As every parent, teacher, and developmental psychologist knows, male and female children become "masculine" and "feminine," respectively, at a very early age. By the time they are four or five, for example, girls and boys have typically come to prefer activities defined by the culture as appropriate for their sex and also to prefer same-sex peers. The acquisition of sex-appropriate preferences, skills, personality attributes, behaviors, and self-concepts is typically referred to within psychology as the process of sex typing. The universality and importance of this process is reflected in the prominence it has received in psychological theories of development, which seek to elucidate how the developing child comes to match the template defined as sex appropriate by his or her culture. Three theories of sex typing have been especially influential: psychoanalytic theory, social learning theory, and cognitive-developmental theory. More recently, a fourth theory of sex typing has been introduced into the psychological literature-gender schema theory. This article is designed to introduce gender schema theory to feminist scholars outside the discipline of psychology. In order to provide a background for the conceptual issues that have given rise to gender schema theory, I will begin with a discussion of the three theories of sex typing that have been dominant within psychology to date.