Sex differences in cognition: A meta-analysis of variance ratios in the Wechsler Intelligence Scales for Children

A meta-analytic approach was used to explore sex differences in within-sex variation across different versions of the Wechsler Intelligence Scale for Children (WISC). Mean sex differences and variance ratios (VRs) were obtained from 75 studies that included 124 independent samples, 571 effect sizes. The outcomes included full scale IQ, individual subtests, and composite indices based on the Cattell-Horn-Carroll ability model (e.g., visual processing, gV, and crystallized intelligence, gC). Although males were more variable in several domains (e.g., gV, gC), females were more variable for processing speed (gS), and there were no VR differences for still other domains (e.g., short-term verbal memory). The cross-domain differences in VRs were linearly related to the magnitude of mean sex differences, suggesting that the sex with the advantage at the mean is often the more variable sex. A theoretical model that accounts for this pattern is proposed.