families and children for whom the causal question

is relevant. A probability sample is obtained when every element (e.g.,

family or child) in the target population has a known, nonzero probability

of being included in the study. Such a sample makes it possible to compute

estimates of effects that are unbiased for the target population.

Randomized experiments, however, rarely involve probability samples

from well-defined populations. Some effort is generally required to con-

vince child care providers or pediatricians or parents or children to partici-

pate in a randomized experiment, generally making random selection from

a population impossible. And cost concerns and logistics generally require

that randomized experiments be carried out in local settings. A nationally

or regionally representative sample is generally far too dispersed to be used

in an experiment.

The trade-off between causal credibility and representativeness is

known in the methodological literature as the trade-off between internal

and external validity (Cook, 1993; Cook and Campbell, 1979). “Internal

validity” is the validity of a causal inference, the kind of credibility obtained

from a well-run randomized experiment. “External validity” is the validity

of generalizations made from the study to the practical setting in which a

new treatment or program might be implemented, the kind of credibility

that might come from a survey based on a probability sample. The trade-

off arises in part because it is usually impossible to conduct experiments on

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participants who have been sampled with known probability from the

population of interest. It also arises because the special circ*mstances

required to construct a randomized experiment often create a research

scenario (settings, implementers, and participants) that is quite different

from the settings of practical interest. Yet even having a probability sample

of settings, implementers, and participants from the population of interest

would not, in itself, guarantee a high level of external validity—what is

called “generalizability.”

To illustrate this point, suppose that a home visitation program works

very well for families of type A but very badly for all other families (families

of type B). Also suppose that the researcher is unaware of this fact and has

the luxury of conducting a true experiment on a random sample of families.

The researcher might then report that “the average treatment effect is near

zero.” While such a statement may be true, it would disguise the reality that

the treatment had a very good or a very bad effect, depending on the type of

family. Thus, the conclusion, even though based on a seemingly perfect

design, would be misleading. The generalization would apply to no one,

neither to families of type A nor of type B.

In this situation, it is essential to consider the concept of a “modera-

tor,” a preexisting characteristic of families or children on which the impact

of the treatment and magnitude of the treatment effect depend. It is pos-

sible, for example, that seriously depressed women are less responsive to

home visiting interventions. In this case, maternal depression moderates

the treatment effect and it would be advisable to assess effects separately for

depressed and nondepressed mothers. Using the concept of a moderator,

one can assess the generalizability of a treatment effect in some detail

within a single-site study, across sites of a multisite study, and across stud-

ies in a research synthesis. This kind of investigation is far more manage-

able when randomization is feasible and ethical in each study, because

nonrandomized studies involve confounders as well as moderators. Mod-

erators can, however, be overused. It is critical to choose a priori modera-

tors suggested by previous research that are most plausible theoretically for

subsequent exploration in order to avoid random hunts for moderating

influences in the absence of evidence of program effectiveness.

One of the most common procedures for studying the generalizability

of findings from multiple studies is “meta-analysis” (see the comprehensive

review of Cooper and Hedges, 1994). A meta-analysis can be thought of as

an unplanned multisite study. If it had been jointly planned by all of the

investigators, care would have been taken to ensure that similar outcome

variables were used in every study; that treatment conditions were stan-

dardized; and that key dimensions of site-level variation were incorporated

into the design. As a retrospective form of inquiry, meta-analyses do not

have the luxury of capitalizing on such planning. Nevertheless, a stream of

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inquiry on a common set of hypotheses in developmental research usually

includes interesting variation in participants, implementers, sites, and treat-

ment conceptions, as well as interesting variation in methodological ap-

proaches. Using meta-analysis, it is possible to exploit this variation to

study intensively the degree of generalizability of a treatment effect and the

specific sources of variation in the treatment effect.

CAUSAL INFERENCE AND GROWING CHILDREN

Growth and change are pervasive and typically rapid during early child-

hood. For this reason, studies using repeated measures on each outcome

are common. There are good reasons to do longitudinal studies: cross-

sectional differences in height, weight, vocabulary, quantitative reasoning,

and motor control may be of little interest compared with understanding

children’s growth trajectories on each of these outcomes. An intervention

to enhance growth in any of these areas can affect cross-sectional status

only by deflecting the growth trajectory. Over time, a shifted trajectory—

what we refer to throughout this report as shifting the odds—will produce

substantial shift in expected status, but the shift in growth rate is the

leading indicator. Studies of causal effects on growth may be significantly

more powerful than studies of

status, particularly when the number of

participants is strongly constrained by cost or logistical issues.

In principle, all of the ideas we have discussed apply to studies of

growth as well as developmental status, if we simply reconceive the out-

come as some interesting aspect of growth, such as an average rate of

change or an acceleration rate rather than a cross-sectional outcome. How-

ever, assessing growth poses special problems of measurement, design, and

analysis. Measuring growth is challenging for such psychological outcomes

as vocabulary or quantitative reasoning, less so for physical characteristics

such as height and weight. New design challenges arise in experimental

studies because repeated measurements pose a risk of attrition, and because

subtle forms of confounding can arise that are not present in cross-sectional

research. Methods of analysis are typically more challenging as well.

Growth curve analysis has a long history in biology and medicine.

Models for growth in stature during childhood, for example, have been

developed and refined over many years. In measuring human height (or

weight or lung capacity, for example), there is little disagreement about the

meaning of the construct being measured or about the units of measure-

ment (e.g., centimeters, grams, cubic centimeters). Unreliability of mea-

surement is not a large problem.

Measuring growth in psychological domains (e.g., vocabulary, quanti-

tative reasoning, verbal memory, hand-eye coordination, self-regulation) is

more problematic. Disagreement is more likely to arise about the definition

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of the construct to be assessed. This occurs, in part, because there are often

no natural units of measurement (i.e., nothing comparable to the use of

inches when measuring height). As a result, units of measurement must be

created and defended, and errors of measurement are likely to be quite

large. This becomes especially problematic when the outcome of interest

changes as children mature—as is the case with achievement outcomes—or

when transitions are involved, as with the development of literacy. For

example, once a child acquires visual recognition memory (between 3 and 9

months), it becomes more appropriate to assess the number of words the

child knows and, later, to assess prereading skills. To compound this

problem, it can be hard to reach agreement about the appropriate age range

for which a particular psychological construct is relevant. Nevertheless,

growth in these psychological domains is of great interest. Many important

interventions are designed to enhance psychological growth, and theories of

development depend on hypothesized causal chains that explain human

variation in the rates of such growth.

Another obstacle to studies of change is the cross-sectional orientation

of psychometrics. When social scientists speak of reliability of measure-

ment, they are almost invariably describing cross-sectional reliability: that

is, the reliability with which one can distinguish among individuals at any

given time. The study of cross-sectional individual differences, especially

differences in cognitive functioning, has had a powerful and enduring influ-

ence on the theory and practice of measurement in psychology. Only

recently have researchers begun to take seriously the reliability with which

one can distinguish among individuals in rates of change, acceleration, or

other aspects of developmental trajectories (see Willett, 1988, for a review).

An example may prove instructive. Consider Figure 4-1, which dis-

plays expressive vocabulary as a function of age for three children, based on

the work of Huttenlocher et al. (1991). The researchers took pains to

estimate the total number of words in a child’s expressive vocabulary on

each of multiple occasions during the second year of life, a period during

which vocabulary rapidly grows from a starting point near zero at age 12

months. Note that a curved line with positive acceleration neatly fits the

repeated measures for each child. What is distinctive about each child’s

growth record is not the starting point (vocabulary is near zero at age 12

months for all three children) nor the standing of the child at any time

point, but rather the rate of acceleration for each child. This rate of

acceleration is increasingly well measured as time points are added. Subse-

quent analyses found a strong relationship between maternal speech and

vocabulary acceleration. The statistical power of such analyses was

strengthened by the fact that it effectively incorporated all the data in a

single analysis. That is, every occasion of measurement contributed to

understanding a single crucial aspect of growth (acceleration), enabling the

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84 FROM NEURONS TO NEIGHBORHOODS

researchers to discover relations that had proved elusive in studies of change

in relative status.

The following appear to be the key ingredients in studies of quantita-

tive growth:

• A clear definition of the outcome variable or construct on which

children are believed to be growing.

• A measurement unit or scale that has constant meaning over the age

range of interest (e.g., height in inches or the number of words in a

child’s expressive vocabulary).

• An outcome that can be measured on a common scale across ages,

such that the alternative, age-appropriate forms of the assessment

can be equated, that is, put onto the same meaningful scale.3

• A statistical model for individual change over time. During the

second year of life, for example, the appropriate model for vocabu-

lary is a positively accelerating curve, as depicted in Figure 4-1.

• A longitudinal study that is optimally designed to ensure a given

level of statistical precision for the question at hand. Trade-offs

among the length of the study, the frequency of observation, and the

sample size are invariably involved.

These design choices strongly affect the reliability and validity of individual

measures of change.

These choices can also affect the internal validity of quasi-experimental

studies. Experts on developmental change have emphasized the value of

interrupted time-series designs when children are growing, especially when

randomized experiments are not feasible (Bryk and Weisberg, 1977;

Campbell and Erlebacher, 1970; Glass et al., 1972; Porter, 1967; see also

Blumberg and Porter, 1983). In these designs, multiple pretreatment obser-

vations are taken in order to establish a pretreatment trajectory for the

children. Figure 4-2 illustrates the value of this approach. Designs that

include only one pretest before a treatment or intervention, followed by a

posttest after the treatment (see shaded portion), cannot distinguish whether

the apparent gains made by the participants (thick line) compared with the

3Standardization within age, as is common in IQ tests, eliminates the possibility of a mean-

ingful scale with respect to the construct of interest (e.g., cognitive ability) and therefore

distorts the study of growth on that construct. Such standardized scales can exhibit shifts in

the relative standing of persons, but they cannot reveal rates of growth with respect to the

behavioral domain. One typical result is that individual differences in estimates of change

become substantially less reliable after standardization, undermining the capacity of interven-

tion studies to discover effects.

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MAKING CAUSAL CONNECTIONS 85

12 14 16 18 20 22 24 26

Age (months)

800

600

400

200

(

)

Actual word count:

Child 1

Child 2

Child 3

FIGURE 4-1 A sample of individual vocabulary growth trajectories. SOURCE:

Huttenlocher et al., 1991. NOTE: •, ∆, and ❏ represent actual word counts for

three individual children.

FIGURE 4-2 Distinguishing treatment effects from growth in time-series designs.

Pre-pretest Pretest Posttest

Participants

Controls

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86 FROM NEURONS TO NEIGHBORHOODS

controls (thin line) are attributable to the intervention. If an additional

pretest had been given, however, it would be possible to tell if the treatment

actually accelerated the growth of the treated children relative to the con-

trols (see thick line from the pre-pretest to the pretest for the participants)

or if the children were already showing different rates of growth prior to

the treatment (see dashed line). In this later case, the treatment actually had

no effect; these patterns of growth would have been predicted without the

intervention.

In sum, it is often essential in studies of early childhood development to

recognize that children are rapidly growing. Causal inference on aspects of

child growth poses important issues that extend beyond efforts to make

causal connections between an intervention and a set of child outcomes at a

given age. When the growth of interest is psychological, it is challenging to

define clearly the dimensions on which children are growing, to devise

assessments that are sensitive to growth, and to evaluate the capacity of

alternative designs to reliably gauge individual differences in growth. For-

mulating and criticizing statistical models is essential to defining causal

effects and considering threats to valid inference. Explicit models are espe-

cially important in cases in which participants are rapidly growing, because

the meaning of growth and of causal effects on growth must be made

explicit if progress is to be made in assessing the quality of the assessments

or the utility of alternative designs for capturing these causal effects.

CONCLUSIONS

At the beginning of this chapter, we emphasized the importance of

combining insights from basic and applied research to gain a fuller under-

standing of early development and the influences that guide and affect it.

Basic research is designed to provide detailed observations of development

and to test theories about causal mechanisms. It is often difficult, however,

to meet the conditions that lead to strong causal inferences. In contrast,

applied research avails itself of interventions and natural experiments that

can often provide better evidence of causation and, when studies are de-

signed appropriately, can help to specify the mechanisms involved. The

challenge to researchers is twofold. The first involves designing studies and

evaluations that successfully capture causal information. The second is to

integrate the evidence from basic and applied research to evaluate alterna-

tive explanations for development and discern their implications for poli-

cies aimed at improving children’s life chances.

In the final analysis, knowledge is advanced not through a single, deci-

sive study, but by integrating evidence generated by different strategies,

with different strengths and weaknesses. The research that generates this

knowledge is, under the best of circ*mstances, a cumulative process that

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MAKING CAUSAL CONNECTIONS 87

starts with rich descriptive data about the phenomena of interest, moves to

understanding connections between outcomes and important influences on

them, and finally seeks to identify causal relations and mechanisms. This

chapter has focused on the final stage of this sequence, given its importance

to both theoretical and political debates about the role of early experience

in child development. Its purpose has not been to assert the superiority of

causal studies, but rather, when causal questions are being addressed by

research, to illustrate the key issues that arise and the critical importance of

being tough-minded about ensuring that the conditions for making valid

causal inferences are met. Only when the limits of current knowledge and

the best thinking about improved designs are clear can we plan research

that will contribute significantly to knowledge in the future.

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From Neurons to Neighborhoods: The Science of Early Childhood Development

The Nature and

Tasks of Early

Development

etween the first day of life and the first day of kinder-

garten, development proceeds at a lightning pace like

no other. Consider just a few of the transformations that occur during this

5-year period:

• The newborn’s avid interest in staring at other babies turns into the

capacity for cooperation, empathy, and friendship.

• The 1-year-old’s tentative first steps become the four-year-old’s pir-

ouettes and slam dunks.

• The completely unself-conscious baby becomes a preschooler who

not only can describe herself in great detail but also whose behavior

is partially motivated by how she wants others to view and judge

her.

• The first adamant “no!” turns into the capacity for elaborate argu-

ments about why the parent is wrong and the preschooler is right.

• The infant, who has no conception that his blanket came off because

he kicked his feet becomes the 4-year-old who can explain the elabo-

rate (if messy) causal sequence by which he can turn flour, water,

salt, and food coloring into play dough.

It is no surprise that the early childhood years are portrayed as forma-

tive. The supporting structures of virtually every system of the human

organism, from the tiniest cell to the capacity for intimate relationships, are

constructed during this age period. The fundamental capabilities that en-

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90 FROM NEURONS TO NEIGHBORHOODS

able human beings to explore and learn about the world around us emerge

and become remarkably sophisticated. The child becomes a social being

with an array of deeply important relationships. Language is acquired and

powerful communicative capacities develop. And, the child’s emotional

repertoire and awareness grow to encompass both tremendous joy and

deep sadness. The tasks to be accomplished range from developing day-

night rhythms to acquiring a rudimentary moral code to learning how to

negotiate and sustain friendships.

At the same time, virtually no one argues that a given child’s life course

is set by the time of school entry. People are not like rockets whose

trajectory is established at the moment they are launched. Indeed, it is the

lifelong capacity for change and reorganization that renders human beings

capable of dramatic recovery from early harm and incapable of being in-

oculated against later adversity. This lifelong plasticity renders us both

adaptive and vulnerable.

Development depends on both stability and flexibility—it is not a zero-

sum game that sets the importance of the early years against the value of the

later years. The real question is not which matters more—early or later

experience—but how is later experience influenced by early experience?

This directs attention to the early childhood years not because they provide

an unalterable blueprint for adult well-being, but

because what is learned at

the beginning of life establishes a set of capabilities, orientations to the

world, and expectations about how things and people will behave that

affect how new experiences are selected and processed. The infant who has

learned that he can engage his parent in play and make objects do what he

wants them to do acquires a fundamental belief in his ability to affect the

world around him. The toddler who has learned that the people she de-

pends on for comfort will help her when she is distressed is more likely to

approach others with empathy and trust than the toddler whose worries

and fears have been dismissed or belittled. The preschooler who has rou-

tinely cuddled into an adult’s lap and read books before going to bed is

more likely to enter kindergarten with a keen interest in reading. The child

who has missed these experiences may have a hard time recapturing them

later in life. In short, getting off to a good start in life is a strategy for

increasing the odds of greater adult competence.

What do we know about how many young children are getting off to a

good start? It would seem logical in a report of this nature to include

information about trends in the well-being of young children. In fact, as a

nation, we have surprisingly little information of this nature. We know far

more about trends in the conditions, such as poverty and use of child care

(see Part III), that affect young children than we do about the children

themselves.

The data that are available present a very mixed picture (for an excel-

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THE NATURE AND TASKS OF EARLY DEVELOPMENT 91

lent overview, see U.S. Department of Health and Human Services, 1999a).

While the nation has made impressive inroads in reducing infant mortality,

rates of premature births and low-birthweight babies are increasing (see

Chapter 8). Among other health indicators (not covered in this report),

immunization rates have increased and lead exposure and unintentional

injuries have declined substantially, but the percentage of young children

living in poverty with activity limitations has risen and the incidence of

asthma and chronic sinusitis has increased substantially for all children.

The incidence of overweight school-age children is increasing, but data are

not available on children under age 6. While there are a few signs that

young children’s early literacy is improving, the positive trends appear only

for children who are not growing up in poverty and whose parents speak

English as their native language (see Chapter 6). Rates of child abuse and

neglect have remained constant for children under age 6 over the past

decade (see Chapter 9). We know virtually nothing about trends in the

incidence of mental health or behavioral problems affecting young children.

