The study of behavioral variation among individuals, which is separated into genetic versus environmental components. The most common research methodologies employed are family, twin, and adoption studies. Environmental influences are divided into two classes, shared and non-shared (or unique) environment. The former is the environment shared by siblings reared in the same family, and which includes such variables as socioeconomic status and parent education, while the latter is the environment unique to the individual, and which includes such variables as peer group membership. Supposedly founded by Francis Galton (1822-1911), behavior genetics has come along way since then and its practitioners have devised and developed sophisticated statistical techniques for separating the influences of heredity and shared and non-shared environments on behaviour. Problems confronting behavior genetics include definitions of the behaviors in question (e.g., personality traits such as shyness) and the fact that behavior involves multiple genes, something that complicates the search for genetic contributions. In more recent years, with advances in molecular biology, behavior genetics has become engaged in the search for stretches of DNA or locations on chromosomes that are associated with particular behaviors, and which has been successful for mental disorders such as schizophrenia and bipolar disorder. In a sense, some behavior geneticists are cross-disciplinarians in that they have been trained in both genetics and psychology.
See Co-twin method, Developmental genetics, Environment, Epistatic/epistasis, Hereditary, Heritability, Human Connectome Project (HCP), Interdisciplinarity, Interdiscipline, Molecular biology, Non-shared environment, Polygenic mode of inheritance, Polygenes, Quantitative genetic theory, Shared environment