Human psychosexual development involves three primary components: core gender identity, the sense of self as male or female; sexual orientation, erotic interest in individuals of the same or the other sex; and gender role behaviors, the myriad characteristics that are associated with being male or female or that differ on average for males and females (Green, 1974; Hines, 2004). Determinants of these components are thought to be both biological (genetic and hormonal) and social-cognitive (involving reinforcement and modelling of gender typical behavior; Hines, 2004). This paper focuses on the role of androgens, the primary hormones produced by the testes, in psychosexual development. The hypothesis that androgens influence human psychosexual development is based on evidence that androgens influence sex-related development in other mammals. During critical periods of early life, high levels of androgen promote male-typical neural and behavioral characteristics, whereas low levels produce female-typical characteristics (see De Vries & Simerly, 2002; Goy & McEwen, 1980, for reviews). These hormonal effects have been demonstrated most clearly for reproductive behaviors, such as the mounting of female animals by males and the receptive lordosis posture adopted by females in response to these mounts. For example, female rodents and nonhuman primates who are treated with testosterone or other androgens during early development show increased male-typical behavior (mounting) and decreased female-typical behavior (lordosis) in adulthood. Similarly, male animals denied testosterone during early life show decreased mounting and increased lordosis as adults. Early manipulations of androgens also influence other behaviors that show sex differences. For instance, treating female rats or rhesus monkeys with testosterone during early development increases subsequent rough-and-tumble play, a behavior that normally is more common in males than in females (Goy & McEwen, 1980; Meaney & Stewart, 1981).