Many groups before us have highlighted the tremendous need for better

early childhood indicators in this country (see Hauser et al., 1997; National

Research Council and Institute of Medicine, 1995a), for two recent reports

on this issue); and we enthusiastically concur.

Developmental science does, however, allow us to address the question

of what getting off to a good start means, and it can guide efforts to

improve the nation’s data on young children. These are the issues that we

address in this part of the report. What are the most significant develop-

mental changes that occur during these early years and that, if absent or

seriously delayed, are cause for concern? What early experiences foster

these developments, which undermine them, and how might this differ for

different children?

There are libraries full of books on child development. Our intent was

not to produce a comprehensive handbook that describes every facet of

early development or a guide for parenting that addresses every milestone.

Our review was more circ*mscribed. We sought to identify and discuss

early developmental tasks that, if mastered, appear to get children started

along adaptive pathways and, if seriously delayed or problematic, can lead

a child to falter. We drew heavily on the legacy of research that has fol-

lowed children over time, starting in infancy and preschool, to discern early

precursors of later (and even lifelong) resilience and sustained competence

(see Anthony and Cohler, 1987; Egeland et al., 1993; Garmezy and Rutter,

1983; Masten, 1994; Rutter, 1994; Werner, 1995, 2000). The internal

resources and capabilities and external supports that characterize children

who develop well despite adversity struck us as a fitting departure point for

the exploration of the significant accomplishments of the early childhood

years. Others have conducted similar reviews in recent years (see Carnegie

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92 FROM NEURONS TO NEIGHBORHOODS

Task Force on Meeting the Needs of Young Children, 1994; Damon, 1998;

Ramey and Ramey, 1999), and we benefited tremendously from their work

as well. This led us to emphasize three domains among the many accom-

plishments that characterize the years from birth to age 5:

• Negotiating the transition from external to self-regulation, including

learning to regulate one’s emotions, behaviors, and attention. This captures

the emergence of self-control and independence and can provide an analogy

for the movement toward competent functioning that characterizes devel-

opment as a whole (Chapter 5).

• Acquiring the capabilities that undergird communication and learn-

ing. This includes the early development of language, reasoning, and prob-

lem solving (Chapter 6).

• Learning to relate well to other children and forming friendships.

This highlights the emerging capacity to trust, to love and nurture, and to

resolve conflict constructively (Chapter 7).

The behavioral evidence on these topics provides a rich portrait of how

early development unfolds in interaction with people, things, places, and

events; the conditions under which it appears to get off track; and the

factors that seem to make a difference in whether the child is equipped to

learn, make friends, and enjoy life as a 5-year-old. We close this part by

looking inward at the developing brain (Chapter 8). Not only has the

research on early brain development generated tremendous public excite-

ment, but it also complements what we have learned from behavioral re-

search and points to some areas of special concern. Considered together,

these two streams of behavioral and neuroscience research offer a fuller

portrait of early childhood than does either one considered alone.

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Acquiring

Self-Regulation

uman infants start life as remarkably helpless indi-

viduals who elicit powerful protective responses from

their caregivers. On their own, they would die. In relationships with

protective, nurturing adults, they thrive. Supporting their development,

however, requires sustained patience and adaptation as infants move gradu-

ally and unevenly from needing help in order to do anything, to doing—and

even insisting on doing—many things for themselves. Scientists have found

it useful to capture this transition from helplessness to competence in terms

of the child’s growing regulatory capacity. What does this mean? Initially,

it refers to the mastery of tasks that were accomplished by the mother’s

body or in concert with the mother’s body when the child was in the womb,

but now must be accomplished by the child’s body and through signaling

needs to responsive adults. These tasks include everything from maintain-

ing a normal body temperature to orchestrating physiology and behavior to

conform to the day-night rhythm of human existence, to learning to soothe

and settle once basic needs are met. Later, it means developing the capacity

to manage powerful emotions constructively and keep one’s attention fo-

cused. This chapter addresses these regulatory tasks.

Regulation cuts across all aspects of human adapatation. Living and

learning require people to react to changing events and then to regulate

their reaction. The capacity to react and the toll that reaction takes depend

on the capacity to recover from the reactions. For example, getting upset

by things that are upsetting can be very useful. It motivates people to act to

make life better. But staying upset, ruminating, or carrying negative emo-

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94 FROM NEURONS TO NEIGHBORHOODS

tions around like a talisman can be very destructive to oneself and others.

Mobilizing efforts to explore a new problem or situation is very important

and useful; staying mobilized while working on a problem to the point of

exhaustion and collapse is unhealthy. Adequate adaptation and develop-

ment require reaction and regulation. Infants and young children are often

good at the reaction part, but need help with regulation. Children increas-

ingly develop the ability to regulate their reactions, particularly in support-

ive environments. To reiterate one of our core concepts, development may

be viewed as an increasing capacity for self-regulation, seen particularly in

the child’s ability to function more independently in a personal and social

context.

Reaction and regulation can be seen in all aspects of life, from the

capacity to work harder when one is rested better to the capacity to fight

diseases better when one is able to both turn on and turn off the immune

system more efficiently. Regulation in early development is deeply embed-

ded in the child’s relations with others. In caring for infants, parents are

acting as extensions of their internal regulatory systems. Establishing the

connection between parent and child can be seen as the basic task of the

early months of life. Making that connection is not always easy, however.

It requires the ability to read and understand the baby’s needs and the

knowledge, energy, and resources to respond in ways that are helpful.

Providing the experiences that allow children to take over and self-regulate

in one aspect of their lives after another is a very general description of the

job of parents, teachers, and protectors of children that extends throughout

early childhood and into the adolescent years. The first step in the earliest

days of children’s lives is to establish regulatory connections with them and

then gradually shift the responsibility of regulation over to them in the day-

to-day domains of sleeping, waking, and soothing.

In this chapter, the development of self-regulation is profiled with re-

spect to managing physiological arousal, emotions, and attention. These

are fundamental tasks for the early years, but they entail very different

influences and developmental processes. The reason for considering each a

component of developing self-regulation is that these are the earliest ways

that infants and toddlers learn to manage themselves and begin to acquire

the behavioral, emotional, and cognitive self-control that is essential to

competent functioning throughout life (Bronson, 2000; Kopp, 2000). Each

is important also because it reflects the growing maturity and integration of

several brain areas (particularly in the frontal regions) that enable increased

self-monitoring and deliberate inhibition of undesired behavior (Diamond,

1996; Diamond and Taylor, 1996; Diamond et al., 1994).

These neurobiological changes are consistent with the common obser-

vation that, between birth and age 6, children become increasingly profi-

cient at exercising self-control and applying rules consistently to their own

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ACQUIRING SELF-REGULATION 95

behavior, whether this is manifested in their success at “Simon Says,” their

ability to wait for a cookie, their capacity to remain quiet and still during

religious services, or their capacity to ignore distractions while concentrat-

ing on a task. Further advances in the same brain regions are thought to be

related, at older ages, to the growth of higher-level reasoning, problem

solving (Case, 1992), and planning and executing complex actions, some-

times called “executive control” (Stuss, 1992), which we profile in the final

section of this chapter.

EARLY REGULATORY TASKS

Some cultures celebrate a child’s first birthday at about 3 months after

birth. This recognizes the fact that the child’s life history began at concep-

tion. But interestingly, it also corresponds to what has been called the first

biobehavioral shift in development (Emde et al., 1976). Between 3 and 4

months after birth, there are marked changes in almost every aspect of

infant functioning, from the electrical patterns of brain activity (EEG) (Emde

et al., 1976) to the regulation of visual attention (Rothbart et al., 1994a).

Sharper focus on the first 3 months of life suggests that the entire period is

one of transition, as the baby’s behavior and physiology shift from intrau-

terine to extrauterine regulation (Mirmiran and Lunshof, 1996). The full-

term newborn of normal weight comes into the world well-prepared to

negotiate this transition.

As with all developmental tasks, however, cultural variations in care-

giving practices and individual family differences within cultures affect how

this early transition is worked through. The full range of childrearing

practices around the world appears to confront newborns with markedly

different contexts in which to manage the transition from intra- to extrau-

terine regulation (Barr et al., 1987). Nevertheless, babies adapt, and indeed

thrive, in a wide variety of culturally normative caregiving niches. This

theme of developmental adaptation within cultural variation applies to

virtually all developmental tasks for which we have pertinent data.

Take the !Kung San—a hunter-gatherer culture from the Kalahari

Desert—as an example. The young infant is in constant skin-to-skin con-

tact with her mother, sleeping with her at night and being carried continu-

ally during the day. She is fed breast milk in small amounts approximately

every 15 minutes. Fusses are responded to immediately before they build to

cries. Little or no emphasis is placed on getting the baby to sleep through

the night. At arguably the other extreme, in North America and Europe,

early care typically separates the baby from the caregiver for varying peri-

ods of the day and night. Feedings are larger but more widely spaced. Not

all cries, and certainly not all fusses, are responded to immediately. And

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96 FROM NEURONS TO NEIGHBORHOODS

there is a strong emphasis on encouraging day-night behavioral organiza-

tion and sleeping through the night.

Although intriguing, there are few data on whether or how these differ-

ent practices influence children’s development in the long term. In the short

term, it seems likely that both cultural and individual differences in care-

giving influence what caregivers view as regulatory problems in this early

period. Unfortunately, most of what is known about this has been based on

studies in North America and Europe, where two regulatory concerns per-

meate the pediatric and child development literature: (1) concerns about

establishing day-night rhythms, typically labeled “sleep problems” (Anders,

1979) and (2) concerns about excessive crying (Barr, 1993; Keefe, 1988; St.

James-Roberts and Halil, 1991). These concerns, however, take different

forms even within European-American cultures, as illustrated by compari-

sons between Dutch and U.S. (white) mothers (Super et al., 1996). While

concerns about their child’s sleep patterns were much more evident among

the Dutch mothers, who focused on their own role in imposing regularity

on sleep times, the U.S. mothers were much more likely to use the terminol-

ogy of “problems” when discussing their child’s sleep and to ascribe the

problems to innate tendencies of the child rather than to their own parenting

practices.

While parents raise issues about sleep and crying throughout infancy, they

are particularly evident during this early birth-to-3-month transition period.

Much of the research on these concerns has focused on identifying the under-

lying pathology in the child (Lehtonen et al., in press), yet there is very little

evidence that early sleep and crying problems strongly predict later physiologi-

cal or behavioral problems for otherwise healthy, full-term babies (Elliot et al.,

1997; Rautava et al., 1995; Stifter and Braungart, 1992).

This has led to a more recent, albeit still controversial, approach that

views these problems not as expressions of infant pathology, but as reflec-

tions of how normal individual differences are expressed when infants

attempt to accomplish early regulatory tasks in the context of the dominant

North American/European style of caregiving (Barr, 1990). This perspec-

tive shifts the unit of interest from the baby to the family, and from the

behavior (i.e., crying per se) to what the behavior sets in motion within the

family (Papoušek and von Hofacker, 1998; St. James-Roberts et al., 1995a;

Stifter and Bono, 1998). There is, in fact, some evidence in support of this

more dynamic perspective. These early sleep and crying problems can pose

serious challenges to parents, which create tension among family members,

fuel negative perceptions of the infant, and undermine the parents’ confi-

dence in their caregiving abilities. These detrimental repercussions remain

measurable, at least in some families, later in infancy after the precipitating

behavior has largely passed (Papoušek and von Hofacker, 1998; Raiha et

al., 1995; Rautava et al., 1995).

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ACQUIRING SELF-REGULATION 97

The regulatory challenges of this period are heightened for premature

or medically fragile infants (see Chapter 8 for a fuller discussion). There is

a general consensus that the lower the birthweight, the more difficult the

adjustment to extrauterine life, especially for the babies who are small for

their gestational age and for those born to mothers with low educational

attainment (Georgieff et al., 1989; Ment, 2000; Saigal et al., 1991). Among

very-low-birthweight infants, there are the added risks of serious medical

conditions and long stays in neonatal intensive care nurseries. Thus, each

partner contributes vulnerabilities to the establishment of the mother-infant

dyadic relationship. It is easy to understand that the mother would be

stressed and anxious. The infant, in addition, tends to be much less adept

than the normal newborn in organizing and stabilizing biological rhythms

of sleep, waking, and feeding. He is likely to be more unpredictable, to be

fussier during social interactions, to make less eye contact, to smile less, to

vocalize less, and to show less positive affect—in other words, to be more

difficult and harder for the parent to read (Beckwith and Rodning, 1992;

Barnard and Kelly, 1990). Under these circ*mstances, the caregiver’s abil-

ity to respond sensitively and to cooperate with the infant’s ongoing behav-

ior can be seriously compromised. But even here, a shift in emphasis from

focusing on what is wrong with the baby to identifying caregiving strategies

that provide support for the child’s emerging regulatory competencies can

be most helpful.

Because early intervention efforts, such as home visiting, often begin

during this period, accurate information about early regulatory challenges

may help service providers short-circuit potential corollary problems. Look-

ing in more depth at what is now known about day-night rhythms and

crying can expand the focus from the problem of getting the infant to sleep

or stopping the infant from crying, to a better appreciation of the magni-

tude of the task that the infant is attempting to accomplish, individual

differences in how infants respond during this time of transition, and the

contribution of caregivers’ responses to the success with which these transi-

tions will be made. Accomplishing early regulation is an example of how

the outcomes of developmental processes depend on the relationship be-

tween children and their caregivers.

Acquiring Day-Night Wake-Sleep Rhythms

Humans are diurnal beings who are typically active during the day and

quiet at night. Through eons of evolution, human physiology has come to

reflect this day-night rhythm (Moore-Ede, 1986). Day-night rhythms are

due to both endogenous factors (clocks inside the body) and exogenous

influences (the day-night rhythms in the physical and social world)

(Ikonomov et al., 1998). The internal clock lies deep in the brain in a part

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98 FROM NEURONS TO NEIGHBORHOODS

of the hypothalamus called the suprachiasmatic nucleus (Dickstein et al.,

1998a). It receives information about what time it is outside the body,

generates signals that set the timers or pacemakers of different systems, and

coordinates or synchronizes those various systems.

Newborns don’t seem to know day from night (Anders, 1975). Is this

because their internal clocks aren’t fully mature? Is it because these clocks,

although fully mature, still need to be set to the light-dark, activity-rest

periods of family life? Does the fact that the newborn’s energy needs require

her to eat in the middle of the night keep her clocks from generating robust

day-night rhythms (Wright et al., 1983)? Is she working on pulling together

and orchestrating the rhythms of multiple systems—temperature, blood

pressure, hormone, kidney, liver—that are themselves still maturing (Price

et al., 1983)? We do not know the full answers to any of these questions

yet. However, this list, which could be much longer, gives some of the

flavor of the complexity of the task that faces both the newborn and the

family in sorting out how to differentiate day from night.

Something is known about the facet that affects parents the most:

infant sleep-wakefulness (Coons and Guilleminault, 1982; Elligson and

Peters, 1980; Schectman et al., 1994). Both the structure and temporal

organization of sleep evolves rapidly in the first 3 to 4 months after birth

(Anders, 1975; Elligson and Peters, 1980; Gehart and Maccoby, 1980).

Newborns sleep a lot, typically 16-17 hours per day (Coons and

Guilleminault, 1982; Hoppenbrouwers et al., 1982), and the structure of

sleep-wakefulness more strongly reflects a basic 90-minute rest-activity cycle

than it does a day-night rhythm (Anders, 1982; Coons and Guilleminault,

1982). Total sleep time decreases to about 14-15 hours by 3 months, and

sleeping and waking bouts begin to lengthen and consolidate (Anders et al.,

1992; Bernal, 1973; Coons and Guilleminault, 1982). At birth, the longest

sleeps last about 4 hours, while by 3 months they can be as long as 8 to 10

hours and, for most babies, they occur during the night (Anders et al.,

1992; Bernal, 1973).

Like adults, during long periods of sleep, babies drift up to brief periods

of waking or near waking. Videotaped studies of infant sleep

suggest that

one big difference between babies who sleep through the night and those

who don’t is what happens during these brief waking periods (Anders et al.,

1992). Babies who sleep through rouse briefly and then settle themselves

back into sleep, while those who don’t then cry out and waken their par-

ents. There is some evidence that babies who fall asleep in their cribs

establish patterns of self-settling, while those who fall asleep in contact with

a parent signal when they wake to circ*mstances that are different from

those when they fell asleep. Patterns of feeding also influence nighttime

signaling (and thus parental sleeping through the night) (Wright et al.,

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ACQUIRING SELF-REGULATION 99

1983). Bottle-fed babies lengthen the duration of their longest bout of sleep

a bit faster than do breast-fed babies. While this can sound attractive to the

sleep-disrupted parent, bottle-fed babies also get sick more than do breast-

fed babies (Beaudry et al., 1995). Because the rhythms of other systems,

like growth hormone, cortisol, body temperature, and so on, are orches-

trated in relation to sleep, many suspect that the development and organiza-

tion of sleep helps orchestrate the day-night rhythms in these other systems

(Finkelstein, 1971; Koob, 1992; Weitzman et al., 1979).

Poets and philosophers have long been intrigued by the similarities

between sleep and death. Parents find these similarities more terrifying

than intriguing. Many a parent has probably poked or nudged his or her

soundly sleeping infant to bring about reassuring signs of life. Although

controversial, some suspect that the shorter bouts of sleep characteristic of

early infancy may be protective for babies whose neural systems regulating

breathing, swallowing, and airway clearing are still maturing (McKenna,

1990; Trevathan and McKenna, 1994).

