Published online by Cambridge University Press: 15 October 2009
Genotype–environment interaction, the topic of the preceding chapter, denotes an interaction in the statistical, analysis-of-variance sense of a conditional relationship: The effect of environmental factors depends on genotype. In contrast, genotype–environment correlation literally refers to a correlation between genetic deviations and environmental deviations as they affect a particular trait. In terms of a 2 × 2 table depicting low versus high genotypes reared in low versus high environments, evidence for genotype–environment interaction is obtained from a comparison of cell means (e.g., cells 1 and 4 vs. cells 2 and 3). In contrast, genotype–environment correlation is indicated by the frequency of individuals in the cells (e.g., more children of “high genotype” are likely to experience the “high environment”). In other words, genotype–environment correlation describes the extent to which children are exposed to environments on the basis of their genetic propensities. For example, if shyness is heritable, children genetically predisposed toward shyness will have shy parents on the average who are likely to provide a “shy” environment for their children – that is, modeling shy behavior and providing relatively few opportunities for interactions with strangers. Such proclivities can be reinforced in interactions with nonfamily members: Reactions of unfamiliar children and adults to a shy child are unlikely to be rewarding or successful for the child, thus enhancing the child's tendencies toward shyness.