ABSTRACT
The field of quantitative behavioral genetics draws inferences about genetic and environmental influences on behavior using genetically informed designs. Most of these designs employ comparisons between monozygotic (MZ) twins and dizygotic (DZ) twins or, in adoption studies, compare characteristics of birth parents with comparable characteristics of their adopted children. Nowadays, this field is often conceived as a preliminary and indirect peek at the influences of specific genes on behavior. According to this view, we are now on the threshold of a new era in which advances in molecular genetics will provide a much clearer and more precise view of how specific genes shape our thoughts and actions. The recent preliminary maps of the human genome have heightened interest in this prospect. The simple optimism inherent in these hopes obscures a very different role for quantitative genetics. In fact, these familiar tools now promise developments that are more realistic and closer at hand, serving to unravel the relationship between family dynamics and child development. First, they can help us properly weigh the role of children themselves in evoking and influencing the dynamics of their own families. Second, these tools can help clarify reciprocal child and parent influences as they unfold across development. Third, they can help delineate those aspects of families that make them more or less vulnerable to these influences. These new uses of familiar tools may lead us to surprising places. They may improve understanding of the interplay between genetic and social influences in development and provide an even fuller understanding of how genetic influences are expressed in thought and behavior. I will review some of the logic of quantitative behavioral genetics and illustrate its relevance for understanding child effects and reciprocal responses from families.