Concerns that very young babies will sleep so deeply that they will fail

to react when air is blocked and oxygen levels get too low have led to the

recent pediatric advice to avoid placing babies on their stomachs during

sleep (American Academy of Pediatrics Task Force on Infant Positioning

and SIDS, 1992). Similar concerns have led researchers to reexamine what

happens when babies sleep alone and when they sleep with others (i.e.,

cosleeping) (McKenna et al., 1993, 1994). Mothers and their 3-month or

older infants have been brought into sleep laboratories, where brain waves,

heart rate, and respiration for both mother and infant can be monitored

throughout the night. Perhaps not surprisingly, mothers and babies don’t

sleep as soundly when they sleep together.

Because both breast-feeding and cosleeping induce shorter bouts and

less sound nighttime sleep, several researchers have speculated that they

protect the very young baby from such things as sudden infant death syn-

drome (SIDS) (McKenna, 1990; McKenna and Mosko, 1990). This is

virtually impossible to prove. Nevertheless, differences in cultural practices

surrounding cosleeping and breast-feeding abound. In this context, it may

be useful to think broadly about how culturally normative variations mesh

with the infant’s developing capacities. On one hand, it is instructive to

recognize that human infants have remarkable capacities to adapt to a wide

range of caregiving practices. On the other hand, understanding practices

that have evolved and been sustained around the world, but are less com-

mon in the United States, can be extremely valuable. Cultural differences

are not arbitrary, nor do they reflect any simple translation from beliefs

into practices; rather they reflect different trade-offs among several goals

that can, in turn, have differing consequences for the infant.

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100 FROM NEURONS TO NEIGHBORHOODS

Learning to Regulate Crying

Crying serves to signal caregivers. Infants of many species produce

calls that serve similar functions. However, only humans cry for no reason

at all (paroxysmal crying) and keep crying after being picked up, fed, and

otherwise apparently made comfortable (Barr, 1990). Folk wisdom says

that there are hunger cries, pain cries, irritable cries, and so on. In fact,

when one hears cries out of context, the likelihood of identifying the cause

of the cry is very poor (Green et al., 1995). Beyond what is causing crying,

caregivers usually want to know how to stop the cries and soothe the

infant.

Although there are marked cultural variations in beliefs about respond-

ing to all fusses and cries, once people do respond, they follow remarkably

similar soothing patterns (Barr, 1990). They say something, touch, pick up,

search for sources of discomfort, and then feed. Parents run through this

repertoire so often in those early weeks and months of a baby’s life that

they could do it in their sleep—and often do, or so it seems. Infants cry in

all of the cultures that have been studied, and interestingly, crying follows a

similar developmental course (Barr, 1990; Barr et al., 1987, 1996). In

caregiving settings as different as the !Kung and North America, crying

makes up more and more of the baby’s (and caregiver’s) day until it peaks,

often around 6 to 8 weeks, and then begins to decline (with the timing of

the peak and decline varying for different babies). But cultural variations in

caregiving practices may influence the amount of crying that characterizes

infants. Comparing the !Kung and North American and Northern Euro-

pean babies, although crying peaks at about the same time, !Kung babies

cry less, even at their peak. Furthermore, it is not that !Kung babies cry less

often, rather that they are soothed more quickly.

Researchers in Canada tested whether they could help North American

babies settle more readily by providing them with more of a !Kung-like

caregiving experience (Hunziker and Barr, 1986). They randomly assigned

families to a condition in which caregivers increased by 2 hours how much

they carried the baby each day. Compared with babies in the control

condition (in which caregivers kept on with their regular practices), babies

who were carried around more shifted their crying toward the !Kung level

of the curve. They did not cry less often, but began to be soothed more

quickly. Unfortunately, the rather dramatic results of this study were not

replicated when something similar was tried in England (St. James-Roberts

et al., 1995b). The Canadian and English studies weren’t identical, and

researchers are still puzzling over whether the differences (in baby slings/

packs, instructions to families, control group rates of carrying, or some-

thing else) might explain the lack of replication. This failure to replicate,

however, probably suggests what parents have long suspected—there is no

magic bullet, except perhaps time. By 12 to 16 weeks, most babies have

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ACQUIRING SELF-REGULATION 101

settled down, spend less of their days crying, seem easier to read, and much

easier to soothe.

There is also some evidence that individual differences in caregiving can

affect crying in the earliest months of life. Babies whose caregivers have

been responsive to their distress and sensitive in reading the meaning of

their somewhat ambiguous cry communications shift more smoothly into

patterns of noncrying communication and spend more time in happier, less

distressed states as the first year proceeds (Crockenberg, 1981). This may

sound like babies have never heard of the laws of learning (i.e., reward the

behavior and it should increase). However,

and Learning.

Dozens of scientists provided articles, papers, chapters, and books. We

are most appreciative of the generous responses to requests for information

that we received from: Lynette Aytch, University of North Carolina at

Chapel Hill; John Barks, University of Michigan; Cathryn Booth, Univer-

sity of Washington; Mary Bowler, U.S. Bureau of Labor Statistics; Sandra

Calvert, Georgetown University; Harry Chugani, Wayne State University;

James Connor, Pennsylvania State University; E. Mark Cummings, Univer-

sity of Notre Dame; Geraldine Dawson, University of Washington; Barbara

Devaney, Mathematica Policy Research, Inc.; Susan Dickstein, Brown Uni-

versity; JoAnn Farver, University of Southern California; Marc Fey, Univer-

sity of Kansas Medical Center; Daniel Goldowitz, University of Tennessee;

Mari Golub, University of California at Davis; John Hewitt, University of

Colorado at Boulder; Jay Hirschman and colleagues, U.S. Department of

Agriculture; Myron Hofer, Columbia University; Carollee Howes, Univer-

sity of California at Los Angeles; Aletha Huston, University of Texas at

Austin; Mark Innocenti, Utah State University; Sandra Jacobson, Wayne

State University; Mark Johnson, Birkbeck College, University of London;

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From Neurons to Neighborhoods: The Science of Early Childhood Development

ACKNOWLEDGMENTS xiii

Jerome Kagan, Harvard University; Peter Kaplan, University of Colorado

at Denver; Eric Knudsen, Stanford University; Mary Clare Lennon, Colum-

bia University; Tama Leventhal, Columbia University; Mark Lipsey,

Vanderbilt University; Bruce McEwen, The Rockefeller University; Editha

Nottelman, National Institute of Mental Health; David Olds, University of

Colorado at Denver; Joy Osofsky, Louisiana State University Health Sci-

ences Center; Bruce Pennington, University of Denver; Tony Raden, Co-

lumbia University; Mabel Rice, University of Kansas; Donald Roberts,

Stanford University; Robert Sapolsky, Stanford University; Mary Schneider,

University of Wisconsin at Madison; Carla Shatz, University of California

at Berkeley; L. Alan Sroufe, University of Minnesota; Phillip Strain, Univer-

sity of Colorado at Denver; Ann Streissguth, University of Washington;

Douglas Teti, University of Maryland at Baltimore County; Edward

Tronick, Harvard University; Delia Vazquez, University of Michigan Medi-

cal School; Peter Vietze, New York State Institute for Basic Research in

Developmental Disabilities; Douglas Wahsten, University of Alberta; Joanne

Weinberg, University of British Columbia; Larry Wissow, Johns Hopkins

University; Fred Wulczyn, Chapin Hall Center for Children, University of

Chicago; Paul Yoder, Vanderbilt University; and Charles Zeanah, Jr.,

Tulane University School of Medicine.

We would also like to thank Gina Adams and Jennifer Ehrle, The

Urban Institute, who provided data from the 1997 National Survey of

American Families; Jerry West and DeeAnn Brimhall, U.S. Department of

Education, who generated multiple tables for us from the 1999 National

Household Education Survey; Paul Newacheck, University of California at

San Francisco, who provided data from the 1996 National Health Inter-

view Survey; Christine Ross, Mathematica Policy Research, Inc., who pro-

vided information about infant child care in the context of welfare reform;

Steve Savner and Rachel Schumacher, Center for Law and Social Policy,

who provided information from the State Policy Documentation Project;

and Kristen Smith, U.S. Bureau of the Census, who provided data from the

Survey of Income and Program Participation.

This report has been reviewed by individuals chosen for their diverse

perspectives and technical expertise, in accordance with procedures ap-

proved by the Report Review Committee of the National Research Council.

The purpose of this independent review is to provide candid and critical

comments that will assist the authors and the National Research Council/

Institute of Medicine in making the published report as sound as possible

and to ensure that the report meets institutional standards for objectivity,

evidence, and responsiveness to the study charge. The review comments

and draft manuscript remain confidential to protect the integrity of the

deliberative process.

We thank the following individuals for their participation in the review

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From Neurons to Neighborhoods: The Science of Early Childhood Development

xiv ACKNOWLEDGMENTS

of this report: Thomas Cook, Institute for Policy Research, Northwestern

University; Roy D’Andrade, Department of Anthropology, University of

California, San Diego; William Danforth, Washington University, St. Louis;

Dale D. Farran, Department of Teaching and Learning, Vanderbilt Univer-

sity; Nathan Glazer, Professor of Education and Sociology, Emeritus,

Harvard University; Jacqueline Goodnow, Department of Psychology,

Macquerie University, New South Wales, Australia; Myron A. Hofer, Col-

lege of Physicians & Surgeons of Columbia University; Jerome Kagan,

Department of Psychology, Harvard University; Sanders Korenman, School

of Public Affairs, Baruch College, City University of New York; Eleanor

Maccoby, Department of Psychology, Stanford University; Barbara Rogoff,

Psychology Department, University of California, Santa Cruz; Michael

Rutter, Social, Genetic, and Developmental Psychiatry Research Center,

Institute of Psychiatry, London, England; and Richard Weinberg, Institute

of Child Development, University of Minnestota.

Although the individuals listed above have provided many constructive

comments and suggestions, responsibility for the final content of this report

rests solely with the authoring committee and the National Research Coun-

cil (NRC) and the Institute of Medicine (IOM).

The committee wishes to recognize the important contributions and

support provided by several individuals connected to the NRC and IOM.

We thank the original members of the Board on Children, Youth, and

Families, under the leadership of its founding chair, Sheldon White, who

believed in the importance of this study from the time it was first proposed

in 1993, and supported the protracted, multiyear search for funding that

culminated in its full implementation. We also thank Kenneth Shine,

Susanne Stoiber, Barbara Torrey, Faith Mitchell, Michele Kipke, and Clyde

Behney for their steadfast support of the project and their critical reviews of

early drafts of the report. We are deeply indebted to Eugenia Grohman,

associate director for reports of CBASSE, who patiently worked with us

through several revisions, and Christine McShane, who provided superb

editorial assistance. Mary Graham patiently proofread the entire report

and has provided superb advice and assistance with report dissemination,

as has Vanee Vines of the National Academies’ Office of News and Public

Information. We are also grateful to Katherine Magnuson at Northwestern

University for her extensive assistance with research on the portions of the

report having to do with family resources and neighborhoods. In addition,

we wish to acknowledge the research assistance provided by Pam Gardner

at the University of Michigan and Jeanette Mitchell and Mariolga Reyes at

the City University of New York and the administrative support provided

by Amy Belue at the Heller Graduate School at Brandeis University.

Finally, it would be impossible to overstate the extraordinary effort and

critical contributions of Nancy Geyelin Margie, research assistant, and

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ACKNOWLEDGMENTS xv

Ronné Wingate, project assistant, who served as the primary administrative

staff for the committee at the NRC. Each of these talented and highly

dedicated individuals played the kind

babies who are never responded

to, such as those who grow up in institutions, often cease crying almost

completely by about the time they are 3 months old. Babies evidently do

learn to stop crying if it is never “rewarded.” The laws of learning actually

say that the most powerful way to keep a behavior going is to reward it

sometimes and not others, termed “intermittent reinforcement.” The laws

of learning would argue that less, but intermittently, responsive parenting

should create a baby who is more fussy and whiny. This, indeed, appears to

be the case. The evidence that responding consistently and readily to the

infant’s cries reduces crying in the long run is not as strange as it first seems.

Not all crying is the same. Some parents live in dread of having an

infant with colic. Colic is a syndrome that has perplexed parents and physi-

cians for ages. It describes a syndrome of excessive, uncontrollable crying

that, following the normal crying curve, also peaks around 6 to 8 weeks

and resolves between 12 and 16 weeks (with lots of variation among babies

in timing and duration) (Barr et al., 1992; Karofsky, 1984; Miller and Barr,

1991). Like other crying, it also clusters in the late afternoon and evening

hours. It differs from noncolic crying primarily in being difficult if not

impossible to soothe. Somewhat arbitrarily, colic is often defined for re-

search purposes by Wessel’s rule of three: fussing or crying for more than 3

hrs/day, for 3 days/week, for 3 weeks (Wessel et al., 1954). How much a

baby with colic cries varies from one day to the next, and from one baby to

the next. Using diaries kept by parents in which they record each crying

bout of 5 minutes duration or more, the crying of infants with colic has

been documented to vary from 3 hrs/day to as much as 6 or more hrs/day.

This compares to the 1 to 2 hrs/day of crying that parents report for babies

without colic. At its worst, a baby with colic may cry most of the time she’s

awake, and, adding insult to injury, she seems to sleep less than babies

without colic (Lehtonen et al., 1994).

The word colic refers to what has seemed to be the obvious source of

this crying: something to do with the digestive system. However, despite

many attempts to identify what is wrong with the baby (i.e., sensitivity to

cow’s milk protein, incomplete lactose absorption, gastroesophageal reflux,

gastrointestinal immaturity, including allergic reactions) thoughtful reviews

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102 FROM NEURONS TO NEIGHBORHOODS

of the data suggest that no more than 5 percent of colic can be attributed to

identifiable pathologies (Gormally and Barr, 1997). That’s not much, espe-

cially considering that the rate of colic may be as high as 10 to 20 percent in

Western cultures.

Even if convinced that babies with colic are not suffering from a physi-

cal disorder, scientists, like the parents, wonder about its implications for

who the baby is and who she will become. By definition, infants with colic

are difficult. But does this mean that they are biologically or constitution-

ally predisposed to have difficult, irritable temperaments once the colic has

passed? The weight of the evidence suggests that this is not true (Elliot et

al., 1997; Rautava et al., 1995; Stifter and Braungart, 1992), but there is

still argument over this conclusion primarily because of the difficulty of

measuring both crying and temperament.

It must be a relief to parents of babies with colic to find that, by about

3 to 4 months, they have an emotionally quite different baby on their

hands. No longer irritable or hard to soothe, the baby’s true temperament

begins to be more apparent. This is true not only of infants with colic. In

general, it is difficult to predict later temperament from behavior in the first

3 to 4 months of life, as infants are going through so many transitions.

Stability in infant temperament appears to increase by 4 months of age.

Recently, developmental psychologists have become quite interested in

identifying the roots of a temperamental pattern that is known as behav-

ioral inhibition. Inhibited toddlers and preschoolers are very shy in social

encounters (Calkins et al., 1996; Rubin et al., 1997), wary of and upset by

novel stimuli, and are thought of by parents and peers as anxious and

fearful (García Coll et al., 1984). The impetus for this interest is twofold.

First, there is growing concern with understanding the developmental path-

ways that lead to later anxiety and depressive disorders. Second, neuro-

science research is revealing the specific neural pathways and neurochemi-

cal processes that underlie fear responses. This work is suggesting

hypotheses about why some children may be extremely anxious and fearful

from an early age.

This has led to several programs of research (see Fox et al., in press;

Kagan and Snidman, 1991; Kagan et al., 1998) on young children who

display fearful, shy, inhibited temperaments to identify both the anteced-

ents and consequences of these characteristic patterns of responding to

people and events. Kagan and his colleagues developed a set of challenges

for 4-month-olds that included highly stimulating sounds, sights, and smells

that are presented to the baby in a set order. Some babies think these

stimuli are great. They smile, coo, and wave their arms around as if to say,

“Give me more!” At the other end of the spectrum, some babies find the

stimulation to be too much. They fuss, arch their backs, cry, and struggle,

as if to say, “Take them away!” When babies are tested at 2 months, how

they react to these challenges doesn’t predict later temperament. However,

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by 4 months, reliable differences emerge. Babies who react positively are

more likely to become busy, active, boisterous toddlers—some would say a

handful, others refer to them as exuberant. In contrast, those who find the

stimulation to be too much are more likely to be fearful and shy as toddlers

and preschoolers. This evidence suggests that, for some children, negative

reactivity to novel stimuli as infants evolves into a shy, inhibited, anxious

temperamental pattern by toddlerhood.

This is not a trivial phenomenon. About 20 percent of healthy, Euro-

pean-American samples display negative reactivity to novel stimuli as young

infants (Kagan et al., 1998). About one-third of the reactive infants studied

by Kagan and his colleagues remained highly fearful of unfamiliar events at

14 and 21 months, and 13 percent of these infants continued to show

subdued and shy behavior with unfamiliar adults and peers at 4 1/2 years of

age (Kagan et al., 1998). At age 6, the inhibited children continued to be

socially wary and reticent during their interactions with peers and an adult

experimenter, and they exhibited signs of physiological stress (Kagan et al.,

1987). Researchers who have focused on the socially reticent behavior of

these children have found contemporaneous associations with maternal

reports of both shyness and internalizing behavior problems (Coplan et al.,

1994). Recently, inhibited temperamental patterns have been associated

with a physiological pattern of resting right frontal EEG activation (Calkins

et al., 1996; Fox et al., 1995, 1996; Schmidt and Fox, 1994), which appears

to be associated with a tendency to respond to stressful events with negative

affect or depressive symptomatology (Davidson, 1992). Fox and his col-

leagues (in press) have recently linked this physiological pattern at 9 months

of age to continuity in behavioral inhibition up to age 4. We refer to the

same physiological pattern when we discuss the developmental conse-

quences of maternal

depression in Chapter 9.

