Sex differences in reasoning abilities: Surprising evidence that male-female ratios in the tails of the quantitative reasoning distribution have increased

Sex differences in cognitive abilities, particularly at the extremes of ability distributions, have important implications for the participation of men and women in highly valued and technical career fields. Although negligible mean differences have been found in many domains, differences in variability and high ratios of males to females in the tails of the ability distribution have been found in a number of studies and across domains. A few studies have also observed trends over time, with some noting the decreasing ratios of boys to girls in the highest levels of mathematics test performance. In this study, sex differences in means, variances, and ratios were evaluated in four cohorts (1984, 1992, 2000, and 2011) in verbal, quantitative, and nonverbal/figural reasoning domains as measured by the Cognitive Abilities Test. Samples included US students in grades 3-11. Overall, the results were consistent with previous research, showing small mean differences in the three domains, but considerably greater variability for males. The most surprising finding was that, contrary to related research, the ratio of males to females in the upper tail of the quantitative reasoning distribution seemed to increase over time. Explanations for this finding are explored.