Heredity and Environment

Topics: Intelligence quotient, Black people, Intelligence Pages: 14 (4900 words) Published: October 15, 2012
Psychology, Public Policy, and Law 2005, Vol. 11, No. 2, 302–310

Copyright 2005 by the American Psychological Association 1076-8971/05/$12.00 DOI: 10.1037/1076-8971.11.2.302

HEREDITY, ENVIRONMENT, AND RACE DIFFERENCES IN IQ A Commentary on Rushton and Jensen (2005) Richard E. Nisbett
University of Michigan J. P. Rushton and A. R. Jensen (2005) ignore or misinterpret most of the evidence of greatest relevance to the question of heritability of the Black–White IQ gap. A dispassionate reading of the evidence on the association of IQ with degree of European ancestry for members of Black populations, convergence of Black and White IQ in recent years, alterability of Black IQ by intervention programs, and adoption studies lend no support to a hereditarian interpretation of the Black–White IQ gap. On the contrary, the evidence most relevant to the question indicates that the genetic contribution to the Black–White IQ gap is nil.

Rushton and Jensen’s (2005) article is characterized by failure to cite, in any but the most cursory way, strong evidence against their position. Their lengthy presentation of indirectly relevant evidence which, in light of the direct evidence against the hereditarian view they prefer, has little probative value, and their “scorecard” tallies of evidence on various points cannot be sustained by the evidence.

The Current Difference in Intelligence Between Blacks and Whites One of the most serious misrepresentations in Rushton and Jensen’s (2005) article is their claim that the current difference in IQ between Blacks and Whites is slightly more than 15 points, or 1 standard deviation. The best evidence we have indicates that that value is out of date and that the Black–White IQ gap has lessened considerably in recent decades (Grissmer, 1994; Grissmer, Flanagan, & Williamson, 1998; Grissmer, Williamson, Kirby, & Berends, 1998; Hedges & Nowell, 1998; Nisbett, 1995, 1998). We do not have actual IQ scores available to establish this point but rather various ability tests, most of which are highly correlated with IQ—some as high as .8 to .9. Though IQ scores would be preferable to speak directly to the question of IQ change, such data are unavailable in the form of a national random sample. In contrast, several probability samples of U.S. elementary and high school students are available. These include, over the period 1965–1994, the Equality of Educational Opportunity (EEO) survey, the National Longitudinal Study, the High School and Beyond survey, the National Education Longitudinal Study, and the National Assessment of Educational Progress program (NAEP). Hedges and Nowell (1998) found improvement on almost all tests for African American 12th graders compared with other 12th graders over the period 1965– 1994. The best estimates in terms of the stability the scores provide, and in terms of their correlations with IQ, are in the form of composites, for example,

Correspondence concerning this article should be addressed to Richard E. Nisbett, Department of Psychology, University of Michigan, Ann Arbor, MI 48109. E-Mail:




reading vocabulary mathematics for the EEO survey. The Black–White gap on these composites over the period decreased on average by 0.13 standard deviation per decade, yielding an estimate of a reduction of the gap by around 0.39 standard deviation over the period. The largest study, conducted by the NAEP, indicated that, if trends were to continue, the gap in reading scores would be eliminated in approximately 25 years and the gap in science scores in approximately 75 years. Grissmer, Flanagan, and Williamson (1998) found comparably large gains on the NAEP for Blacks in elementary school, junior high, and high school. Whites gained slightly in both math and reading between 1971 and 1996, but Blacks gained much more, narrowing the gap by 0.2 to 0.6 standard deviations. This would yield estimates of...

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