Once caregivers and babies have ridden the roller-coaster of rapid de-

velopmental change through the first 3 months of life and the baby’s behav-

ioral style or temperament seems to be easier to discern, the next task is to

support the baby’s developing abilities to regulate his or her emotions and

behavior.

Although learning to sleep through the night might seem far afield from

controlling outbursts of emotion, learning to wait before acting, self-moni-

toring, and acquiring the ability to organize segments of behavior sequen-

tially—all of which are embraced by the term “self-regulation”—they all

involve various forms of self-monitoring and response inhibition that, in

turn, reflect the growing maturity of the brain, as we discussed at the

beginning of this chapter. The infant’s emerging ability to replace crying

with other forms of communication is just the first step along a develop-

mental progression that recruits the child’s increasing competencies into

more and more mature self-regulatory functioning.

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104 FROM NEURONS TO NEIGHBORHOODS

UNDERSTANDING AND REGULATING EMOTIONS

Emotions color the life experience of young children. They account for

the peaks and valleys of daily life as they are manifested in exuberant peals

of laughter during play, angry defiance when faced with unfamiliar food, or

distress and frustration after a fall. Emotions can contribute to or under-

mine the growth of new skills and competencies in young children. The

interest and pleasure a child brings to mastering new tasks motivates the

development of new abilities. Angry conflict with a parent or a peer can be

a catalyst for new understandings of others’ feelings and motives. On other

occasions, however, heightened emotion undermines a young child’s ca-

pacities to function competently, as any parent witnessing a toddler’s tan-

trum can document. Much of the current interest in early emotional devel-

opment revolves around the young child’s growing ability to regulate and

integrate emotions adaptively into the fabric of social interactions. Both

parents and the public, for example, are interested in ensuring that young

children learn to handle anger and resolve conflicts without resorting to

aggression, to “use their words” instead of hurling a block across the room.

At the same time, understanding the development of emotion regulation

requires a broader understanding of emotional development.

Early emotional development provides the foundation for psychosocial

well-being and mental health. Just 20 years ago, the thought that very

young children could manifest serious psychological disorders was unimag-

inable. Today people recognize that toddlers and preschoolers are subject

to many of the same kinds of emotion-related disorders that have long been

studied in older children, adolescents, and adults. In 1994, a diagnostic

classification scheme was developed to assess emotional and developmental

problems in the first three years of life (Zero to Three’s Diagnostic Classifi-

cation Task Force, 1994), and scientific inquiry into questions of young

children’s mental health has increased exponentially in recent years. Young

children can experience problems related to sad, depressed affect (Cicchetti

and Schneider-Rosen, 1986; Cicchetti and Toth, 1998; Kovacs, 1989), anx-

ious fear (Albano et al., 1996; Thompson, in press(b); Vasey, 1998) and

angry behavioral problems (Shaw et al., 1994, 1996; White et al., 1990).

This emerging knowledge is bringing issues of early emotional development

and regulation to the forefront of discussions about prevention, early detec-

tion, and early treatment of disorders in young children.1 Over recent years,

1Reports of extensive pharmacotherapy for preschoolers with behavioral disorders have

raised critical questions about existing diagnostic and treatment practices for social and emo-

tional problems in young children and related concerns about the general lack of scientific

evidence to guide appropriate intervention (see, for example, the recent NIH Consensus State-

ment on the Diagnosis and Treatment of Attention Deficit Hyperactivity Disorder, 1998).

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ACQUIRING SELF-REGULATION 105

there has also been a growing appreciation for the fact that children grow-

ing up in very different sociocultural contexts develop emotionally in differ-

ent ways as a result of how emotions are socialized. Children learn to

construe their emotional experience in culturally relevant ways (Eisenberg,

1986; Miller, 1994; Miller et al., 1996; Ochs, 1986).

After a brief overview, we describe in more detail what is known about

how young children come to understand their own and other’s emotions

and about the early development of emotion regulation. Throughout, it is

clear that just as it is impossible to understand the construction of a 50-

story building apart from the scaffolding that supported its emerging struc-

ture, it is impossible to understand early emotional development apart from

the parent-child or caregiver-child relationship within which this process

unfolds. In addition, the task of learning how to manage one’s emotions

constructively is a different challenge for children with different tempera-

ments, as well as for their parents.

Emotional Development

Compared with efforts to understand how children learn, the study of

emotion in young children is relatively new. Researchers are still asking

(Mascolo and Griffin, 1998): What is emotional development the develop-

ment of? The answers range from the capacity to identify one’s own feel-

ings, to the development of empathy, to the ability to constructively man-

age strong emotions. All are correct. As more is learned, we are struck by

the richness and complexity of young children’s emotional lives, as well as

by the remarkable accomplishments that they make in this area prior to

school entry.

The ways in which researchers learn about emotional development are

diverse and, in some cases, ingenious. Some have conducted fine-grained

analysis of the facial expressions of young infants in interaction with their

mothers; others have observed family interactions during dinnertime or

bedtime (to obtain rich profiles of the family emotional climate), or en-

gaged in conversations with young children about their understanding of

emotion (often centered around hypothetical stories); still others have inter-

viewed parents or other caregivers about the emotions they commonly

observe in the children they care for. Few of these studies have followed

The committee did not specifically address these vitally important issues and does not include

a discussion of them. This is not to imply, however, that we minimize their significance. To

the contrary, these issues constitute an urgent topic for both scientific inquiry and guidelines

for practice.

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106 FROM NEURONS TO NEIGHBORHOODS

children over more than brief periods of time, however, so knowledge of

emotional development is based largely on looking separately at infants,

toddlers, and preschoolers and piecing together a picture of development

from these cross-sectional data. Moreover, the broad mix of approaches to

studying emotional development has not been matched by attention to the

variety of contexts in which emotions develop and are socialized. Unfortu-

nately, most of what is known has been based on studies of middle-class

white children, despite suggestive evidence that socioeconomic and cultural

contexts confer significant

variability in how children learn to interpret and

express their emotions.

Emotions are biologically basic features of human functioning. They

are governed by very early-developing regions of the human nervous sys-

tem, including structures of the limbic system and the brainstem that have a

long evolutionary history. The capacity of a newborn to exhibit distress,

fear, and rage reflects the early emergence of these biologically deeply

rooted emotional brain systems. Chapter 8 discusses the richly intercon-

nected brain structures and hormonal influences that organize the arousal/

activation and regulatory/recovery interplay of emotional reactions

(LeDoux, 1996; Panksepp, 1998; Schore, 1994). Throughout early child-

hood, other brain regions (especially in the frontal neocortex) progressively

mature and become interconnected with these early-developing brain re-

gions to contribute to the development of more accurate emotion apprais-

als, growing capacities for emotion self-regulation, complex emotional

blends, and other developing features of mature emotional experience.

Individual differences in emotion, insofar as they derive from differ-

ences in temperament, are also biologically rooted. Temperamental quali-

ties, including a child’s typical ways of reacting to events, general mood,

capacities for self-regulation, and activity level, appear early in infancy and,

as mentioned earlier, show signs of stability starting at 4 months. Although

the ways that temperament is manifested in behavior change significantly as

the child matures—the fearful child practices being brave, the highly active

child learns to sit still—these qualities are biologically or constitutionally

based. Some of the most distinctive temperamental features that character-

ize infants at birth are based on emotional response tendencies, whether

they concern the baby’s dominant mood, adaptability, soothability, socia-

bility, or fearfulness of novelty (Goldsmith and Campos, 1982; Goldsmith

et al., 1987). Temperamental individuality is descriptive not just of re-

sponse tendencies, but also of self-regulation (Rothbart and Bates, 1998).

Young children who are reticent or withdrawn in response to new or chal-

lenging situations are displaying a temperamental attribute that is both

emotional in quality (i.e., fearful) and self-regulatory (i.e., inhibited), with

profound implications for their social as well as biological functioning

(Kagan, 1998b). Emotions are, in short, one of the most ancient and

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enduring features of human functioning, and they develop significantly

during the first years of life in the context of social interactions and rela-

tionships.

Emotional development during the first five years offers a window into

the psychological growth of the young child (Denham, 1998; Lieberman,

1993; Saarni et al., 1998; Sroufe, 1996). Newborns’ emotional lives center

on feeling hungry or sleepy, too cold or too hot, and other manifestations of

“state,” and their emotional repertoires seem to range narrowly from cry-

ing to cooing. In contrast, physical states rarely determine the emotions of

preschoolers. Their feelings hinge on how they interpret their experiences,

what they think others are doing and thinking, and how others respond to

them. In early infancy, emotions can be extreme and are not easily regu-

lated by the child or, for that matter, by the parents. By the end of the

preschool years, young children are capable of anticipating, talking about,

and using their dawning psychological awareness of their own and others’

emotions to better manage everyday emotional experience (Thompson,

1990, 1994). Their emotional repertoires have expanded dramatically and

now include such feelings as pride, shame, guilt, and embarrassment that

reflect developing self-understanding and social awareness. Preschoolers

have also become proficient at anticipating other’s emotions, adjusting

their behaviors accordingly, and even hiding their emotions from others, all

important social skills of which the young infant is incapable.

Emotions are, by their nature, relational (Emde, 1987, 1998). They

both emerge from and provide the basis for human attachments, social

communication, and prosocial as well as antisocial encounters with adults

and children (Emde, 1987, 1998; Izard, 1991). A baby’s cries of distress

bring his caregivers to his side; his coos and gurgles illicit playful interac-

tion. Even young infants smile in response to a smile and cry in response to

a cry (Thompson, 1998a). By the end of the first year, infants are acutely

sensitive to the emotional cues of other people, especially in uncertain or

potentially threatening circ*mstances. In a process that researchers call

social referencing, infants take their cues from the reassuring or anxious

expression of a caregiver, which, in turn, can affect whether they continue

to play comfortably or freeze in their tracks (Baldwin and Moses, 1996;

Bretherton et al., 1981; Feinman, 1992; Saarni et al., 1998; Sorce and

Emde, 1981; Sorce et al., 1985; Tomasello et al., 1993; Trevarthen and

Hubley, 1978). By age 2, children begin to show genuine empathy towards

others (Thompson, 1998a; Zahn-Waxler and Radke-Yarrow, 1990). They

not only read and adjust their own responses to others’ emotions; they try

to make others, even their dolls and stuffed animals, feel better. In the years

that follow, a child’s emotional life is shaped by relational influences as

diverse as the security of attachment relationships (Cassidy, 1994; Laible

and Thompson, 1998), parent-child conversations about emotional events

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(Kontos et al., 1994), and parental coaching of appropriate emotional ex-

pressions in social situations (Miller and Sperry, 1987). Emotional devel-

opment is thus a window into how, early in life, developmental change and

responsive relationships are entwined.

The cultural meanings expressed in these relationships also profoundly

affect how children learn to construe and react to their emotional experi-

ences (Eisenberg, 1986; Miller, 1994; Miller et al., 1996; Ochs, 1986).

Cultural values affect how young children learn to interpret and express

their experiences of fear, anger, shame, pride, embarrassment, and other

emotions. They also guide the construction of new emotions and emotional

blends (such as fear-shame, anger-guilt) that color emotional life and reflect

these values. The sociocultural context also guides how emotions are so-

cialized so that, for example, in some contexts experiences like teasing can

serve constructive purposes and in other contexts they can be debilitating to

the socialization of emotion and its expression (Briggs, 1992; Corsaro and

Miller, 1992; Eisenberg, 1986; Miller and Sperry, 1987). As we discuss in

the context of language development (see Chapter 6), emotions are also

socialized in the context of parent-child discourse, as well as in the conver-

sations that young children overhear among the adults around them. Chi-

nese and Chinese-American mothers, for example, are more likely than

European-American mothers in the United States to emphasize moralistic

themes and the shame inherent in misbehavior when recounting their

children’s mischievous behavior to other mothers in the child’s presence

(Miller et al., 1990, 1996). In each case, mothers are interpreting the

child’s experience consistently with the broader values of their culture.

Because of the diverse and powerful ways that parents socialize emo-

tional development, researchers have devoted considerable attention to the

broader emotional climate of the home

environment and its impact on

young children (e.g., Gottman et al., 1997). In typical circ*mstances, young

children are faced with a variety of emotional demands at home and are

assisted in understanding and managing them by the support of their

caregivers. When the emotional climate of the home is undermined—such

as when parents experience marital dysfunction (Cummings, 1987;

Cummings and Davies, 1994a; Davies and Cummings, 1994; Grych and

Fincham, 1990; Lieberman and Van Horn, 1998), or parent-child interac-

tions are conflictual, coercive, or abusive (Gaensbauer and Sands, 1979;

Patterson et al., 1989, 1992), or the parent suffers from depression or other

affective disorders (Dawson et al., 1994; Garber et al., 1991; Zahn-Waxler

and Kochanska, 1990; Zahn-Waxler et al., 1991)—young children are con-

fronted with conflicting, confusing, and sometimes overwhelming emo-

tional demands. To make matters worse, they are often deprived of the

parent as a resource for managing these powerful emotions (Thompson and

Calkins, 1996; Thompson et al., 1995). It is not surprising to find that

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children from homes with serious marital conflict, or who are raised by a

depressed parent, or who are maltreated are more likely than children who

are spared these experiences to experience difficulties in emotion regulation

and, for a small but significant minority, to develop affective disorders of

their own.

What has not been appreciated until recently is that these disorders can

be apparent early in life, as emotional experience is becoming organized in

infancy and early childhood (Emde et al., 1993). Young children growing

up with a parent with an affective disorder are themselves at risk for depres-

sion and other affective disturbances, partly as a consequence of the child’s

overinvolvement with the parent’s emotional state and difficulties in man-

aging the emotional demands this presents (Zahn-Waxler and Kochanska,

1990; Zahn-Waxler et al., 1988). Some young children (especially those

who are dispositionally fearful or inhibited) are prone to anxiety-related

disorders, especially when their temperamental vulnerability is coupled with

anxious or hostile attachments to their caregivers (Cassidy, 1995; Thomp-

son, in press(b); Vasey, 1998). Young children who are abused or neglected

by their caregivers can experience significant emotional and psychosocial

problems, including the display of intense, maladaptive emotions, difficul-

ties in understanding emotion in others, and social incompetence (e.g.,

Beeghly and Cicchetti, 1994; Cicchetti, 1990; Rogosch et al., 1995; Shields

et al., 1994). Seriously problematic parent-child interactions are also one

of the cluster of features that distinguish young children who display con-

duct problems (Shaw et al., 1994, 1996).

These and other illustrations of the development of emotion dysfunc-

tion in early childhood suggest that, as a result of their reliance on the

emotional support of their caregivers in understanding, experiencing, and

managing their own feelings, young children may be particularly vulnerable

to emotion-linked disorders when parent-child relationships are insecure,

coercive, or otherwise troubled. This is especially so because of limitations

in their independent capacities for emotional and behavioral self-regulation

(Cole et al., 1994). Not only are these children failing to receive the posi-

tive supports they require for healthy emotional development; they are

grappling, sometimes on a daily basis, with circ*mstances that undermine

the well-being of many adults.

Learning to Understand Emotions

How do the indiscriminate cries of the infant become the preschoolers’

differentiated feelings of anger, shame, embarrassment, and loss? Research-

ers have made some inroads into understanding how the generalized arousal

conditions of early infancy mature into the more refined emotional states

apparent in older children and adults. Social experiences are a central part

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of the answer (Saarni et al., 1998). In practice, a child’s emotional reper-

toire is socially constructed.

As parents and other caregivers respond to an infant’s emotional ex-

pressions, manage the child’s feelings, and later label and discuss emotional

experience, they help to organize and give meaning to early emotional

experience. For example, parents who discuss emotions more frequently

and elaborate on emotional experiences (e.g., Why do you think Sally is

sad? Do you think she misses her sister? What do you think you could do

to cheer her up?) tend to have children with more accurate and elaborated

understandings of emotion (Brown and Dunn, 1996; Brown et al., 1996;

Denham, 1998; Denham et al., 1994; Dunn, 1994; Dunn et al., 1991;

Nelson, 1993, 1996). Research on children with developmental disabilities

indicates that such conversations are crucially important. However, look-

ing specifically at children with Down syndrome, their mothers are signifi-

cantly less likely to refer to inner states (feelings and cognitive states) during

everyday conversations compared with mothers of normally developing

children, and the children are significantly less likely to talk spontaneously

about feelings and more likely to have delayed expressive language skills

(Beeghly and Cicchetti, 1997; Tingley et al., 1994). Parents also help their

children understand that “how I feel” is not necessarily the same as “how

you feel” and thus foster a growing awareness of other people as their own

actors—an essential building block of social understanding. Parental be-

havior can also serve as a catalyst for early empathic responding, especially

when parents fix their children’s attention on another’s distress and explain

the causes of that person’s feelings (Zahn-Waxler et al., 1992).

