Behavioral genetic methods are designed to estimate the relative influence of genetic and environmental factors on individual differences in a trait or in symptoms of a disorder. The influence of genes is quantified by estimating her-itability, the proportion of the population variance in a trait that is attributable to genetic influences. The proportion of variance due to environmental factors can be subdivided into shared and nonshared environmental influences. Shared environmental influences are those that similarly influence members of a family, thereby increasing the similarity of individuals within a family in comparison to unrelated individuals in the population. In contrast, nonshared environmental influences either affect just one individual in a family or have a different effect on different family members. In either case, nonshared environmental influences are those that lead to differences among individuals in a family.
Was this article helpful?