New Evidence Race IQ Gap Remains—Could Undermine Affirmative Action Policies

Nov. 9, 2006 – A study published in the October 2006 issue of Psychological Science showed the same Black-White IQ difference in large standardization samples for four major IQ tests.

The researchers reported on the Wonderlic Personnel Test, the Kaufmann Assessment Battery for Children, the Woodcock-Johnson test, and the Differential Ability Scale, which all combined to show a Black gain of less than 1 IQ point over the last 30 years.

The study’s authors were veteran IQ researchers J. Philippe Rushton of the University of Western Ontario and Arthur R. Jensen of the University of California at Berkeley.

Rushton and Jensen’s article countered claims made in the same journal by William Dickens of the Brookings Institute and James Flynn of the University of Otago in New Zealand, who had presented data showing the Black-White IQ differences narrowing by 4 to 7 points.

“Such claims have been routine over several decades,” said Prof. Rushton. “When the totality of the available evidence is examined, the alleged evidence disappears.”

“The Black-White IQ difference in the United States has remained at 15 to 18 points, or 1.1 standard deviations, for nearly a century,” said Rushton. “It was first clearly established in 1917 by an analysis in the U.S. Army of 23,596 Black draftees who had an IQ of 83 (vs. 100 for Whites).”

“Military samples continued to show the same gap during World War II, the Korean War, and the Vietnam War era,” he said.

The Black-White gap was also shown in 2001 in an analysis of 6,246,729 individuals from military, corporate, and higher education samples published by Philip Roth and colleagues in Personnel Psychology.

Rushton and Jensen said their new study confirmed their earlier conclusion that Black-White IQ differences are 80% heritable, an estimate based on a review of the literature in the 2005 Psychology, Public Policy, and Law. Rushton argued that given that the IQ differences were 80% genetic, no more than a 3-IQ point convergence would be possible.

Prof. Rushton said the results explained the under-representation of Blacks in high IQ occupations.

Rushton also said the results could undermine affirmative action policies as the US Supreme Court’s 2003 decision on the University of Michigan only being permitted affirmative-action on the assumption that Black-White test scores were converging. That assumption has been shown to be untrue.

Prof. Rushton said that his study was not the only one showing the non-narrowing of the race differences. He pointed to Charles Murray’s 2005 article in Commentary and the just published article by Murray in the November-December issue of the Intelligence, which showed no narrowing on the Peabody Achievement Tests.

Corresponding author: J. Philippe Rushton, Department of Psychology, University of Western Ontario, London, Ontario, N6A 5C2, Canada. Email: Tel: 519-661-3685.

On the Web: Article pdf:

Complete Reference: Rushton, J. P., & Jensen, A. R. (2006). The totality of available evidence shows race-IQ gap still remains. Psychological Science, 17, 921-922.

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