Race differences in IQ: For those of you who don't have the time to read Rushton and Jensen's 50 page review of Nisbitt's Intelligence and How to Get It, I outline the points I found interesting below. It's funny how the research literature is this rich and advanced (compared to, say, educational research work in the area) but the typical mainstream position is that IQ research is way too crude and undeveloped to inform policy. One frickin' doll study helped decide Brown v. Board of Education, but a century of research by psychometricians shouldn't even give us pause.


1. World IQ is 90: East Asian cluster is 105, Europeans are 100, Inuit-Eskimos 91, SE Asians 87, Native Americans 87, Pacific Islanders 85, South Asians and North Africans 84, sub-Saharan Africans 67, Australian aborigines 62, and Kalahari Bushmen and Congo Pygmies 54.

2. Flynn effect: IQ has increased in the developed world in the last 50 years, and the black-white gap has narrowed a bit. The gain is not on g which is in large part genetic.

3. Research was cited suggesting that the IQ gap is larger than 15 points because a disproportionate number of low IQ blacks do not make it into samples.

4. Research shows that the Flynn effect is qualitatively different from black-white differences in regards to the g factor.

5. A test's g loading is the best predictor of biological measures of heritability coefficients determined from twin studies, inbreeding depression scores calculated in children of cousin-marriages, brain evoked potentials, brain pH levels, brain glucose metabolism, as well as nerve conduction velocity and reaction time measures. The correlations argue strongly for the biological, as opposed to the mere statistical reality of g.

6. Across 149 psychometric tests, the correlation between g-loading score and black-white difference is .62. This contradicts the culture-only theory.

7. Research indicates that there is no factor lowering IQs that is specific to blacks.

8. The correlation between several measures of reaction times and IQ is .6. Asians are faster than whites, and whites are faster than blacks. The differences are not due to motivation: while Asians and whites react faster, blacks move faster.

9. Heritability is lowest early in life and rises to 60-80% by adulthood. Shared environment falls to 0% by adulthood. Adoption can raise the IQ of a child quite a bit, but g remains like that of the biological parents.

10. The model that best fits data from a sample of black and white twins is 50/50 genes and environment.

11. Non-hereditarians like Robert Sternberg get results like those reported by Lynn when they administer IQ tests to sub-Saharan Africans. Even after training kids how to solve problems like those on the test, means were under 80. Teaching to the test denudes the test of its g loading. Studies of Africans who have won math and science competitions put mean IQ at 100. African IQs predict academic and job performance as well as for non-Africans. With a white mean set at a mental age of 16, an African mean of 70 implies a mental age of 11. Eleven year olds are not retarded. (I babysat and had a paper route at age 10 and started driving and hunting when I was 13.)

12. In a MRI study, Posthuma et al. found heritabilities of 82 percent for whole-brain gray matter volume, 87 percent for whole-brain white matter volume, and 86 percent for IQ.

13. Smaller black brain sizes do not appear to be due to prenatal or perinatal conditions. In a study of fetuses, Schultz found that from the 9th week of intrauterine life, 165 Black fetuses averaged a smaller brain case than did 455 White fetuses. The difference became more prominent over the course of fetal development.

14. In meta-analyses of general population samples on the Progressive Matrices, Lynn and Irwing found no sex difference in IQ among children aged 6- to 14-years but a male advantage from 15-years through old age, with the male advantage by adulthood being equivalent to about 4.6 IQ points.

15. Winick et al. studied 141 Korean children malnourished-in-infancy and then adopted as infants by American families. They found that by 10 years of age the children exceeded the national average in IQ and achievement scores: A severely-malnourished group obtained a mean IQ of 102; a moderately-nourished group obtained a mean IQ of 106; and an adequately-nourished group obtained a mean IQ of 112.

16. Regression to the mean effects support hereditarian theory. The IQs of the siblings of blacks with 120 IQs is 100; for their white counterparts it is 110. It is the same on the low end: when blacks and whites are matched at an IQ of 70, black siblings average a 78; the white siblings, an 85. This helps to explain why Black children born to well-educated, affluent, parents have test scores 2 to 4 points lower than do White children born to poorly-educated, impoverished parents.