Individual differences and the canalization of human behavior.

Abstract

Gottlieb (1991) suggests that behavior geneticists and developmental psychologists have underestimated the importance of environmental regulation of species-typical behavior, outlines a theory of how environments and genes interact dynamically as behavior develops, and provides supporting examples from his own and others' laboratories. Although oversimplified explanations of development have occasionally gained currency, we contend that the complexities of genotype-environment relations have been addressed in psychology, with still greater difficulties arising from psychologists 1 interest in individual differences in behavior. The complexities of studying genetic and environmental determination of the development of individual differences are explored, using intelligence as an example. Finally, we outline a research program in the spirit of Gottlieb's contribution.

Gene-by-Socioeconomic Status Interaction on School Readiness

“…The gene × environment interaction observed on early mathematics skill is consistent with proposals (Bronfenbrenner & Ceci, 1994; Turkheimer & Gottesman, 1991) that the expression of genes for cognitive development is dependent on the quality of the larger environmental context in which children are situated. Why was there no gene x environment interaction apparent on reading skill?…”

Genotype by Environment Interaction in Adolescents’ Cognitive Aptitude

“…The socioeconomic advantage of the NMSQT adolescents may be due to two selection processes: (a) for this cohort, only adolescents with a certain level of academic achievement took the NMSQT; (b) of twins identified as potential participants, non-response may have been associated with environmental disadvantage. The modification of heritability within the NMSQT sample suggests that genotype-environment interactions in cognitive ability are not limited to severely disadvantaged environments, as has been previously suggested (Turkheimer and Gottesman 1991;Scarr 1992). …”

“…Rather, the bioecological model is predicting an increase in genetic variance even over the range of normal environments, a slightly different conception of what it means for environmental differences to be "relevant" for children 's functioning. Indeed, Bronfenbrenner and Ceci (1994) predict the identical pattern as Turkheimer and Gottesman (1991): high heritability estimates and low shared environmentality estimates as environmental advantage increases.…”

Family environment and the malleability of cognitive ability: A Swedish national home-reared and adopted-away cosibling control study

“…We prefer a perspective that uses a genetically informative design to estimate the magnitude of environmentally mediated IQ gains as a function of the nature of the environmental change, including the level of the original deprivation and the magnitude of the eventual enhancement. This point of view has been represented in terms of a construct called a reaction norm, in which the development of a phenotype is viewed as the results of the joint effect of genetic and environmental differences, with neither being granted causal priority (17). Despite being demonstrably related to genetic endowment, cognitive ability is environmentally malleable, and the malleability shows plausible doseresponse relations with the magnitude of the environmental differences.…”