A study of the dynamics of sex differences in adulthood.

Studies of gender differences using primarily young individuals show that males, on average, perform better than females in physical activities but worse than females on tests of verbal abilities. There is however a controversy about the existence of these sex differences in adulthood. Our study used 1271 participants from four cultural backgrounds (Chinese, multi-generation Canadians, Indu-Canadians, and European-Canadians) divided in five age groups. We measured sex differences in the time required for participants to complete a lexical task experiment, and also assessed their verbal tempo and physical endurance using a validated temperament test (Structure of Temperament Questionnaire). We found a significant female advantage in time on the lexical task and on the temperament scale of social-verbal tempo, and a male advantage on the temperament scale of physical endurance. These sex differences, however, were more pronounced in young age groups (17-24), fading in older groups. This "middle age-middle sex" phenomenon suggests that sex differences in these two types of abilities observed in younger groups might be "a matter of age," and should not be attributed to gender in general. A one-dimensional approach to sex differences (common in meta-analytic studies) therefore overlooks a possible interaction of sex differences with age.