A Meta-Analysis of Spearman’s Hypothesis in the United States

A comprehensive meta-analysis of vector-correlation tests of Spearman’s Hypothesis (SH) with respect to US White-Black (W-B) cognitive performance differences is conducted. Thirty-one usable studies yielding 44 independent effect sizes were identified, with a total harmonic N of 1,039,379. A random-effects model, using subtest number to estimate inverse-variance weights, yielded a large-magnitude positive mean vector correlation, r = .745, 95% CI [.699, .792], with a prediction interval of .628 to .862, and modest between-study heterogeneity, I² = 25.61%, 95% CI [0.00%, 50.5%]. Sampling error accounted for 46.3% to 82.7% of between-study variance, depending on estimator, suggesting that some variance in those data is potentially due to moderators rather than sampling error. A three-moderator meta-regression including harmonic N , sample mean age, and study year yielded evidence of negative moderation by sample age. SH therefore appears to be weaker in older samples. No quadratic effect of age was detected. Funnel-plot diagnostics using Fisher- z -transformed effects indicated significant unadjusted Egger’s asymmetry, but this became non-significant after adjustment for the moderators. Trim-and-fill imputed no missing effect sizes. The presence of age-dependent moderation, including both reversals and attenuation of effect sizes in older samples, makes claimed isomorphism between g and W-B differences difficult to sustain. The results instead suggest complex environmental confounding potentiating, attenuating, or even reversing the g -dependence of W-B differences.