Behavioral Genetics

Behavioral genetics is scientific research that uses genetic methods to investigate the nature and origins of individual differences in behavior. While the field emphasizes genetic influences, it broadly investigates the extent of both genetic and environmental factors in individual differences, and it develops research designs that remove the confound between genes and environment. Founded by Francis Galton in the late nineteenth century, the field was discredited through its association with eugenics before and during the Second World War, before regaining prominence in the late twentieth century through twin and family studies of human behavior and mental illness inheritance and through selective-breeding research on model organisms, and it was transformed again by molecular genetics technology that allows direct measurement and modification of the genome, including knockout mice and human genome-wide association studies. The field's broad findings are that nearly every researched behavior shows a significant genetic influence that increases into adulthood, that most human behaviors are influenced by very large numbers of genes each with a small individual effect, and that environmental influences strongly affect behavior in ways that tend to make family members more different from each other rather than more alike.