Emotion understanding grows in concert with the development of other

forms of knowledge and learning in early childhood. Emotions are objects

of children’s thinking as well as of their feelings. Take, for example, the

burgeoning research on “theory of mind,” which focuses on children’s

developing frameworks for inferring what other people (or children) are

thinking, intending, believing, and feeling and then making predictions

about how they will respond (Astington, 1993; Bartsch and Wellman, 1995;

Flavell and Miller, 1998). Young children, it turns out, are remarkably

perceptive. Even 2-year-olds, for example, understand that people have

inner experiences of perceiving, feeling, and desiring and that they will feel

good if they get what they want and feel bad if they don’t. Four- to 5-year-

olds appreciate the more complex connections between emotions and an

individual’s thoughts, beliefs, and expectations (Bartsch and Wellman,

1995; Flavell and Miller, 1998; Wellman, 1990; Wellman et al., 1995).

They understand, for example, that individual tastes and preferences guide

how people respond emotionally to rock music or a symphony. Their

appreciation of the connection between emotions and expectations appears

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also in their delight in fooling others—such as telling a sibling that the

thermos contains hot chocolate, when water is really inside.

In the years that follow, children begin to understand the dynamics of

emotional experience, including how emotional intensity gradually dissi-

pates over time, how specific emotions are related to certain prior events,

and how a person’s background,

experiences, and personality can yield

unique emotional reactions to events (Gnepp and Chilamkurti, 1988; Har-

ris et al., 1985; Thompson, 1989). Eventually children also begin to under-

stand how a person can experience simultaneously multiple or conflicting

emotions, but this is a conceptual achievement beyond the grasp of most

preschoolers. These are momentous achievements, but the more important

point is that children’s emotional and cognitive development support each

other. Certain emotional understandings and capacities (including regula-

tory capacities) are simply beyond their reach until they have reached cer-

tain levels of cognitive maturity. The combination of emotional difficulties

and communication problems (e.g., major speech delays, hearing problems)

in young children provides a more troubling example of how different

facets of development interact to facilitate or undermine their overall func-

tioning (Prizant et al., 1993).

Understanding emotion is also closely linked to the growth of self-

understanding and, with it, the capacity to experience self-conscious emo-

tions such as pride and shame. Late in the second year and during the third

year, young children begin to call themselves by name, to use “I” and

“mine,” and to assert their new feelings of competence and independence

by insisting on “doing it myself” (Bates, 1990; Bullock and Lutkenhaus,

1988, 1990; Stipek et al., 1990). Along with this newly emergent self-

consciousness, young children begin to exhibit pride, guilt, shame, embar-

rassment, and other self-referent emotions (Barrett et al., 1993; Lewis,

1993; Tangney and Fischer, 1995). Once they have a self, in other words,

young children begin to respond to experiences—good and bad—on behalf

of the self. Catching a ball prompts not only glee, but also pride; spilling

food in one’s lap brings not only discomfort, but also shame and embar-

rassment. Interestingly, this is also the beginning of self-regulation and self-

control (Kopp and Wyer, 1994). These self-conscious emotions are

advanced by the young child’s capacity to see the self as an object of

observation and evaluation by others, to understand behavioral standards,

and to apply those standards to an evaluation of their actions (Kochanska

and Thompson, 1997; Kochanska et al., 1995). Guilt derives, for example,

from the realization of how one’s behavior has departed from an accepted

standard, while pride arises from awareness of how one’s actions have

exceeded what might reasonably have been expected. With these transi-

tions in self-awareness, the young child is an emotionally much different

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person than before. Her emotional life is now colored by the feelings

evoked by others’ evaluations and by her own self-judgments. Emotional

development thus depends on and affects the development of the self.

Learning to Regulate Emotions

As young children acquire a better understanding of emotions, they

become more capable of managing their feelings (Fox, 1994; Garber and

Dodge, 1991; Kopp, 1989; Thompson, 1990, 1994). Emotion regulation is

perhaps the most challenging aspect of emotional development. Regulating

feelings depends on putting understandings about emotion to work in real-

life contexts that can be extremely frustrating, upsetting, or embarrassing.

Even positive emotions require regulation; exuberance is appropriate on the

playground but not in a hospital. The task of emotion regulation is not

simply a matter of learning to suppress emotions. It is more broadly one of

deploying emotions effectively in relationships, while playing and learning,

and in a wide range of settings. The fact that cultures and even individual

families differ in their standards for the appropriate display and manage-

ment of emotions makes this task especially challenging for children who

cross over from one cultural environment (e.g., their immigrant family) to

another (e.g., their preschool, which may or may not reflect their home

culture).

Children start life completely incapable of modulating the expression

of overwhelming feelings, integrating emotions adaptively into the fabric of

social interactions, and deploying emotions in the service of focusing and

sustaining attention. From a very early age, however, infants develop

rudimentary skills for managing their own emotional experiences, in part

by learning to enlist others who can help them. This can be observed

initially in the comfort seeking of a distressed infant or toddler (Thompson,

1990). By the middle of the second year, toddlers can already be observed

making active efforts to avoid or ignore emotionally arousing situations,

engaging in encouraging or reassuring self-talk, changing or substituting

goals that have been frustrated, and other quite sophisticated behavior

strategies for managing emotions (Braungart and Stifter, 1991; Bretherton

et al., 1986; Buss and Goldsmith, 1998; Calkins and Johnson, 1998;

Cummings, 1987; Grolnick et al., 1996; Smolek and Weinraub, 1979; Stein

and Levine, 1989, 1990). By the time of school entry, children’s regulatory

repertoires have become increasingly proficient and flexible as they learn,

for example, that their interpretations of events can affect how they react

and that they can camouflage their emotions if need be (Harris, 1993).

Children who learn to manage their emotions constructively not only

have an easier time with the disappointments, frustrations, and hurt feel-

ings that are so prevalent when they are young—and are presumably hap-

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pier as a result—but they also have an easier time relating to others at

home, in child care, and on the playground, as we discuss in more detail in

Chapter 7. Indeed, the close correspondence between emotion regulation

and relationships with peers has critical implications for efforts to foster

positive social interactions and help young children who have problems in

this area. Acquiring the capacity to regulate emotions also helps children

believe that emotions are manageable, controllable, and can be appropri-

ately mobilized and expressed—in short, that one’s feelings need not be

overwhelming, undermining, or disorganizing —what Saarni (1990, 1999)

calls “emotional self-efficacy.” Children who do not feel in control of their

emotions are more prone to outbursts, inattention, and rapid retreats from

stressful situations, thereby creating a self-fulfilling prophecy (Garber et al.,

1991). Finally, the capacity for self-regulation is a prerequisite for the

critical task of learning to comply with both external and internalized

standards of conduct (Zahn-Waxler and Radke-Yarrow, 1990; Zahn-

Waxler et al., 1992). Compliance is dependent on the child’s ability to

control his reactions, as well as his motivation to do so.

Parents contribute in multiple ways to children’s developing capacity

for emotion regulation. As with the infant’s emerging ability to regulate

states like crying, the parents’ role in socializing emotion regulation is one

of gradually handing over the reins to the child. At first, parents and other

caregivers intervene directly to soothe or pacify the infant, organizing the

child’s experiences around routines that are manageable and predictable.

These behaviors lend predictability to the infant’s world, reduce the emo-

tional demands of daily experiences, and “scaffold” the infant’s own efforts

at emotion regulation. Later, parents and others coach children in strate-

gies for mobilizing their emotions to fit the needs of a given situation,

whether it involves comforting a hurt friend, learning to take turns, or

dealing with the

frustration of attempting a task that is just beyond their

capabilities (Thompson, 1990). This involves a subtle blend of give-and-

take with the child (i.e., you hide and learn that you can handle the anxiety

of doing without me momentarily, and then I’ll find you and dispel your

anxiety), the provision of supportive challenges (i.e., this puzzle may be a

little frustrating, but I’ll help you do it), and respect for the child’s unique

ways of dealing with emotions (i.e., I’ll let you blow off some steam before

I try to calm you down). Equally important, however, are the more subtle

ways in which the reassurance that young children derive from their attach-

ments to caregivers constitute an important resource for emotion regulation

(Cassidy, 1994, 1995; Cassidy and Berlin, 1994; Nachmias et al., 1996).

Emotion regulation is fostered, in other words, not only by the parent’s

immediate interventions but also by the security and confidence that the

relationship with the caregiver inspires in children as they grapple daily

with feelings that, initially without even a vocabulary to describe them let

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alone strategies for managing them, can be confusing and frightening (Case,

1992; Diamond, 1996; Diamond and Taylor, 1996; Diamond et al., 1994;

Johnson, M.H., 1998; Rothbart et al., 1990, 1994; Stuss, 1992).

Parents, however, do not operate in a vacuum. Research is revealing

the large extent to which the task of learning how to manage one’s emo-

tions and integrate them into daily life is a different challenge for children

with different temperaments, as well as for their parents. The ability to

inhibit a response one is all set to perform, sometimes called effortful

control, has been of special interest to researchers who seek to understand

how individual differences in children’s tendencies to respond to stressful or

exciting events affect the growth of emotion regulation. Effortful control is

one component of a larger set of inhibitory competencies, termed “execu-

tive functions,” discussed later in this chapter.

Effortful control is what enables the preschooler to take a response that

is “primed” and inhibit it. Examples include acting only when it is appro-

priate to the rules (such as when the game leader says “Green light!”),

constraining negative emotional outbursts, and planning a long-term strat-

egy for a desired reward (such as saving an allowance to buy a Nintendo

game). A game like Red Light, Green Light or Simon Says, for example,

involves getting one type of behavior going (like walking quickly to the

finish line or doing whatever Simon says as fast as you can) and then

suddenly inhibiting or stopping those actions. Doing well at these games

requires paying sharp attention for a long time, keeping track of the rules of

the game, and interrupting actions that you are all set to perform. The

more excited children get about playing these games, the harder it is for

them to play them well. The faster they get going, the harder it is to stop.

In the language used at the beginning of this chapter, the stronger the

reaction, the greater the challenge for regulation.

The ability to play these games (and to use these competencies in gen-

eral) seems to involve the development of structures in the prefrontal areas

of the brain (Rothbart et al., 1995). An area of the frontal lobe called the

anterior cingulate gyrus becomes very active any time one effortfully at-

tempts to inhibit a thought or action for which one is primed. This area of

the brain, like many areas in the frontal lobe, develops slowly over the

course of childhood. People get better at performing the cognitive tasks

that involve the anterior cingulate as they get older, and they also get better

at controlling their emotional expressions as they get older. What research-

ers are now trying to determine is whether these two phenomena go to-

gether. Children of the same age exhibit differences in behaviors that

should reflect the development of the frontal lobe. Parents and teachers

report that some children are better than others at inhibiting inappropriate

behavior, playing games like Red Light, Green Light and so on. So far, for

normally developing children, the most evidence that effortful control is

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involved in emotion regulation comes from studies using parent and teacher

questionnaires and observational tasks (i.e., not peeking while an experi-

menter wraps a present for you) involving behaviors that should reflect

these competencies. There is very little evidence as yet that relates data

obtained from these methods to activity in the anterior cingulate or other

areas in the frontal lobes. Thus, the link to brain development is still only

a theoretical one.

Children develop effortful control competencies gradually over the pre-

school years, and the full expression of these competencies requires devel-

opment that extends into adolescence. From early in their development,

some children seem to be better at effortful control than others, and there

appears to be reasonable stability in this aspect of temperament and regula-

tory capacity (Kochanska et al., 2000). There is also growing evidence that

individual differences in these capacities have meaningful implications for

several aspects of early development that parents and others who work

with young children care a great deal about. For example, young children

who are higher on measures of effortful control tend to perform better on

measures of early conscience and moral behavior (Kochanska et al., 1996,

1997). Conversely, infants and young children who have difficulties with

inhibiting more compelling, negative impulses also tend to elicit aversive

responses from others which, in turn, recreate precisely the kinds of experi-

ences that lead to impulsive and negative behaviors (Rothbart and Bates,

1998). Not surprisingly, children who are not good at effortful control

have a hard time with peer relations (see Chapter 7). In each of these

examples, the response biases that come with a young child’s unique tem-

peramental profile provide the intrinsic context within which developing

capacities for self-regulation emerge.

In sum, self-regulatory skills have important implications for how well

children negotiate many other tasks of early childhood. Identifying and

intervening with children who need extra help in developing these compe-

tencies may be important. However, determining who really needs help, as

opposed to just more time to grow up, may be difficult. Furthermore, it

seems possible that children who have more to regulate (i.e., those who are

more exuberant and more active, more anxious and inhibited) may appear

to be delayed or deficient in self-regulatory abilities, when in fact they are

not. They may simply need to reach more mature levels of these abilities to

be able to adequately manage who they are.

REGULATION OF ATTENTION AND EXECUTIVE FUNCTION

Just as infants and young children must learn to control their emotions,

they must also learn to control behavior and regulate mental processes.

The ability to think, retrieve, and remember information, solve problems,

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and engage in other complex symbolic activities involved in oral language,

reading, writing, mathematics, and social behavior is dependent on the

development of attention, memory, and executive function (Lyon, 1996).

Difficulties with these more cognitive

aspects of self-regulation can lead to

problems in school, in relationships, and in life.

Self-regulation of attention and cognitive abilities is often described as

a form of executive function. Executive function is an umbrella term used

to refer to a variety of interdependent skills that are necessary for purpose-

ful, goal-directed activity, such as learning to hold a crayon and scribble on

paper, string beads, or hand a cup of juice to a friend without spilling (e.g.,

Luria, 1966; Shallice, 1982). To engage in these sorts of behaviors, the

child must be able to deploy a series of relatively complex skills. They

include generating and maintaining an appropriate mental representation

that guides goal attainment (“I need to hold up the string and put the end

through the hole in the bead”), monitoring the flow of information about

one’s progress (“I’ve got one on, now I’ll try another”), and modifying and

flexibly adapting problem-solving strategies so that behavior is continually

directed toward the goal (“Oops, that bead was too hard to string; maybe

I need to find a bead with a bigger hole”). These skills are needed whether

the task involves correctly sorting colored blocks, gaining entry to a peer

group, or successfully riding a tricycle. The construct of executive function

is difficult to define, in part, because executive function, attention, and

memory are interdependent and have fuzzy boundaries (Lyon, 1996). De-

spite difficulty in establishing a clear definition, there is growing consensus

among researchers as to what executive functions entail: self-regulation,

sequencing of behavior, flexibility, response inhibition, planning, and orga-

nization of behavior (see Eslinger, 1996). Control and modulation of

behavior are fostered by the abilities to initiate, shift, inhibit, sustain, plan,

organize, and strategize (Denckla, 1989).

Emerging Capacities for Executive Functioning

Early researchers did not study executive functioning in young chil-

dren, believing that executive skills were not functional until the brain

reached maturity in adolescence (Golden, 1981). It is now generally recog-

nized that early precursors of these skills are present in infancy (Welsh and

Pennington, 1988), and there is a growing body of research that demon-

strates that performance on executive tasks improves in a stage-like manner

that coincides with growth spurts in frontal lobe development during in-

fancy and through the early childhood years (Anderson, 1998; Bell and

Fox, 1992, 1994; Levin et al., 1991; Posner et al., 1998; Thatcher, 1991;

Welsh and Pennington, 1988). This evidence for the early emergence of

executive skills is further supported by findings from the neuropsychologi-

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cal literature that link deficits in executive function to early frontal lobe

dysfunction (Benton, 1991; Eslinger and Grattan, 1991; Tranel et al., 1994).

What are the first signs of emerging executive skills, and when do they

develop? At a very basic level, executive functions cannot emerge before the

child is able to orient to relevant and important features in the environ-

ment, anticipate events, and represent the world symbolically (Barkley,

1996; Borkowski and Burke, 1996; Denckla, 1996; Pennington et al., 1996).

Recent methodological advances have made it possible to study some ele-

ments of these abilities in infants. For example, Haith and his colleagues

have demonstrated that infants as young as 6 weeks are capable of antici-

pating a sequence of events (Dougherty and Haith, 1997; Haith and

McCarty, 1990; Haith et al., 1988). When they are shown pictures that

appear and disappear in predictable locations at predictable times, 6-week-

old infants quickly form expectations and demonstrate they can anticipate

the location of the next picture by shifting their eyes to the predicted

location before the picture appears (Haith et al., 1988). The ability to make

anticipatory eye movements using these simple sequences improves with

age, becoming consistent by 3 1/2 to 4 months (Haith et al., 1988; Johnson

et al., 1991), but then it reaches a plateau in which there is no improvement

between 4 and 10 months (Posner et al., 1997). It is not until age 18

months that infants can anticipate ambiguous, context-dependent sequences

(e.g., learning to look at a target that moved from location 1 to location 2

and then back to locatoin 1 before moving to location 3) that would require

focused attention in adults (Posner et al., 1997). These emerging abilities to

control attention underlie the development of executive functions that en-

tail, for example, planning and executing sequences of behavior.

Means-ends behavior, another precursor to executive functioning, com-

monly emerges around ages 8 to 12 months, when the infant will, for

example, remove an obstacle to retrieve a toy (Piaget, 1952). Research

aimed at linking the emergence of goal-directed behavior to early brain

development has provided evidence that frontally mediated, goal-directed,

planful behavior is present as early as 12 months in infants (Diamond,

1988; Diamond and Goldman-Rakic, 1989; Goldman-Rakic, 1987). At

about the same time, children learn to use language and to represent the

world through symbols. Symbolic representation and language are the

means through which a child can link the present with past knowledge and

a future goal (e.g., Baron and Gioia, 1998; Kopp, 1997). They are believed

to be the cornerstone for working memory and a necessary component for

executive problem solving (Goldman-Rakic, 1987).

