Low test scores are routinely observed in sub-Saharan African populations. In this paper, we explore the topic further by examining Rushton and Skuy's [Intelligence 28 (2000) 251] hypothesis that a bimodal distribution exists in the African population with a high-scoring group virtually indistinguishable from Whites, and a low-scoring group performing significantly below both Whites and the higher-scoring African group. To test this hypothesis, we sought out a potentially higher-scoring African population than has previously been studied. We administered untimed Raven's Standard Progressive Matrices (SPM) to 342 17- to 23-year-olds in the Faculties of Engineering and the Built Environment at the University of the Witwatersrand in Johannesburg (198 Africans, 86 Whites, 58 Indians; 71 women, 271 men). Out of the 60 total problems, the African students solved an average of 50, the Indian students, 53, and the White students, 56 (P <.001). On the 1993 US norms, Africans were at the 41st percentile, Indians at the 55th, and Whites at the 75th, with IQ equivalents of 97, 102, and 110, respectively. The African-Indian-White differences were most pronounced on those items with the highest item-total correlations, indicating a difference in g, or the general factor of intelligence. Hence, they were "Jensen Effects." Indeed, the g loadings showed a small degree of cross-cultural generality; for example, item-total correlations calculated on the Indian students predicted the magnitude of the White-African differences. When the 60 items were aggregated into 10 "subtests," the magnitude of the Jensen Effect was similar to that from previous studies based on whole subtests (median ρ=.53). There were no sex differences. Nor did this study of African engineering students support the idea of a bimodal distribution. © 2002 Elsevier Science Inc. All rights reserved.
