DIFFERENCES IN COGNITIVE ABILITY
J. Philippe Rushton
The University of Western Ontario
Arthur R. Jensen
University of California, Berkeley
The culture-only (0% genetic–100% environmental) and the hereditarian (50% genetic–50% environmental) models of the causes of mean Black–White differences in cognitive ability are compared and contrasted across 10 categories of evidence: the worldwide distribution of test scores, g factor of mental ability, heritability, brain size and cognitive ability, transracial adoption, racial admixture, regression, related life-history traits, human origins research, and hypothesized environmental variables. The new evidence reviewed here points to some genetic component in Black–White differences in mean IQ. The implication for public policy is that the discrimination model (i.e., Black–White differences in socially valued outcomes will be equal barring discrimination) must be tempered by a distributional model (i.e., Black–White outcomes reflect underlying group characteristics). Section 1: Background
Throughout the history of psychology, no question has been so persistent or so resistant to resolution as that of the relative roles of nature and nurture in causing individual and group differences in cognitive ability (Degler, 1991; Loehlin, Lindzey, & Spuhler, 1975). The scientific debate goes back to the mid-19th century (e.g., Galton, 1869; Nott & Glidden, 1854). Starting with the widespread use of standardized mental tests in World War I, average ethnic and racial group differences were found. Especially vexing has been the cause(s) of the 15-point Black–White IQ difference in the United States. In 1969, the Harvard Educational Review published Arthur Jensen’s lengthy article, “How Much Can We Boost IQ and School Achievement?” Jensen concluded that (a) IQ tests measure socially relevant general ability; (b) individual differences in IQ have a high heritability, at least for the White populations of the United States and Europe; (c) compensatory educational programs have proved generally ineffective in raising the IQs or school achievement of individuals or groups; (d) because social mobility is linked to ability, social class differences in IQ probably have an appreciable genetic component; and tentatively, but most controversially, (e) the mean Black–White group difference in IQ probably has some genetic component.
Jensen’s (1969) article was covered in Time, Newsweek, Life, U.S. News & World Report, and New York Times Magazine. His conclusions, the theoretical issues they raised, and the public policy recommendations that many saw as stemming directly from them were dubbed “Jensenism,” a term which entered the J. Philippe Rushton, Department of Psychology, The University of Western Ontario, London, Ontario, Canada; Arthur R. Jensen, School of Education, University of California, Berkeley. Correspondence concerning this article should be addressed to J. Philippe Rushton, Department of Psychology, The University of Western Ontario, London, Ontario N6A 5C2, Canada. E-mail: email@example.com
Psychology, Public Policy, and Law
2005, Vol. 11, No. 2, 235–294
Copyright 2005 by the American Psychological Association
1076-8971/05/$12.00 DOI: 10.1037/1076-8918.104.22.168
dictionary. Since 1969, Jensen has continued to publish prolifically on all of these issues, and increasing numbers of psychometricians and behavioral geneticists have come to agree with one or more of the tenets of Jensenism (Snyderman & Rothman, 1987, 1988).
The Bell Curve (Herrnstein & Murray, 1994) presented general readers an update of the evidence for the hereditarian position along with several policy recommendations and an original analysis of 11,878 youths (including 3,022 Blacks) from the 12-year National Longitudinal Survey of Youth. It found that most 17-year-olds with high scores on the Armed Forces Qualification Test, regardless of ethnic background, went on to occupational...