Sex differences in verbal and spatial ability reconsidered in relation to body size, lung volume, and sex hormones

PubMedID: 12929793 Sex differences in verbal and nonverbal abilities were reconsidered in relation to bodily measures and sex hormones in Turkish university students. Perceptual-verbal ability was evaluated using As Test. To assess the nonverbal abilities, the mental rotation test and Cattell's Culture Fair Intelligence Test were used. As expected, the 53 women performed better than men on the As Test; 79 men had a higher mean than the 53 women on the mental rotation task; there was no sex difference on Cattell's IQ Test. Cattell IQs correlated only with tidal volume of lungs. Scores on the As Test did not show significant correlations with body size and lung capacities. Mental rotation was significantly correlated with height, weight, and lung volume. With covariates of height, weight, and vital capacity, sex differences in mental rotation completely disappeared, but the difference on the As Test increased while Cattell IQ remained sex-neutral. With testosterone as covariate, the sex difference on the As test increased but on the mental rotation task disappeared; Cattell IQ was sex-neutral. With covariates of estradiol and progesterone, sex differences on the As test disappeared; mental rotation scores and Cattell IQ were not influenced. Under a combined covariation of height, weight, and testosterone, sex differences in mental rotation reversed, women scoring better than men; after adding estradiol or progesterone instead of testosterone to this model, sex differences on mental rotation completely disappeared, but verbal ability and Cattell IQ were not changed. These results suggest that Cattell's Culture Fair Intelligence Test is unique in resistance to sex differences; perceptual-verbal ability was the most sex-specific mental trait but with dependence on estradiol; mental rotation, on the contrary, was least sex-specific, depending on body size, lung volume, sex hormones, and their combined actions, which explains women's better performance.