Abstract
Blacks generally score significantly lower on intelligence tests than Whites. Spearman’s hypothesis predicts that there will be large Black/White differences on subtests of high cognitive complexity, and smaller Black/White differences on subtests of lower cognitive complexity. Spearman’s hypothesis tested on samples of Blacks and Whites has consistently been confirmed in many studies on children and adolescents, but there are many fewer studies on adults. We carried out a meta-analysis where we collected the existing tests of Spearman’s hypothesis on adults and collected additional datasets on Black and White adults that could be used to test Spearman’s hypothesis. Our meta-analytical search resulted in a total of 10 studies with a total of 15 datapoints, with participants numbering 251,085 Whites and 22,326 Blacks in total. For all these data points, the correlation between the loadings of a general factor that is manifested in individual differences on all mental tests, regardless of content (g) and standardized group differences was computed. The analysis of all 15 data points yields a mean vector correlation of 0.57. Spearman’s hypothesis is confirmed comparing Black and White adults. The differences between Black and White adults are strongly in line with those previously found for children and adults; however, because of lack of access to the original data, we could not test for measurement invariance.
Highlights
IQ test scores are well-known as excellent predictors of many economic, educational, and social criteria [1], and group differences in mean intelligence are of great interest
The meta-analytical sample-size weighted correlation of rho = 0.57 we found for adults is highly similar to the mean correlation found in Jensen [1], who reported a correlation of r = 0.59
The differences between Black and White adults are very strongly in line with those previously found for children and adults
Summary
IQ test scores are well-known as excellent predictors of many economic, educational, and social criteria [1], and group differences in mean intelligence are of great interest. By far the most extensively researched is that between the two largest populations in the United States: Whites, or Caucasians, and Blacks, or African Americans [1]. The American Black population scores below the White population by about 1.2 standard deviations (SDs), or 18 IQ points. Te Nijenhuis, Al-Shahomee, van den Hoek, Allik, Grigoriev, and Dragt [3] describe how a well-established empirical finding—the manifold of positive correlations among measures of various mental abilities—is generally considered to be evidence of a general factor in all of the measured abilities. The use of the method of factor analysis makes it possible to determine the degree to which each of the variables is correlated with the factor that is common to all the variables in the analysis
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