Spearman’s g Explains Black-White but not Sex Differences in Cognitive Abilities in the Project Talent
OpenPsych , July 18, 2025, ISSN: 2597-324X
The weak form of Spearman’s Hypothesis, which states that the racial group differences are primarily due to differences in the general factor (g), was tested and confirmed in this analysis of the Project Talent data, based on 34 aptitude tests among 9th-12th grade students. Multi-Group Confirmatory Factor Analysis (MGCFA) detected small-modest bias with respect to race but strong bias with respect to within-race sex cognitive difference. After establishing partial measurement equivalence, SH was tested by comparing the model fit of correlated factors (non-g) model with a bifactor (g) model as well as the relative contribution of g factor means to that of the specific factors. While g was the main source of the Black-White differences, this wasn’t the case for within-race sex differences. The average proportion of the score gaps accounted for by g is large (.73/.90) for the Black-White analysis but modest (.43/.50) for the sex analysis. The evidence of measurement bias in the sex analysis may cause ambiguity in interpreting SH for sex differences. Results from MGCFA were somewhat corroborated by the Method of Correlated Vectors, with high correlations of subtests’ loadings with Black-White differences but near-zero correlations with sex differences. This finding replicates earlier MGCFA studies supporting SH with respect to the Black-White cognitive gap as well as earlier MGCFA studies revealing stronger gender bias than racial bias.