A third skill that emerges in infancy and continues to develop through

childhood is self-control (Kopp, 1982). Research on self-control examines

the child’s emerging ability to comply with a request, to inhibit or delay an

activity, and to monitor behavior according to the situational demands

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(Kopp, 1982). The ability to exercise self-control increases from 18 to 30

months and becomes more stable across time and across situations (Vaughn

et al., 1984).

The capacity to use developing executive function to regulate behavior

and emotions in the service of social goals and situational demands is

sometimes referred to as inhibitory or effortful control, as discussed above.

Because many skills, competencies, and experiences affect whether a child

can regulate his or her emotions and behavior, researchers have used a wide

variety of tasks to assess individual differences in effortful control. These

tasks include being able to shift with ease from doing something as “fast as

you can” to “as slow as you can” to being able to “not peek” when waiting

for a surprise gift, to being able to play games like Simons Says. When

individual differences on such tasks are assessed and averaged, they provide

one window into why some children comply more readily with adult re-

quests not to touch interesting things even when the parent is not watching

and more readily resist the temptation to cheat on games even when they

think they will not be caught. Being good at effortful control tasks, includ-

ing those that more directly assess executive functioning, doesn’t mean that

a child will behave in compliance with social rules that require self-control,

however. Aspects of children’s relations with others that motivate them to

want to adopt the rules of their group also matter (Kochanska, 1990).

A number of researchers have investigated the developmental trajecto-

ries of executive function by presenting children with a battery of tests

purported to measure different aspects of this domain of regulatory behav-

ior (e.g., Gnys and Willis,

1991; Levin et al., 1991; Welsh et al., 1991). The

focus here is not on precursors of executive function, but on manifestations

of behaviors that constitute components of this construct. These studies

have demonstrated that the different component skills involved in executive

functioning show different developmental trajectories and mature at differ-

ent rates. In one of the first studies to include preschoolers, children ages 3

to 12 were presented with a series of tasks that involved visual searching,

verbal fluency, motor planning, planning sequences, the ability to respond

flexibly to changes in the environment, and the capacity to inhibit responses

(Welsh et al., 1991). Patterns of performance on these measures indicated

that three underlying factors captured children’s responses: (1) fluid and

speeded response (2) hypothesis testing and impulse control and (3) plan-

ning. The investigators interpreted their findings as evidence for stage-like

development, with the first stage beginning around age 6, the next stage

around age 10, and the final stage during adolescence. Six-year-olds, for

example, were able to perform as well as adults on tasks that involved

visual searching and planning simple sequences, whereas it was not until

adolescence that the ability to plan complex sequences, verbal fluency, and

motor planning reached maturity.

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In contrast to the research on children’s emerging capacities to regulate

states and emotions, relatively little is known about how parents, other

adults, and features of children’s early environments affect the development

of attention regulation and emerging executive functions. These influences

clearly matter (Carlson et al., 1995), but researchers have yet to identify the

mechanisms that account for individual differences among young children.

Research on school-age children demonstrating that it is possible to teach

attentional skills and executive functions to individuals with developmental

disabilities (Borkowski and Burke, 1996; Graham and Harris, 1996) also

indicates that they are amenable to environmental influence.

Deficits in Executive Function and Attention

The importance of understanding how children learn to plan and orga-

nize new actions, remember past experiences and bring them to bear on

new experiences, and maintain attention to tasks is underscored by the

consistent relation of deficits in any one of these processes to problems in

school (Lyon, 1996). Of great interest to educators and parents alike is

growing evidence that deficits in attention regulation and behavioral con-

trol are integral to disorders such as attention deficit hyperactivity disorder

(ADHD). They also have vast implications for social and emotional behav-

ior given the highly permeable boundaries between cognitive abilities and

social competence. For example, forethought and planning are intimately

involved in making friends, seeking attention, and solving interpersonal

conflicts. Because social interactions involve people and people are often

unpredictable and have their own goals that may interfere with one’s own,

flexibility is essential for achieving social goals (Goodnow, 1987). To be a

competent social problem solver, one must be able to detect obstacles that

will interfere with social goals, generate and evaluate alternative strategies

to overcome or prevent these obstacles, and be able to flexibly adapt behav-

ior to meet the challenges presented by the constantly changing social envi-

ronment (Rubin and Krasnor, 1986). These are extremely challenging

tasks for young children.

Designing appropriate, individualized interventions for young children

who are displaying early deficits in organizational, planning, and attention-

related capacities depends on understanding the processes that underlie

their development and manifestation. Taking ADHD as an example, this is

generally considered to be a relatively common disorder, with prevalence

estimates ranging from 0 to 16.7 percent with a median of 2 percent for

school-age children (Lahey et al., 1999). Yet the true prevalence and the

cause of ADHD remain unknown (Zametkin and Ernst, 1999). According

to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV;

American Psychiatric Association, 1994), the diagnosis of ADHD requires

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evidence of either inattention or hyperactivity and impulsivity. There are

three subtypes of ADHD, the predominantly hyperactive-impulsive type,

the predominantly inattentive type, and the combined type. Most of the

research to date is on the hyperactive-impulsive and combined types. Fo-

cus on the inattentive subtype is an emerging research topic.

Tests of the validity of the three DSM-IV subtests of AHDH for pre-

schoolers have been conducted with children 4 to 6 years of age. The

findings show that the subtests are valid for children of these ages (Lahey et

al., 1998). Yet diagnosis is complicated by the fact that many of the

behaviors associated with ADHD are normal for preschoolers who often

have difficulty paying attention and are impulsive and fidgety by nature.

And there is no information about the validity of ADHD diagnosis below

age 4. The absence of a nationally representative epidemiological study of

mental health problems in the childhood population leaves us in the dark

with regard to efforts to distinguish children who are at the ends of a typical

spectrum from those who are manifesting serious delays. A related critical

issue in both research and practice concerns how to differentiate ADHD

from other frequently coexisting conditions, such as learning disabilities,

oppositional-defiant disorder, conduct disorders, and anxiety disorders and

also how to individualize treatment when ADHD occurs in conjunction

with these and other disorders. A recent study of 7- to 9-year-old children

shows that different types of treatments for ADHD benefit individuals with

different combinations of problems (MTA Cooperative Group, 1999). Fi-

nally, recalling the core concepts in Chapter 1, it is critically important to

note that many of the symptoms of ADHD are also nonspecific indicators

that something is not quite right. Heightened activity can also occur, for

example, when a child is overly tired or upset. This can make the clinician’s

task of sorting out true disorder from other problems exceedingly difficult,

perhaps especially with a diffusely defined disorder such as ADHD (Rutter

and Sroufe, in press).

In sum, understanding the constructs of attention, memory, and execu-

tive function is critical for understanding how children think, learn, and

develop. Because these constructs are hard to define and have overlapping

boundaries, there is a pressing need to develop more refined definitions of

executive function and its component skills, and for valid measures of early

manifestations of pertinent behaviors and abilities (Weinberg et al., 1996).

The capacity to map specific executive functions onto specific areas of the

brain and to distinguish normal development from emerging disorders is

dependent on such efforts to lend greater precision to the analysis of task

demands and individual children’s responses. For these important capaci-

ties, there is much to learn about the emergence, integration, and consolida-

tion of the skills that serve as building blocks for adaptive behavior and

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provide a yardstick against which to evaluate

what is abnormal neurologi-

cal or cognitive development.

It is clear at this point that the various components of active, internally

guided regulation of attention, behavior, and emotion emerge in intricately

interrelated ways at the end of the first year of life and then develop more

rapidly during the toddler and preschool years (Kopp, 1982; Rothbart and

Bates, 1998). They emerge in the context of caregiving relationships that

explicitly guide the child from her dependence on adults to regulate virtu-

ally every aspect of functioning to gradually taking over and self-regulat-

ing her own behaviors and feelings in one aspect of her life after another.

Parents don’t tell their 3-year-olds to clean up their rooms and then leave

them to their own devices. They help by suggesting that they start with the

clothes and throw them in the hamper and then put away their blocks on

the shelf. They praise them at each step along the way and then move on

to pulling the covers up on the bed. They repeat these patterns over and

over, day after day, and then begin to pull back the scaffolding as the child

begins to do it himself. Some children need more scaffolding than others

and for longer times. Some children have serious disorders, such as mental

retardation, that interfere with their ability to benefit from parents’ and

others’ efforts to help them practice and then extend their emerging com-

petencies. Sorting out children who don’t have sufficient help from those

with serious disorders is extremely challenging. In attempting to distin-

guish normal development from emerging disorders in these regulatory

domains, it is crucially important to consider the contexts within which

children’s executive functioning and self-regulatory behaviors have been

struggling to develop.

SUMMARY AND CONCLUSIONS

The capacity for self-regulation, ranging from sleeping and settling in

the earliest weeks of life to the preschooler’s emerging capacity to manage

emotions, inhibit behavior, and focus attention on important tasks, reflects

young children’s transition from helplessness to competence. Stated sim-

ply, early development entails the gradual transition from extreme depen-

dence on others to manage the world for us to acquiring the competencies

needed to manage the world for oneself. Research on this transition has

focused on the triad of regulatory tasks captured by emotion regulation,

behavior regulation, and attention regulation. In reality, however, these

dimensions of self-regulation are highly interrelated. Success in one area

can fuel success in another; problems in one area can undermine develop-

ment in another. There is much to learn about normative patterns of

regulatory development, as well as the adjustments made by young children

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122 FROM NEURONS TO NEIGHBORHOODS

with a range of developmental disabilities, and the mechanisms that under-

lie the successful navigation of the many challenges encountered en route to

well-regulated behavior.

Regulation in early development is deeply embedded in the child’s

relations with others. Providing the experiences, supports, and encourage-

ment that enable children to take over and self-regulate in one area of

functioning after another is one of the most critical elements of good

caregiving. Indeed, the locus of regulatory problems during the early

months of life is increasingly seen as residing not in the infant’s behavior

(e.g., excessive crying, irregular sleeping) but in the transactions that tran-

spire between infants and their caregivers and the more enduring percep-

tions and patterns of interaction that are subsequently set in motion in the

family. These transactions, in turn, provide a promising entry point for

early interventions aimed at getting new parents and their infants off to a

good start.

There is also growing appreciation of the fact that learning to regulate

one’s emotions, behaviors, and task-oriented capacities is a different chal-

lenge for children with different temperaments, for children with a variety

of diagnosed disabilities, and for their caregivers. While overly active and

disinhibited children often come to the attention of adults, those who fall at

the other end of the spectrum all too often are overlooked.

Recent attention to problematic regulatory behavior has, in fact, been

prompted by growing concern about early precursors of conduct problems,

attention deficits, depressive and anxiety disorders, and other psychological

problems of childhood. While emerging evidence suggests that regulatory

problems can offer early warning signs, there are many pitfalls on the road

to early diagnosis. Virtually all young children display “poorly regulated”

behavior simply as part of being a little kid. Children with temperaments

that give them more to regulate can appear to be deficient in self-regulatory

abilities when, in fact, they are not. In this context, identifying and inter-

vening with children who need extra help is fraught with ambiguity and

runs the risk of overdiagnosis and unnecessary treatment.

Nevertheless, some young children are struggling with serious mental

health problems and need help urgently. These issues were highlighted

recently by the Surgeon General’s report on mental health (U.S. Depart-

ment of Health and Human Services, 1999b), which includes an extensive

discussion of children’s vulnerability to mental health problems, the impor-

tance of understanding these problems in the context of children’s social

environments, and the nation’s serious personnel shortages that constrain

the capacity to address them. Recent reports of extensive use of pharmaco-

logical treatments for preschoolers with behavioral disorders (Zito et al.,

2000) have raised urgent questions about how best to address social and

emotional problems in young children and further highlight how poorly

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equipped the nation is to respond to these issues. For children whose

problems do not fall within the clinical range, early interventions to address

regulatory behavior focused on “fixing” the environment to reduce de-

mands on the child warrant serious attention to balance the current focus

on “fixing” the child. It is also clear that focusing on young children’s

relationships with adults and peers is a promising and complementary, yet

poorly exploited, approach.

Finally, cultural dimensions of regulatory development have been ne-

glected by most scientists and practitioners alike. Nevertheless, cultural

values have a profound impact on how young children learn to interpret

and express their emotions, and on the behaviors that are seen as appropri-

ate in different circ*mstances. Cultural expectations about self-regulatory

behavior can even affect the boundaries of what is considered “childhood.”

The Yoruba, for example, define childhood in terms of self-reliance and no

longer refer to children who can talk, walk, dress themselves, and do cer-

tain other things around the house as children (Zeitlin, 1996). These

cultural dimensions have important yet unexplored implications for chil-

dren whose home culture is not the same as the dominant culture in other

settings they inhabit (e.g., child care, homes of friends, intervention pro-

grams) and for adults who work with diverse groups of young children and

whose responses to their behaviors are highly contingent on their own

cultural expectations.

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124

Communicating and

Learning

hrough the early childhood years, emerging

com-

munication skills and capacities for learning support

other critical developments. The infant who learns more readily to replace

crying with rudimentary attempts at other forms of communication (e.g.,

pointing and directing her gaze) spends more time in happier states and is

an easier baby for parents to manage during the early months of life

(Crockenberg, 1981). Preschoolers who speak clearly and communicate

their ideas more effectively are better able to sustain bouts of play with

other children (Guralnick et al., 1996). Even before children enter school,

weak academic skills are associated with, and over time appear to exacer-

bate, behavioral and attention problems (Arnold, 1997; Hinshaw, 1992;

Morrison et al., 1989). This is not to say that efforts to support language

and cognitive development or to remediate delays in speech, hearing, and

learning, will fix all other early developmental problems. Rather, without

attention to problems in these domains of development, important and

sometimes powerfully influential avenues to addressing emotional and be-

havioral problems may be neglected. Scientists are, however, only begin-

ning to understand how these intersecting strands of development operate

to either foster or undermine development as a whole during the early years

of life.

The young child’s growing skills in communication, language, and

learning are also vitally important in their own right. No one disputes that

success and persistence in school are major contributors to constructive life

pathways (Stipek, in press). Children who do not complete high school, for

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COMMUNICATING AND LEARNING 125

example, are significantly more likely as adults to display a host of behav-

iors that are destructive to themselves and others, including substance abuse,

unemployment, low income, welfare dependency, delinquency, and crime

(Haveman and Wolfe, 1984; Hawkins and Lishner, 1987; Hinshaw, 1992;

Loeber and Stouthamer-Loeber, 1987; Rutter et al., 1998; Steinberg et al.,

1984).

One of the most significant insights about educational attainment in

recent years is that educational outcomes in adolescence and even beyond

can be traced back to academic skills at school entry (Chen et al., 1996;

Cunningham and Stanovich, 1997; Luster and McAdoo, 1996; Weller et

al., 1992). Academic skills at school entry can, in turn, be traced to capa-

bilities seen during the preschool years and the experiences in and out of the

home that foster their development. Children’s cognitive skills before they

enter kindergarten show strong associations with achievement in elemen-

tary and high school (Hess and Hahn, 1974; Stevenson and Newman,

1986) and during early adulthood (Baydar et al., 1993). Preschool general

cognitive ability has also been shown to predict high school completion

(Brooks-Gunn et al., 1993). This evidence underpins the national commit-

ment to school readiness and has fueled the proliferation of public pre-

kindergarten programs (Schulman et al., 1999).

It is important to note that children who start school lagging behind

their peers in language and cognitive abilities are not doomed to be school

failures and dropouts. To the contrary, early interventions can make sub-

stantial contributions to the academic skills of young children (see Chapter

13). Moreover, the associations found between early and later achievement

leave substantial unexplained variance. This means that there is plenty of

room for children to defy the odds, and many do.

Both language development and the emergence of early learning capa-

bilities appear to be relatively resilient processes. This means that they are

relatively protected from adverse circ*mstances, that it may take more to

undermine these processes than is the case for other aspects of develop-

ment, and that they can show surprising recovery if children exhibiting

delays are placed in more advantageous environments. Nevertheless, some

aspects of language and cognition appear to be less resilient and more open

to environmental influence than others, including vocabulary and

attentional capacities. These aspects are particularly important to school

success, in part because of what they can set in motion once a child enters

formal schooling. They are also characterized by striking socioeconomic

differences and therefore contribute to inequities in children’s life chances.

Moreover, the prospects for children with serious delays in language and

cognition resulting from developmental disabilities and specific disorders

can be seriously constrained and are heavily dependent on early detection

and intervention. This chapter illustrates these points first with a discussion

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126 FROM NEURONS TO NEIGHBORHOODS

of what is now known about the development of communication and lan-

guage, and then with a discussion of how children learn about the world

and come to view themselves as competent individuals.

LANGUAGE ACQUISITION AND COMMUNICATION

Starting from the first day of life, the development of communication

skills, language, and literacy are significant accomplishments. The child’s

first word is a cause for celebration. Parents watch in amazement as these

words multiply exponentially, turn into phrases and then sentences, and

ultimately allow them to have almost adult like conversations with their

preschoolers. The transition from a newborn who can barely keep his eyes

focused on a book to a preschooler who laughs and cries when his parent

reads or tells a story, moves his fingers along a page and pretends to read,

and, in some cases, can read himself is equally impressive. Almost all chil-

dren learn to talk without explicit instruction, suggesting that language

acquisition is a relatively resilient process, although they do not all learn to

talk well, suggesting that language acquisition includes some more fragile

elements. In contrast, reading as a component of literacy is a much more

fragile process. Not everyone achieves fluent reading, and instruction seems

to be essential. Indeed, some cultures don’t even have a written system. The

development of reading is addressed in a pair of recent reports from the

National Research Council: Preventing Reading Difficulties in Young Chil-

dren (National Research Council, 1998a) is written primarily for a research

audience, and Starting Out Right (National Research Council, 1998b) is

geared to parents and practitioners.

