Negligible sex differences in general intelligence

The general factor, g, can be extracted from a correlation matrix of a battery of mental ability tests. g is common to all mental abilities. A key question in the research on cognitive sex differences is whether, on average, females and males differ in g. This question is technically the most difficult to answer and has been the least investigated. Cognitive batteries were applied in the present study to independent samples totaling 10,475 adult subjects (4,256 females and 6,219 males). The scores were factor-analyzed by sex to obtain separate g factors. The congruence coefficients (r(c)) suggested a near identity of these factors. Then, three methods were used to know if the standardized sex differences (ds) are explained by g: (1) the method of correlated vectors; (2) the sex loading in g was computed including the point-biserial correlation between sex and each of the subtests in the full matrix of subtest intercorrelations for factor analysis; and (3) the correlation between sex and g factor scores. The results suggest a negligible sex difference in g. The present study includes the largest sample on which a sex difference in gr has ever been tested. The findings are consistent with those using quite different test batteries and subject samples.