An alternative approach on which biology leaves its signature is Evolutionary Psychology . Genes Versus Environment Behavior genetics is a field in which variation among individuals is separated into genetic versus environmental components. The most common research methodologies are family studies, twin studies, and adoption studies. Shared environment is the environment shared by siblings reared in the same family. This includes such variables as socioeconomic status and parent education.
Nonshared environment is the environment unique to the individual.
This includes such variables as peer group. It is important to note that there is no single gene for intelligence, personality traits, behavior, or even height. Rather, such complex characteristics are polygenic, i.e., they are influenced by multiple genes. The research methodologies mentioned do not tell us which genes are involved, only the relative influence of all genes as opposed to environment. Methodologies Family Studies Children share 50 percent of their genes with each parent.