Only recently has information about trends in young children’s literacy

development become available, and the data span only 6 years (Nord et al.,

1999). Unfortunately, the information comes exclusively from parent re-

ports, which can contain biases, but the sample is nationally representative.

They tell us that 3- to 5-year-olds in 1999 have somewhat better knowledge

of the alphabet and are able to count a bit higher (i.e., 57 versus 52 percent

in 1993 can count to 20 or higher) than their counterparts in 1993, but they

are no more likely to be able to write their own names or to read or pretend

to read. Moreover, the majority of the statistically significant changes are

for children who are less at risk of school failure, namely, those who are not

poor and whose mothers speak English. The somewhat good overall news

must thus be tempered by the fact that the children for whom we most want

to see progress are still being left behind. In this discussion, we do not

attempt to recount all of the accomplishments of young children in the

realm of literacy; rather, we focus on the ways in which (and for whom)

language development is and is not resilient, the role of the environment—

particularly that provided by the parent—and implications for intervention.

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of critical role “behind the scenes”

that ensures a successful project. We remain deeply grateful for their excep-

tional level of support.

Jack P. Shonkoff, Chair

Deborah A. Phillips, Study Director

Committee on Integrating the Science of

Early Childhood Development

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Contents

EXECUTIVE SUMMARY 1

I SETTING THE STAGE

1 Introduction 19

2 Rethinking Nature and Nurture 39

3 The Challenge of Studying Culture 57

4 Making Causal Connections 70

II THE NATURE AND TASKS OF EARLY DEVELOPMENT

5 Acquiring Self-Regulation 93

6 Communicating and Learning 124

7 Making Friends and Getting Along with Peers 163

8 The Developing Brain 182

III THE CONTEXT FOR EARLY DEVELOPMENT

9 Nurturing Relationships 225

10 Family Resources 267

11 Growing Up in Child Care 297

12 Neighborhood and Community 328

13 Promoting Healthy Development Through Intervention 337

xvii

219

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IV KNOWLEDGE INTO ACTION 381

14 Conclusions and Recommendations 383

References 417

APPENDIXES

A Related Reports from the National Academies 535

B Defining and Estimating Causal Effects 545

C Technologies for Studying the Developing Human Brain 549

D Biographical Sketches 553

Index 561

xviii CONTENTS

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From Neurons

to Neighborhoods

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From Neurons to Neighborhoods: The Science of Early Childhood Development

Executive Summary

cientists have had a long-standing fascination with

the complexities of the process of human develop-

ment. Parents have always been captivated by the

rapid growth and development that characterize the earliest years of their

children’s lives. Professional service providers continue to search for new

knowledge to inform their work. Consequently, one of the distinctive fea-

tures of the science of early childhood development is the extent to which it

evolves under the anxious and eager eyes of millions of families, policy

makers, and service providers who seek authoritative guidance as they

address the challenges of promoting the health and well-being of young

children.

PUTTING THE STUDY IN CONTEXT

Two profound changes over the past several decades have coincided to

produce a dramatically altered landscape for early childhood policy, service

delivery, and childrearing in the United States. First, an explosion of re-

search in the neurobiological, behavioral, and social sciences has led to

major advances in understanding the conditions that influence whether

children get off to a promising or a worrisome start in life. These scientific

gains have generated a much deeper appreciation of: (1) the importance of

early life experiences, as well as the inseparable and highly interactive in-

fluences of genetics and environment, on the development of the brain and

the unfolding of human behavior; (2) the central role of early relationships

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2 FROM NEURONS TO NEIGHBORHOODS

as a source of either support and adaptation or risk and dysfunction; (3) the

powerful capabilities, complex emotions, and essential social skills that

develop during the earliest years of life, and (4) the capacity to increase the

odds of favorable developmental outcomes through planned interventions.

Second, the capacity to use this knowledge constructively has been

constrained by a number of dramatic transformations in the social and

economic circ*mstances under which families with young children are liv-

ing in the United States: (1) marked changes in the nature, schedule, and

amount of work engaged in by parents of young children and greater

difficulty balancing workplace and family responsibilities for parents at all

income levels; (2) continuing high levels of economic hardship among fami-

lies, despite overall increases in maternal education, increased rates of par-

ent employment, and a strong economy; (3) increasing cultural diversity

and the persistence of significant racial and ethnic disparities in health and

developmental outcomes; 4) growing numbers of young children spending

considerable time in child care settings of highly variable quality, starting in

infancy; and (5) greater awareness of the negative effects of stress on young

children, particularly as a result of serious family problems and adverse

community conditions that are detrimental to child well-being. While any

given child may be affected by only one or two of these changes, their

cumulative effects on the 24 million infants, toddlers, and preschoolers who

are now growing up in the United States warrant dedicated attention and

thoughtful response.

This convergence of advancing knowledge and changing circ*mstances

calls for a fundamental reexamination of the nation’s responses to the needs

of young children and their families, many of which were formulated sev-

eral decades ago and revised only incrementally since then. It demands that

scientists, policy makers, business and community leaders, practitioners,

and parents work together to identify and sustain policies and practices that

are effective, generate new strategies to replace those that are not achieving

their objectives, and consider new approaches to address new goals as

needed. It is the strong conviction of this committee that the nation has not

capitalized sufficiently on the knowledge that has been gained from nearly

half a century of considerable public investment in research on children

from birth to age 5. In many respects, we have barely begun to use our

growing research capabilities to help children and families negotiate the

changing demands and possibilities of life in the 21st century.

THE COMMITTEE’S CHARGE

The Committee on Integrating the Science of Early Childhood Develop-

ment was established by the Board on Children, Youth, and Families of the

National Research Council and the Institute of Medicine to update scien-

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EXECUTIVE SUMMARY 3

tific knowledge about the nature of early development and the role of early

experiences, to disentangle such knowledge from erroneous popular beliefs

or misunderstandings, and to discuss the implications of this knowledge

base for early childhood policy, practice, professional development, and

research.

The body of research that the committee reviewed is extensive, multi-

disciplinary, and more complex than current discourse would lead one to

believe. It covers the period from before birth until the first day of kinder-

garten. It includes efforts to understand how early experience affects all

aspects of development—from the neural circuitry of the maturing brain, to

the expanding network of a child’s social relationships, to both the endur-

ing and the changing cultural values of the society in which parents raise

children. It includes efforts to understand the typical trajectories of early

childhood, as well as the atypical developmental

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To study the process of language learning, the most common technique

is to do nothing more than observe children as they talk. Early studies

consisted of diaries that researcher parents made of their own child’s first

utterances. The goal was to write down all of the new utterances that the

child produced. Diary studies were later replaced by audio and video

samples of talk from a number of children, usually over a period of years.

The most famous of these studies is Roger Brown’s longitudinal observa-

tions of Adam, Eve, and Sarah (Brown, 1973). Because transcribing and

analyzing child talk is so labor-intensive, language acquisition studies typi-

cally focus on a small number of children, often interacting with their

primary caregiver at home. Naturalistic observations of children’s talk can

be supplemented with experimental probes that are used with larger num-

bers of children. For example, Berko (1958) gave children nonsense words

and asked them to generate novel forms in different contexts (e.g., “This is

a wug. Now there are two of them. There are two ____?” The child who

understands English plurals should supply the word “wugs”). Unlike many

areas of developmental research, language acquisition studies have been

conducted across the globe, although typically the studies focus on a small

number of children in each culture (see Slobin, 1985).

Language Learning is a Resilient Process

Language learning turns out to be remarkably similar across cultures.

Children exposed to markedly different languages follow similar develop-

mental trajectories as they learn their native language. Six-month-old in-

fants can distinguish the full range of sounds used in the world’s languages,

but by age 1 they have lost many of these distinctions as they focus in on

their own culture’s language. Children the world over produce their first

words between 10 and 15 months (“mine,” “shoe”); they then learn that

the word can be composed of smaller, meaningful parts (morphology,

e.g.,“shoe” + “s”) and that the word is a building block for larger, mean-

ingful phrases and sentences (syntax, e.g., “my shoe”). Most 18-month-

olds have begun a word-learning explosion, acquiring (on average) 9 new

words a day, every day, throughout the preschool years (Carey, 1978).

They also begin to produce two-word strings that are highly similar across

languages in two respects. First, the content is the same. Children note the

appearance and disappearance of objects, their properties, locations, and

owners and comment on the actions done to and by objects and people.

Second, the words in these short sentences are consistently ordered in ways

that mirror adult word orders (e.g., “drink juice,” “Mommy give”).

By the time children are 3 years old, full sentences are the norm (“I wish

I could sit on a horse and ride him to every house in the world”; Hoff-

Ginsberg, 1997). These sentences often involve elaborating one element of

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128 FROM NEURONS TO NEIGHBORHOODS

a single proposition (“baby drinking big bottle”) or combining two propo-

sitions with a conjunction (“maybe you can carry that and I can carry

this”). Three-year-olds can also show some remarkably subtle capabilities

for language comprehension. For example, consider a child who is told that

a little girl fell and ripped her dress in the afternoon and reported the event

to her mother later that night. When 3-year-olds are asked, “When did the

girl say she ripped her dress?” they will provide one of two possible answers

(in the afternoon, or at night), but when asked “When did the girl say how

she ripped her dress?” they will provide only one (at night). By age 4 or 5,

children all over the world have mastered the fundamental (and many of

the fine points) of the grammatical system of their native language, includ-

ing verb declensions, gender agreement, embedded clauses, and the like

(Brown, 1973; Slobin, 1985).

This common trajectory of language acquisition is particularly striking

given the variability in input that children receive across cultures. In all

cultures, language is one of the most powerful symbolic systems through

which children learn to understand and interpret human behavior

(Harwood et al., 1995). How language is used in the context of social

interaction is just as important as what is said. For example, in some

cultures, children are commonly spoken to directly as participants in con-

versation; in other cultures, children primarily overhear talk that is directed

toward others. Despite large differences of this sort, children proceed quite

uniformly with the task of language learning (Ochs and Schieffelin, 1984).

Another example is cross-cultural research on narrative constructions,

which reveals both considerable overlap across cultures in the narratives

that caregivers use with their children and also striking differences that

have an impact on the child. For example, Taiwanese mothers tend to tell

narratives that make explicit reference to moral rules and point out the

child’s wrongdoing. European-American mothers, by contrast, emphasize

the entertainment function over the didactic function and go to great lengths

to portray the child in a positive light (Miller et al., 1996). Children who

hear stories of this sort not only learn how to build their own culturally

appropriate narratives, but they also learn the social value of their behav-

iors, as noted in Chapter 7.

Language learning proceeds apace even when the child is faced with

learning two languages simultaneously (de Houwer, 1995; Hakuta, 1986;

National Research Council and Institute of Medicine, 1997). Children be-

coming bilingual from birth are not dramatically slowed in their develop-

ment and appear to develop each language as they would had it been their

only tongue. The problematic issue in the case of bi- or multilingualism is

less one of language acquisition than of language retention, which can be

made difficult when one language is not used or valued by nonfamily adults

or institutions, such as the schools, peer groups, and the broader society

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COMMUNICATING AND LEARNING 129

(National Research Council and Institute of Medicine, 1997, 1998b). For

example, language loss (of Spanish) among Mexican-American children

increases rapidly across first-, second-, and third-generation children

(Hakuta and D’Andrea, 1992). Finally, although language development is

markedly delayed among children raised in low-stimulating orphanages

(Rutter, 1981a), once placed in supportive families, children develop lan-

guage even with the added challenge, in most of the cases that have been

studied, of learning a new language.

Thus, language learning is apparently a very robust process. Where

does this robustness come from? One way to address this question is to

systematically vary either the learner or the learning environment, observ-

ing the effects of these variations on subsequent language development. As

an example from another species, Marler raised two closely related but

genetically distinct varieties of sparrows from the egg in identical environ-

ments, exposing them to a common collection of songs typical for both

(Marler, 1990). He found that the two varieties learned different songs out

of the same collection, each variety apparently zeroing in on different as-

pects of the input. The range of possible outcomes in the learning process,

for this species and for this skill, appears to have been narrowed by the

organism itself.

For obvious ethical reasons, researchers cannot deliberately

treatment, and ultimate prevention of serious childhood mental health prob-

lems.

Early Environments Matter and Nurturing Relationships Are Essential

The scientific evidence on the significant developmental impacts of

early experiences, caregiving relationships, and environmental threats is

incontrovertible. Virtually every aspect of early human development, from

the brain’s evolving circuitry to the child’s capacity for empathy, is affected

by the environments and experiences that are encountered in a cumulative

fashion, beginning early in the prenatal period and extending throughout

the early childhood years. The science of early development is also clear

about the specific importance of parenting and of regular caregiving rela-

tionships more generally. The question today is not whether early experi-

ence matters, but rather how early experiences shape individual develop-

ment and contribute to children’s continued movement along positive

pathways.

Conclusions

• The long-standing debate about the importance of nature versus

nurture, considered as independent influences, is overly simplistic and sci-

entifically obsolete. Scientists have shifted their focus to take account of the

fact that genetic and environmental influences work together in dynamic

ways over the course of development. At any time, both are sources of

human potential and growth as well as risk and dysfunction. Both geneti-

cally determined characteristics and those that are highly affected by expe-

rience are open to intervention. The most important questions now con-

cern how environments influence the expression of genes and how genetic

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EXECUTIVE SUMMARY 7

makeup, combined with children’s previous experiences, affects their on-

going interactions with their environments during the early years and

beyond.

• Parents and other regular caregivers in children’s lives are “active

ingredients” of environmental influence during the early childhood period.

Children grow and thrive in the context of close and dependable relation-

ships that provide love and nurturance, security, responsive interaction,

and encouragement for exploration. Without at least one such relationship,

development is disrupted and the consequences can be severe and long-

lasting. If provided or restored, however, a sensitive caregiving relationship

can foster remarkable recovery.

• Children’s early development depends on the health and well-being

of their parents. Yet the daily experiences of a significant number of young

children are burdened by untreated mental health problems in their fami-

lies, recurrent exposure to family violence, and the psychological fallout

from living in a demoralized and violent neighborhood. Circ*mstances

characterized by multiple, interrelated, and cumulative risk factors impose

particularly heavy developmental burdens during early childhood and are

the most likely to incur substantial costs to both the individual and society

in the future.

• The time is long overdue for society to recognize the significance of

out-of-home relationships for young children, to esteem those who care for

them when their parents are not available, and to compensate them ad-

equately as a means of supporting stability and quality in these relation-

ships for all children, regardless of their family’s income and irrespective of

their developmental needs.

• Early experiences clearly affect the development of the brain. Yet the

recent focus on “zero to three” as a critical or particularly sensitive period

is highly problematic, not because this isn’t an important period for the

developing brain, but simply because the disproportionate attention to the

period from birth to 3 years begins too late and ends too soon.

• Abundant evidence from the behavioral and the neurobiological sci-

ences has documented a wide range of environmental threats to the devel-

oping central nervous system. These include poor nutrition, specific infec-

tions, environmental toxins, and drug exposures, beginning early in the

prenatal period, as well as chronic stress stemming from abuse or neglect

throughout the early childhood years and beyond.

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8 FROM NEURONS TO NEIGHBORHOODS

Recommendations

• Recommendation 4 — Decision makers at all levels of government,

as well as leaders from the business community, should ensure that better

public and private policies provide parents with viable choices about how

to allocate responsibility for child care during the early years of their

children’s lives. During infancy, there is a pressing need to strike a better

balance between options that support parents to care for their infants at

home and those that provide affordable, quality child care that enables

them to work or go to school. This calls for expanding coverage of the

Family and Medical Leave Act to all working parents, pursuing the com-

plex issue of income protection, lengthening the exemption period before

states require parents of infants to work as part of welfare reform, and

enhancing parents’ opportunities to choose from among a range of child

care settings that offer the stable, sensitive, and linguistically rich caregiving

that fosters positive early childhood development.

• Recommendation 5 — Environmental protection, reproductive

health services, and early intervention efforts should be substantially ex-

panded to reduce documented risks that arise from harmful prenatal and

early postnatal neurotoxic exposures, as well as from seriously disrupted

early relationships due to chronic mental health problems, substance abuse,

and violence in families. The magnitude of these initiatives should be com-

parable to the attention and resources that have been dedicated to crime

prevention, smoking cessation, and the reduction of teen pregnancy. They

will require the participation of multiple societal sectors (e.g., private, pub-

lic, and philanthropic) and the development of multiple strategies.

• Recommendation 6 — The major funding sources for child care and

early childhood education should set aside a dedicated portion of funds to

support initiatives that jointly improve the qualifications and increase the

compensation and benefits routinely provided to children’s nonparental

caregivers. These initiatives can be built on the successful experience of the

U.S. Department of Defense.

Society Is Changing and the Needs of Young Children

Are Not Being Addressed

Profound social and economic transformations are posing serious chal-

lenges to the efforts of parents and others to strike a healthy balance be-

tween spending time with their children, securing their economic needs, and

protecting them from the many risks beyond the home that may have an

adverse impact on their health and development.

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EXECUTIVE SUMMARY 9

Conclusions

• Changing parental work patterns are transforming family life. Grow-

ing numbers of young children are being raised by working parents whose

earnings are inadequate to lift their families out of poverty, whose work

entails long and nonstandard hours, and whose economic needs require an

early return to work after the birth of a baby. The consequences of the

changing context of parental employment for young children are likely to

hinge on how it affects the parenting they receive and the quality of the

caregiving they experience when they are not with their parents.

