From Neurons to Neighborhoods The Science of Early Childhood Development (2000) / Chapter Skim
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Pages 40-57
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From page 40... ...
. Yet an emphasis on whether hereditary constraints or environmental incentives are the preeminent influence in human development 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 intervention programs, family support, delinquency and criminality, and other issues of child and family policy.
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From page 41... ...
Moreover, by contrast with a traditional view that heredity imposes limitations 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 genetics, and brain development.
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From page 42... ...
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 structural equations modeling and other quantitative model-fitting methods for estimating genetic and environmental contributions to behavioral variability.
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From page 43... ...
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 development of antisocial behavior in children was influenced by heritable characteristics which altered the childrearing climate of the home and by family influences that arose independently of the child.
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From page 44... ...
There are comparable statistics that estimate environmental contributions to individual characteristics. Unfortunately, the distillation 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.
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From page 45... ...
Environmental 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 nutrition and medical care, even though individual differences in height are strongly influenced by heredity.
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From page 46... ...
Environmental interventions which can include improved education, health care, nutrition, and caregiving can significantly improve developmental outcomes for children, even though individual differences in those outcomes may be strongly influenced by genetic processes. Heritability does not imply constraints on change.
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From page 47... ...
Shared and Nonshared Environmental Effects Research in developmental behavioral genetics has also elucidated features of environmental influence on individual differences. In particular, researchers have helpfully distinguished between shared and nonshared environmental influences.
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From page 48... ...
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 observational and experimental studies, strong conclusions from developmental behavioral genetics research about how parents influence their children in shared or nonshared ways must remain tentative.
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From page 50... ...
MOLECULAR GENETICS Developmental behavioral genetics examines nature and nurture inclirectly through the behavioral characteristics of genetically related and unrelateci inclivicluals. But it would be far more informative if researchers could identify specific, incliviclual genes associated with distinctive human characteristics, examining their behavioral consequences in concert with particular environmental influences.
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From page 51... ...
In one investigation, for example, rhesus monkeys with a specific genetic vulnerability affecting neuroendocrine functioning who grew up under adverse (peer-rearing) conditions consumed more alcohol in experimental conditions (Campbell et al., 1986a)
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From page 52... ...
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 interaction is important not only to understanding developmental psychopathology 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.
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From page 53... ...
, and thus brain development 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 unequalled by any other (fruit flies don't have books, movies, radio, or televi ~ .
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From page 54... ...
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)
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From page 55... ...
More importantly, their coaction provides the impetus for development, whether it is viewed from the perspective of "experience-expectant" brain growth or the interplay between of genes and environments. The developmental action is in the interaction of nature and nurture.
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From page 56... ...
1 here is, in other words, a very broad range of individual differences in which the boundaries between the normative and the atypical are matters of degree rather than quality. This means that, in studying the growth of typical children, researchers gain insight into the developmental dynamics of atypicality and that, conversely, efforts to understand the challenges of children with developmental disorders yield insights into normative growth.
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From page 57... ...
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)
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