Thirty Years of Research on Race Differences in Cognitive Ability

Thirty Years of Research on Race Differences in Cognitive Ability is an article by J. Philippe Rushton and Arthur Jensen which forms the centerpiece of the June 2005 edition of Psychology, Public Policy and Law, dedicated to "the thorny issue of race differences in cognitive ability." The issue included commentary from five other researchers and a response from the authors. Rushton and Jensen survey the literature concerning racial differences in intelligence, concluding that genetic factors explain 50% to 80% of the black-white-Asian difference in cognitive ability. The article has been widely criticized as, at least, speculative and political if not racist and eugenicist.
Rushton and Jensen identify 10 categories of research which, in their view, support the hypothesis that racial differences in measured intelligence are partially genetic.

# the world-wide evidence of a consistent black-white-Asian difference
# the greater black-white difference on g-loaded subtests than on culture-bound subtests
# the greater black-white difference on highly heritable subtests than on culturally malleable subtests
# the association of the black-white-Asian difference with differences in brain size
# the persistence of the black-white-Asian difference among trans-racial adoptees
# the consistency of the black-white difference with studies of racial admixture
# regression of black and white relatives (offspring or siblings) to their respective racial means
# consistency of the black-white-Asian IQ differences with differences in 60 other behavioral traits
# consistency of the black-white-Asian differences with evolutionary explanations
# the inability to explain black-white-Asian differences with a zero-genetic model or even with a 50-percent environmental model.

Richard Nisbett, in Appendix B to his book Intelligence and How to Get It, provides a summary and critique of these arguments. Nisbett writes

In sum, the indirect arguments for genetic determinants of the black/white gam in IQ are inherently weak and readily refuted. The most direct evidence—the only evidence that really counts—concerns the European heritage within the black population. With a single exception—which happens to be the only study reported on at any length by either Hernstein and Murray (1994) or Rushton and Jensen (2005)—the data show that more European genes are not advantageous for blacks. The last thirty years have seen a reduction in the gap in IQ by about a third and a reduction in the academic achievement gap by anout the same amount. The evidence favors a completely environmental explanation of the remaining difference between blacks and whites.

After providing a point-counterpoint reply to Nisbett, Rushton and Jensen argue that a "preponderance of evidence" supports their position.

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