Do age-group differences on mental tests imitate racial differences?

Previous studies have shown that the pattern of mean differences on various mental tests (and other psychometric features) between black (B) and white (W) children all of the same age is imitated by comparing racially homogeneous groups composed of all W or all B children that differ in chronological age (CA). When the younger/older CA ratio is between 0.80 and 0.90, raw score differences approximate the B-W mental age (MA) ratio of same-age B and W children on IQ tests. The typical W-B IQ difference is 10-20 points. The imitation of actual same-age W-B mean differences by different age groups of W (or B) has been observed in a number of psychometric characteristics besides total raw scores. Does the same "imitation" phenomenon occur for Spearman's hypothesis? This hypothesis states that the standardized mean W-B differences on various tests are directly related to the magnitudes of the tests' g loadings? In a battery of 17 diverse tests, the actual W-B comparisons strongly bear out Spearman's hypothesis. The comparisons of different age groups (of the same race) resemble the Spearman effect, but also clearly differ, as the least g-loaded tests show larger age-group differences than the corresponding differences between the age-matched W and B groups. The findings support Spearman's hypothesis that the W-B difference in test performance is predominantly a g difference rather than a unitary developmental difference affecting all factors in test performance. (C) 2003 Elsevier Science Inc. All rights reserved.