Behavior Genetics

Behavioral genetics' roots were planted by Francis Galton in the late nineteenth century, but its early efforts were discredited by its association with the eugenics movement in the early twentieth century. Twin, adoption, and family studies helped reestablish the credibility and importance of behavioral genetic research and have supported three general conclusions: (a) Genetic influences on individual differences in behavior are pervasive, (b) the relevant environmental influences are predominantly of the nonshared rather than the shared variety, and (c) the importance of genetic factors appears to increase with age. With the heritability of behavioral phenotypes well established, the field has moved to trying to identify the specific genetic variants that underlie these heritable effects and exploring how these variants interact with environmental factors. Initial efforts in these areas have, however, been hampered by the typically small sample sizes of the relevant research in psychology. The establishment of large-scale consortia and the use of meta-analytic methods are now beginning to reveal the complex genetic architecture of behavioral phenotypes.