There is evidence that biological factors, including genes, are correlated with an individual’s sexual orientation. But as we are often reminded, correlation is not necessarily causation. This entry describes a developmental theory of sexual orientation that proposes that biological factors do not, in fact, directly influence an individual’s sexual orientation but act indirectly by influencing the child’s preferences for sex-typical or sex-atypical activities. Children who prefer sex-typical activities and who play primarily with same-sex playmates are called gender conforming; children who prefer sex-atypical activities and who play primarily with opposite-sex playmates are called gender nonconforming. These preferences lead children to feel different from either opposite- or same-sex peers—to perceive them as dissimilar or exotic. Gender-conforming children will experience opposite-sex children as different from themselves, and ...