Race and gender IQ differences arouse strong emotions and therefore I excluded them from What Is Intelligence? I did not want critical assessment of my views on intelligence lost in a welter of acrimonious debate. Look at what happened to The Bell Curve, which was 90 percent about other subjects and debated as if it were 90 percent about race.

I have offered my case that the black/white IQ gap is probably environmental in origin elsewhere (Flynn, 1980, 2008), and will not repeat it here. However, much of this book preaches the message that differences between Wechsler subtests are central to interpreting IQ trends. The following will, I hope, show that these subtest differences are not central to the race and IQ debate, at least not for the reasons given by thinkers such as Jensen and Rushton. As a bonus, we may enhance our understanding of why WISC subtests differ in a variety of ways: not only in the size of the black/white performance gap, but also in terms of their g-loadings, heritability, and sensitivity to inbreeding depression.