Sex-related differences in general intelligence g, brain size, and social status

Abstract

The question of a sex difference in intelligence has long divided the experts. IQ researchers sum standardized subtest scores to calculate intelligence in general, and find that males outscore females by about 3.8 points, whereas factor analysts derive the g factor scores from intertest-correlations and find no consistent sex differences in general intelligence. The latter finding is puzzling, as males have larger average brains than females, and brain size correlates .30–.45 with g (and IQ). Males thus “ought” to score a higher g than females. The present study addressed this paradox by testing four hypotheses: (1) Inadequate analyses explain why researchers get inconsistent results, (2) The proper method will identify a male g lead, (3) The larger male brain “explains” the male g lead, (4) The higher male g average and wider distribution transform into an exponentially increased male–female ratio at the high end of the g distribution, and this largely explains male dominance in society. All four hypotheses obtained support and explain in part why relatively few males dominate the upper strata in all known societies. The confirmation of hypothesis 3 suggests that the brain size—intelligence–dominance link may be partly biological.