What are some common methods used to study genetic influences on behavior?

Common methods used to study genetic influences on behavior include twin studies, adoption studies, and gene mapping. Twin studies help to compare the similarities between identical and fraternal twins to estimate the heritability of a trait. Adoption studies look at the similarities between adopted children and their biological and adoptive parents to determine genetic influences. Gene mapping involves identifying specific genes associated with certain behaviors. Choices A, C, and D are incorrect because genetic influences on behavior are not solely studied through twin studies or family history, and while the understanding of genetic influences may vary, there are established methods to study them.