Sex differences in brain volume are related to specific skills, not to general intelligence

It has been proposed that males would show higher mean scores than females in general intelligence (g) because (1) men have, on average, larger brains than women, and (2) brain volume correlates with g. Here we report a failure to support the conclusion derived from these premises. High resolution MRIs were acquired in a sample of one hundred healthy young participants for estimating total, gray, and white matter volumes. Participants also completed an intelligence battery – comprising tests measuring abstract, verbal, and spatial abilities – that allowed the extraction of g scores. Results showed consistent relations between sex differences in brain volumes and non-g spatial and verbal skills but not for g.