Cognitive change in aging: identifying gene-environment correlation and nonshared environment mechanisms.

We describe gene-environment processes that may help account for individual differences in successful aging. Our emphasis is on successful aging in the cognitive domain, wherein individuals come to use a variety of strategies to cope with changes in cognitive capacities. We focus on the role of executive control in particular and define gene-environment correlation and nonshared environmental mechanisms. The quantitative genetic methods used to identify these mechanisms are described, with examples from research in childhood, where such studies are now common. Future work will be most effective if it is guided by life-span development frameworks that address these processes, such as the developmental genotype-->environment theory of Scarr and McCartney and the selection/optimization/compensation theory of Baltes and Baltes.