• The developmental effects of child care depend on its safety, the

opportunities it provides for nurturing and stable relationships, and its

provision of linguistically

and cognitively rich environments. Yet the child

care that is available in the United States today is highly fragmented and

characterized by marked variation in quality, ranging from rich, growth-

promoting experiences to unstimulating, highly unstable, and sometimes

dangerous settings. The burden of poor quality and limited choice rests

most heavily on low-income, working families whose financial resources

are too high to qualify for subsidies yet too low to afford quality care.

• Young children are the poorest members of society and are more

likely to be poor today than they were 25 years ago. Growing up in poverty

greatly increases the probability that a child will be exposed to environ-

ments and experiences that impose significant burdens on his or her well-

being, thereby shifting the odds toward more adverse developmental out-

comes. Poverty during the early childhood period may be more damaging

than poverty experienced at later ages, particularly with respect to eventual

academic attainment. The dual risk of poverty experienced simultaneously

in the family and in the surrounding neighborhood, which affects minority

children to a much greater extent than other children, increases young

children’s vulnerability to adverse consequences.

Recommendations

The challenges that arise at the juxtaposition of work, income, and the

care of children reflect some of the most complex problems of contempo-

rary society. Rather than offer recommendations for specific actions, many

of which have been made before and gone unheeded, the committee wishes

to underscore the compelling need for a focused, integrative, and compre-

hensive reassessment of our nation’s child care and income support policies.

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10 FROM NEURONS TO NEIGHBORHOODS

• Recommendation 7 — The President should establish a joint federal-

state-local task force charged with reviewing the entire portfolio of public

investments in child care and early education. Its goal should be to develop

a blueprint for locally responsive systems of early care and education for

the coming decade that will ensure the following priorities: (1) that young

children’s needs are met through sustained relationships with qualified

caregivers, (2) that the special needs of children with developmental dis-

abilities or chronic health conditions are addressed, and (3) that the settings

in which children spend their time are safe, stimulating, and compatible

with the values and priorities of their families.

• Recommendation 8 — The President’s Council of Economic Advis-

ers and the Congress should assess the nation’s tax, wage, and income

support policies with regard to their adequacy in ensuring that no child

who is supported by the equivalent of a full-time working adult lives in

poverty and that no family suffers from deep and persistent poverty, re-

gardless of employment status. The product of this effort should be a set of

policy alternatives that would move the nation toward achieving these

fundamental goals.

Interactions Among Early Childhood Science, Policy, and Practice Are

Problematic and Demand Dramatic Rethinking

Policies and programs aimed at improving the life chances of young

children come in many varieties. Some are home based and others are

delivered in centers. Some focus on children alone or in groups, and others

work primarily with parents. A variety of services have been designed to

address the needs of young children whose future prospects are threatened

by socioeconomic disadvantages, family disruptions, and diagnosed dis-

abilities. They all share a belief that early childhood development is suscep-

tible to environmental influences and that wise public investments in young

children can increase the odds of favorable developmental outcomes. The

scientific evidence resoundingly supports these premises.

Conclusions

• The overarching question of whether we can intervene successfully

in young children’s lives has been answered in the affirmative and should be

put to rest. However, interventions that work are rarely simple, inexpen-

sive, or easy to implement. The critical agenda for early childhood inter-

vention is to advance understanding of what it takes to improve the odds of

positive outcomes for the nation’s most vulnerable young children and to

determine the most cost-effective strategies for achieving well-defined goals.

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EXECUTIVE SUMMARY 11

• The scientific knowledge base guiding early childhood policies and

programs is seriously constrained by the relatively limited availability of

systematic and rigorous evaluations of program implementation; gaps in

the documentation of causal relations between specific interventions and

specific outcomes and of the underlying mechanisms of change; and infre-

quent assessments of program costs and benefits.

• Model early childhood programs that deliver carefully designed in-

terventions with well-defined objectives and that include well-designed

evaluations have been shown to influence the developmental trajectories of

children whose life course is threatened by socioeconomic disadvantage,

family disruption, and diagnosed disabilities. Programs that combine child-

focused educational activities with explicit attention to parent-child inter-

action patterns and relationship building appear to have the greatest im-

pacts. In contrast, services that are based on generic family support, often

without a clear delineation of intervention strategies matched directly to

measurable objectives, and that are funded by more modest budgets, ap-

pear to be less effective.

• The elements of early intervention programs that enhance social and

emotional development are just as important as the components that en-

hance linguistic and cognitive competence. Some of the strongest long-term

impacts of successful interventions have been documented in the domains

of social adjustment, such as reductions in criminal behavior.

• The reconciliation of traditional program formats and strategies—

many of which emphasize the importance of active parent involvement and

the delivery of services in the home setting—with the economic and social

realities of contemporary family life is a pressing concern. Particularly ur-

gent is the need to ensure access to these intervention programs for parents

who are employed full-time, those who work nonstandard hours, and those

who are making the transition from public assistance to work.

• Early childhood policies and practices are highly fragmented, with

complex and confusing points of entry that are particularly problematic for

underserved segments of the population and those with special needs. This

lack of an integrative early childhood infrastructure makes it difficult to

advance prevention-oriented initiatives for all children and to coordinate

services for those with complex problems.

• The growing racial, ethnic, linguistic, and cultural diversity of the

early childhood population requires that all early childhood programs and

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12 FROM NEURONS TO NEIGHBORHOODS

medical services periodically reassess their appropriateness and effective-

ness for the wide variety of families they are mandated to serve. Poor “take-

up” and high rates of program attrition that are common to many early

intervention programs, while not at all restricted to specific racial, ethnic,

or linguistic groups, nonetheless raise serious questions about whether those

who design, implement, and staff early childhood programs fully under-

stand the meaning of “cultural competence” in

the delivery of health and

human services.

• The general political environment in which research questions are

formulated and investigations are conducted has resulted in a highly prob-

lematic context for early childhood policy and practice. In many circum-

stances, the evaluation of intervention impacts is largely a high-stakes activ-

ity to determine whether policies and programs should receive continued

funding, rather than a more constructive process of continuous knowledge

generation and quality improvement.

•As the rapidly evolving science of early child development contin-

ues to grow, its complexity will increase and the distance between the

working knowledge of service providers and the cutting edge of the science

will be staggering. The professional challenges that this raises for the early

childhood field are formidable.

Recommendations

• Recommendation 9 — Agencies and foundations that support evalu-

ation research in early childhood should follow the example set by the

nation’s successful approach to clinical investigation in the biomedical sci-

ences. In this spirit, the goals of program-based research and the evaluation

of services should be to document and ensure full implementation of effec-

tive interventions, and to use evidence of ineffectiveness to stimulate further

experimentation and study.

• Recommendation 10 — The time is long overdue for state and local

decision makers to take bold actions to design and implement coordinated,

functionally effective infrastructures to reduce the long-standing fragmen-

tation of early childhood policies and programs. To this end, the committee

urges two compelling first steps. First, require that all children who are

referred to a protective services agency for evaluation of suspected abuse or

neglect be automatically referred for a developmental-behavioral screening

under Part C of the Individuals With Disabilities Education Act. Second,

establish explicit and effective linkages among agencies that currently are

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EXECUTIVE SUMMARY 13

charged with implementing the work requirements of welfare reform and

those that oversee the provision of both early intervention programs and

child and adult mental health services.

• Recommendation 11 — A comprehensive analysis of the profes-

sional development challenges facing the early childhood field should be

conducted as a collaborative effort involving professional organizations

and representatives from the wide array of training institutions that prepare

people to work with young children and their families. The responsibility

for convening such a broad-based working group or commission should be

shared among the fields of education, health, and human services.

RESEARCH AND EVALUATION

Research has historically played a significant role in enhancing human

development and preventing, ameliorating, and treating a range of condi-

tions that can begin prenatally, at birth, or during the early years of life. To

identify priorities among the many possible recommendations that could be

made for promising further research, the committee was guided by three

goals.

First, it is clear that the capacity to increase the odds of favorable birth

outcomes and positive adaptation in the early childhood years would be

strengthened considerably by supporting creative collaborations among

child development researchers, neuroscientists, and molecular geneticists.

Second, there is a pressing need to integrate basic research aimed at under-

standing developmental processes with intervention research that assesses

efforts to influence developmental outcomes. Such collaborative initiatives

hold the promise of advancing both understanding of environmental effects

on development and improving the effectiveness of the nation’s early inter-

vention strategies. Third, the entire early childhood evaluation enterprise

warrants a thorough reassessment in order to maximize opportunities for

valid causal inference and generalization, to assess what has been learned

cumulatively across the full array of evaluation studies, and to establish a

constructive environment for discussion of ongoing research and its appli-

cation to policy. The themes and issues presented below are elaborated in

the committee’s full complement of research priorities in the final report.

Integrating Child Development Research,

Neuroscience, and Molecular Genetics

Enormous potential exists at the intersection of child development

research, neuroscience, and molecular and behavioral genetics to unlock

some of the enduring mysteries about how biogenetic and environmental

factors interact to influence developmental pathways. These include: (a)

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14 FROM NEURONS TO NEIGHBORHOODS

understanding how experience is incorporated into the developing nervous

system and how the boundaries are determined that differentiate depriva-

tion from sufficiency and sufficiency from enrichment; (b) understanding

how biological processes, including neurochemical and neuroendocrine

factors, interact with environmental influences to affect the development

of complex behaviors, including self-regulatory capacities, prosocial or

antisocial tendencies, planning and sustained attention, and adaptive re-

sponses to stress; (c) describing the dynamics of gene-environment interac-

tions that underlie the development of behavior and contribute to differen-

tial susceptibility to risk and capacity for resilience; and (d) elucidating the

mechanisms that underlie nonoptimal birth outcomes and developmental

disabilities.

Integrating the Basic Science of Human Development and

the Applied Science of Early Childhood Intervention

There are currently few avenues for integrating knowledge gained from

basic developmental science and from evaluations of early interventions.

Yet both enterprises ultimately seek to improve children’s early outcomes

and life opportunities. A great deal stands to be gained from deliberate

efforts to forge ongoing interactions among scientists engaged in these

complementary yet largely disconnected research traditions. Among the

important objectives to be addressed are: (a) enhanced understanding, de-

tection, and treatment of early precursors of psychopathology; (b) improved

preventive and ameliorative interventions for women and children who are

exposed to biological insults and adverse environmental conditions, as well

as for children with identified disabilities; (c) the identification of modifi-

able mechanisms that link impoverished family resources to both adverse

outcomes for individual children and persistent disparities across groups of

children in learning skills and other developmental capacities; and (d) re-

fined understanding of how interventions and the staff that implement

them can work effectively with families that differ along dimensions de-

fined by race and ethnicity, immigration status, religion, or other cultural

characteristics. The capacity of research to address these objectives will

hinge in part on investments in improving the available tools for measuring

important, but generally neglected early developmental outcomes, such as

the multiple components of self-regulatory and executive capacities, and

the ability to make friends and engage with others as a contributing mem-

ber of a group, as well as on increased efforts to evaluate the biological

systems that are affected by early interventions.

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EXECUTIVE SUMMARY 15

Improving Evaluations of Early Childhood Interventions

To improve the nation’s capacity to learn

,From Neurons to Neighborhoods: The Science of Early Childhood DevelopmentCopyright National Academy of Sciences. All rights reserved.COMMUNICATING AND LEARNING 127To study the process of language learning, the most common techniqueis to do nothing more than observe children as they talk. Early studiesconsisted of diaries that researcher parents made of their own child’s firstutterances. The goal was to write down all of the new utterances that thechild produced. Diary studies were later replaced by audio and videosamples of talk from a number of children, usually over a period of years.The most famous of these studies is Roger Brown’s longitudinal observa-tions of Adam, Eve, and Sarah (Brown, 1973). Because transcribing andanalyzing child talk is so labor-intensive, language acquisition studies typi-cally focus on a small number of children, often interacting with theirprimary caregiver at home. Naturalistic observations of children’s talk canbe supplemented with experimental probes that are used with larger num-bers of children. For example, Berko (1958) gave children nonsense wordsand asked them to generate novel forms in different contexts (e.g., “This isa wug. Now there are two of them. There are two ____?” The child whounderstands English plurals should supply the word “wugs”). Unlike manyareas of developmental research, language acquisition studies have beenconducted across the globe, although typically the studies focus on a smallnumber of children in each culture (see Slobin, 1985).Language Learning is a Resilient ProcessLanguage learning turns out to be remarkably similar across cultures.Children exposed to markedly different languages follow similar develop-mental trajectories as they learn their native language. Six-month-old in-fants can distinguish the full range of sounds used in the world’s languages,but by age 1 they have lost many of these distinctions as they focus in ontheir own culture’s language. Children the world over produce their firstwords between 10 and 15 months (“mine,” “shoe”); they then learn thatthe word can be composed of smaller, meaningful parts (morphology,e.g.,“shoe” + “s”) and that the word is a building block for larger, mean-ingful phrases and sentences (syntax, e.g., “my shoe”). Most 18-month-olds have begun a word-learning explosion, acquiring (on average) 9 newwords a day, every day, throughout the preschool years (Carey, 1978).They also begin to produce two-word strings that are highly similar acrosslanguages in two respects. First, the content is the same. Children note theappearance and disappearance of objects, their properties, locations, andowners and comment on the actions done to and by objects and people.Second, the words in these short sentences are consistently ordered in waysthat mirror adult word orders (e.g., “drink juice,” “Mommy give”).By the time children are 3 years old, full sentences are the norm (“I wishI could sit on a horse and ride him to every house in the world”; Hoff-Ginsberg, 1997). These sentences often involve elaborating one element ofhttp://nap.nationalacademies.org/9824From Neurons to Neighborhoods: The Science of Early Childhood DevelopmentCopyright National Academy of Sciences. All rights reserved.128 FROM NEURONS TO NEIGHBORHOODSa single proposition (“baby drinking big bottle”) or combining two propo-sitions with a conjunction (“maybe you can carry that and I can carrythis”). Three-year-olds can also show some remarkably subtle capabilitiesfor language comprehension. For example, consider a child who is told thata little girl fell and ripped her dress in the afternoon and reported the eventto her mother later that night. When 3-year-olds are asked, “When did thegirl say she ripped her dress?” they will provide one of two possible answers(in the afternoon, or at night), but when asked “When did the girl say howshe ripped her dress?” they will provide only one (at night). By age 4 or 5,children all over the world have mastered the fundamental (and many ofthe fine points) of the grammatical system of their native language, includ-ing verb declensions, gender agreement, embedded clauses, and the like(Brown, 1973; Slobin, 1985).This common trajectory of language acquisition is particularly strikinggiven the variability in input that children receive across cultures. In allcultures, language is one of the most powerful symbolic systems throughwhich children learn to understand and interpret human behavior(Harwood et al., 1995). How language is used in the context of socialinteraction is just as important as what is said. For example, in somecultures, children are commonly spoken to directly as participants in con-versation; in other cultures, children primarily overhear talk that is directedtoward others. Despite large differences of this sort, children proceed quiteuniformly with the task of language learning (Ochs and Schieffelin, 1984).Another example is cross-cultural research on narrative constructions,which reveals both considerable overlap across cultures in the narrativesthat caregivers use with their children and also striking differences thathave an impact on the child. For example, Taiwanese mothers tend to tellnarratives that make explicit reference to moral rules and point out thechild’s wrongdoing. European-American mothers, by contrast, emphasizethe entertainment function over the didactic function and go to great lengthsto portray the child in a positive light (Miller et al., 1996). Children whohear stories of this sort not only learn how to build their own culturallyappropriate narratives, but they also learn the social value of their behav-iors, as noted in Chapter 7.Language learning proceeds apace even when the child is faced withlearning two languages simultaneously (de Houwer, 1995; Hakuta, 1986;National Research Council and Institute of Medicine, 1997). Children be-coming bilingual from birth are not dramatically slowed in their develop-ment and appear to develop each language as they would had it been theironly tongue. The problematic issue in the case of bi- or multilingualism isless one of language acquisition than of language retention, which can bemade difficult when one language is not used or valued by nonfamily adultsor institutions, such as the schools, peer groups, and the broader societyhttp://nap.nationalacademies.org/9824From Neurons to Neighborhoods: The Science of Early Childhood DevelopmentCopyright National Academy of Sciences. All rights reserved.COMMUNICATING AND LEARNING 129(National Research Council and Institute of Medicine, 1997, 1998b). Forexample, language loss (of Spanish) among Mexican-American childrenincreases rapidly across first-, second-, and third-generation children(Hakuta and D’Andrea, 1992). Finally, although language development ismarkedly delayed among children raised in low-stimulating orphanages(Rutter, 1981a), once placed in supportive families, children develop lan-guage even with the added challenge, in most of the cases that have beenstudied, of learning a new language.Thus, language learning is apparently a very robust process. Wheredoes this robustness come from? One way to address this question is tosystematically vary either the learner or the learning environment, observ-ing the effects of these variations on subsequent language development. Asan example from another species, Marler raised two closely related butgenetically distinct varieties of sparrows from the egg in identical environ-ments, exposing them to a common collection of songs typical for both(Marler, 1990). He found that the two varieties learned different songs outof the same collection, each variety apparently zeroing in on different as-pects of the input. The range of possible outcomes in the learning process,for this species and for this skill, appears to have been narrowed by theorganism itself.For obvious ethical reasons, researchers cannot deliberately

From neurons to neighborhoods - Inglês (2024)