Effects of estrogen changes during the menstrual cycle on spatial performance

Genetic influences on sex differences in outstanding mathematical reasoning ability

Sexual selection provides an adequate partial explanation for the difference in means between the distributions, but fails to explain the difference in variance, that is, the overrepresentation of both boys with outstanding mathematical reasoning ability (OMRA) and boys with mental retardation. Other genetic factors are probably at work. While spatial ability is correlated with OMRA, so are other cognitive abilities. OMRA is not reducible to spatial ability; hence selection for navigational skill is unlikely to be the only mechanism by which males have gained an advantage in OMRA.

Sexual-selection accounts of human characteristics: Just So Stories or scientific hypotheses?

We evaluate three of Geary's claims, finding that (1) there is little evidence for sex differences in object- vs. person-orientation; (2) sex differences in competition, even if biologically caused, lead to sex differences in mathematics only given a certain style of teaching; and (3) sex differences in mental rotation, though real, are not well explained in a sociobiological framework or by the proximate biological variables assumed by Geary.

A critic with a different perspective

To the extent that Geary's theory concerning biologically primary and secondary behaviors depends on factor analytic methods and findings, it is woefully weak. Factors have been mistakenly called primary mental abilities, but the adjective “primary” represents reification of a mathematical dimension defined by correlations. Fleshing out a factor beyond its mathematical properties requires much additional quantitative experimental and correlational research that goes far beyond mere factoring.

Omissions relevant to gender-linked mathematical abilities

Analyses of bodies of data usually omit some relevant studies. Geary omits (1) some studies looking at functional correlates of basic biological data, (2) studies of developmental implications for functioning, and (3) the recent achievement of acceleration of cognitive development.

Resources dimorphism sexual selection and mathematics achievement

Geary's model is a worthy effort, but ambiguous on important issues. It ignores differential resource allocation, although this follows directly from sexual selection via differential parental investment. Dimorphism in primary traits is arbitrarily attributed to sexual selection via intramale competition, rather than direct evolutionary pressures. Dubious predictions are made about the consequences of raising mathematics achievement.

The logic of the sociobiological model Geary-style

Geary's is the traditional view of the sexes. Yet each part of his argument – the move from sex differences in spatial ability and social preferences to a sex difference in mathematical ability, the claim that the former are biologically primary, and the sociobiological explanation of these differences – requires considerable further work. The notion of a biologically secondary ability is itself problematic.

Some problematic links between hunting and geometry

Geary's emphasis on hunting ignores the possible importance of other human activities, such as scavenging and gathering, in the evolution of spatial abilities. In addition, there is little evidence that links spatial abilities and math skills. Furthermore, such links have little practical importance given the small size of most differences and girls' superior performance in mathematics classrooms.

Menstrual cycle, arousal-induction, and intelligence test performance

Regularly menstruating students (aged 19 to 25 yr.) were tested in the morning under high and low arousal-induction conditions (with time-pressure instructions vs without time-pressure instructions) during either midcycle (n = 16 or menstruation phase (n = 16) to study the interactive effects of menstrual phases and time-pressure stress-induced arousal on intelligence test scores on Raven's Standard Progressive Matrices and Hundal's General Mental Ability Test. A crossover interactive effect of menstrual phase and stress-induced arousal was found on performance of the Hundal test, suggesting that performance of subjects who were tested during the midcycle phase (putatively High Basal Arousal) was impaired under the time-pressure instructions condition (High-induced Arousal) as compared to performance under the without time-pressure instructions condition (Low-induced Arousal), with the reverse pattern of effects being true for subjects who were tested during the menstruation phase. Scores on Hundal's test conform to the Yerkes-Dodson (1908) law which relates arousal to task performance and suggests that the menstrual cycle and performance on the intelligence test was arousal-based. No effects, however, were observed for Raven's Matrices, raising the possibility that task characteristics may mediate the relationship between arousal and performance.