The relatively simple question of whether sex differences exist has evolved into the more theoretically interesting question of why sex differences occur. This transition has come about because of the meta-analytic investigations of sex differences in social behavior which established sex difference trends in a variety of social behaviors. Many psychologists have questioned the validity of these meta-analytic generalizations since they violate many of the concepts in our textbooks and violate the popular view that sex differences exist only in the minds of perceivers. This role analysis focuses on gender roles, socially constructed rules about male and female behavior. Role theory is in harmony with the overall sex differences established in meta-analyses, tending to be consistent with the normative expectations that women should be communal and men agentic. To account for variability in findings about sex differences, a theory should suggest moderator variables that specify social settings that limit and accentuate sex differences. Meta-analysis is suited to the detection of such interactions between sex and situational variables when the studies differ in theory-relevant aspects of their social settings. Sex differences in behavior may appear stronger in laboratory than in natural settings. Meta-analytic studies should enable development of more valid generalizations about women and men. (ABL)