Bell Curve

720 Notes to pages 289-292 Notes to pages 292-293 72 1their separate reviews of the literature, Audrey Shuey (whose review waspublished in 1966) and John Loehlin and his colleagues (review publishedin 1975) identified thirteen studies conducted from 1948 through the early1970s that resented IQ means for low- and high-SES groups by race. Intwelve of the thirteen studies, the black-white difference in IQ was higherfor the higher-SES group than for the lower-SES group. For similar resultsfor the 1981 standardization of the WAIS-R, see Reynolds et al. 1987. Afinal comment is that the NLSY also shows an increasing B/W differenceat the upper end of the socioeconomic scale when the 1980 AFQT scaringsystem is used and the scores are not corrected for skew. See Appendix2 for a discussion of the scoring issues.44. Kendall, Verster, and Mollendorf 1988.45. Kendall, Verster, and Mollendorf 1988. For another example, this time ofan entire book devoted to testing in the African setting that fails to mentiona single mean, see Schwarz and Krug 1972.46. Lynn 199 1c.47. Boissiere et al. 1985.48. Owen 1992.49. Reynolds et al. 1987.50. Vincent 1991.5 1. Vincent also cites two nonnormative studies of children in which the R/Wdifferences ranged from only one to nine points. These are the differencesafter controlling for SES, which, as we explain in the text, shrinks the A/Wgap by about one-third.52. Jensen 1984a; Jensen and Naglieri 1987; Naglieri 1986. They point outthat the K-ARC test is less saturated with g than a conventional IQ measureand more dependent on memory, both of which would tend to reducethe B/W difference (Naglieri and Bardos 1987).53. Jensen 1993b.54. Rased on the white and black SDs for 1980, the first year that standard deviationsby race were published.55. Wainer 1988.56. Our reasons for concluding that the narrowing of the B/W differences onthe SAT was real, despite the potential artifacts involved in SAT score, areas follows. Regarding the self-selection problem, the key consideration isthat the proportion of blacks taking the test rose throughout the1976-1993 period (including the subperiod 1980-1993). In 1976, blackswho took the SAT represented 10 percent of black 17-year-olds; in 1980,the proportion had risen to 13 percent; by 1993, it had risen to about 20percent. While this does not necessarily mean that blacks taking the SATwere coming from lower socioeconomic groups (the data on parental edu-cation and income from 1980 to 1993 indicate they were not), the poolprobably became less selective insofar as it drew from lower portions of theability distribution. The improvement in black scores is therefore morelikely to be understated by the SAT data than exaggerated.Howard Wainer (1988) has argued that changes in black test scores areuninterpretable because of anomalies that could be inferred from the testscores of students who did not disclose their ethnicity on the SAT backgroundquestionnaire (nonresponders). Apart from several technical questionsabout Wainer's conclusions that arise from his presentation, the keypoint is that the nonresponder population has diminished substantially. Asit has diminished, there are no signs that the story told by the SAT is changing.The basic shape of the falling trendline for the black-white differencecannot plausibly be affected by nonresponders (though the true means inany given year might well be somewhat different from the means based onthose who identify their ethnicity).57. The range of .15 to .25 SD takes the data in both the text and Appendix5 into account. To calculate the narrowing in IQ terms, we need to estimatethe correlation between IQ and the various measures of educationalpreparation. A lower correlation would shrink the estimate of the amountof 1Q narrowing between blacks and whites, and vice versa for a higher estimate.The two- to three-point estimate in the text assumes that this correlationis somewhere between .6 and .8. If we instead rely entirely on theSAT data and consider it to be a measure of intelligence per se, then thenarrowing has been four points in IQ, but only for the population that actuallytakes the test.58. A change of one IQ point in a generation for genetic reasons is not out ofthe realm of possibility, given sufficient differential fertility. However, theevidence on differential fertility (see Chapter 15) implies not a shrinkinghlack-white gap but a growing one.59. Jaynes and Williams 1989; Jencks and Peterson 1991.60. Linear extrapolations are not to be taken seriously in these situations. Alinear continuation of the black and white SAT trends from 1980 to 1990would bring a convergence with the white mean in the year in 2035 onthe Verbal and 2053 on the Math. And when it occurs, racial differenceswould not be ended, for if we apply the same logic to the Asian scores, inthat year of 2053 when blacks and whites both have a mean of 555 on theMath test, the Asian mean would be 632. The Asian Verbal mean (again,based on 1980-1990) would be 510 in the year 2053, forty-seven pointsahead of the white mean. But-such is the logic of linear extrapolationsfrom a short time ~eriod-the black Verbal score would by that time havesurpassed the white mean by thirty-seven points and would be 500, only