Will the developing world attain mean IQs that match those of the developed world in the foreseeable future? There is no doubt that a significant IQ gap between the two exists. Lynn and Vanhanen (2002, 2006) recorded it and suggested that the developing world does not have the intelligence to equal the record of the developed world for economic growth. I suspect it is not that simple. In 1917, Americans had a mean IQ of 72 (against today’s norms) and a good estimate for 1900 would be 67. Only two developing nations fall significantly below this (Saint Lucia and Equatorial Guinea). The US did not leap from 67 to 100 as a prerequisite for industrial development; rather it was a matter of reciprocal causality. The first step toward modernity raised IQ a bit, which paved the way for the next step, which raised IQ a bit more, and so on. It was like climbing a ladder: start with one foot, next step up with the other foot, until you reach the top.

First, I will argue that the evidence that inferior genes for intelligence handicap the developing world is suspect. Second, I will note something unexpected: the IQ gains of the developed world seem to be persisting into the twenty-first century. If this continues, it will be more difficult for the developing world to catch up. Third, I will show that even so, the developing world has the potential to gain at a faster rate. Malnutrition, inbreeding, and ill health are present there and, if overcome, promise dividends. By contrast, these factors have had little effect on IQ in the developed world since 1950. Fourth, I will give evidence that IQ gains in the developing world have begun.

Box 6 in Chapter 3 gives estimates for gains over time on certain WISC and WAIS subtests and projects those gains into the future (up to 2012). It is derived from four tables.

(1) Table AI1 gives WISC gains on all subtests from the WISC (1947.5) to the WISC-IV (2001.75). Table AII3 in Appendix II adds detail on the calculations.

(2) Table AI2 uses past trends to project the gain from the WISC-IV to the “WISC-V” on the assumption that the latter will be normed in 2012. This entails pro-rating all subsequent trends over the interval of 24.5 years that separated the norming of the WISC and WISC-R. All calculations are explained at the bottom of the table. The final column gives what I think the actual ScaledScore gains (SD = 3) will be from the WISC-IV to the WISC-V, just for fun. To get the modern age values in Box 6 , average the four Modern world values numbered (1) to (4) respectively.

(3) Table AI3 gives WAIS gains on all subtests from the WAIS to the WAIS-IV. Table AII2 in Appendix II adds detail on both scores and calculations.

(4) Table AI4 uses past trends to project the gain from the WAIS-IV to the “WAIS-V” on the assumption that the latter will be normed in 2016. This entails projecting all subsequent trends over the interval of 24.5 years that separated the norming of the WAIS and WAIS-R. All calculations are explained at the bottom of the table. The final column gives what I think the actual Scaled Score gains (SD = 3) will be from the WAIS-IV to the WAIS-V, just for fun. To get the modern age values in Box 6 , average the four Modern World values numbered (1) to (4) respectively.

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.

Some thirty-five years ago, I began my periodic visits to the field of psychology. Over time, I became uneasy about something that seemed both odd and crippling: the isolation of the study of intelligence from an awareness of the social context within which all human behavior occurs. Many psychologists are happy to infer the social consequences of what they learn about intelligence. But all the causal arrows tend to run one way: they do not infuse their study of intelligence with social awareness.

Over 50 years ago, C. Wright Mills (1959) published The Sociological Imagination. The sociological imagination is the ability to see people socially and take into account how they interact and influence each other. I will emphasize a facet of the sociological imagination: always asking what social behavior lies behind measurements and models. To illustrate what happens when social awareness recedes into the background, I will offer 14 examples.

The mystique of the brain

Students of intelligence look forward to the day when all cognitive behavior can be explained in terms of brain physiology. But if they become obsessed by that task, they forget that understanding brains is only part of understanding human intelligence. Jensen (2011) is worth quoting at some length.