Friday, May 22, 2009

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.


  1. Anonymous5:14 PM

    Astonishing to see it all laid out like that. The size of the IQ differences are suprising even to me. I guess selection pressures really do account for much. m

  2. I babysat and had a paper route at age 10 and started driving and hunting when I was 13. So in other words you lived in a 10-year-old's hell and a 13-year-old's paradise.... :)

    There was a lot of talk about this at iSteve, but I couldn't quite make out one of the critiques. You should visit if you have time.

  3. The average is as low as 54 for some groups? I had no idea the gaps were so huge.

    Koko the gorilla, by the way, reportedly "has a tested IQ of between 70 and 95 on a human scale." That's a pretty wide margin of error (nearly two SDs), but still. The more I learn about human biodiversity, the more sense the animal rights movement makes.

  4. Anonymous8:26 PM

    "Koko the gorilla, by the way, reportedly "has a tested IQ of between 70 and 95 on a human scale."

    I would be curious to know the design of these "IQ" tests... and how they guarded against the Clever Hans Effect.

  5. Anonymous8:34 PM

    ...Keeping in mind that Penny Patterson, Koko's primary handler and interpreter, is deeply, deeply in love with Koko.

  6. Anonymous7:36 AM

    So as a Black parent, you basically should not have high aspirations for your child despite high childhood test scores. Right now I am pushing my child toward the Ivy league but these show his Iq is going to drop when he is an adult so I should just not waste my time.

    Its really depressing to see that no matter how hard you work, your children are basically screwed. I guess most of you guys will jump for joy.

  7. Edward9:24 AM

    "Its really depressing to see that no matter how hard you work, your children are basically screwed."

    Use your window of opportunity wisely. Your powers as a parent will drop sharply once the child moves out of the house. (Suprise!) The point of parenting is to get your child on the right track -- or at least steer them clear of the wrong one.

    Here is an example of what happens when you combine the right stuff with the wrong parenting:

  8. Right. The long-term impotency of parents is not limited to blacks. Whites have the same problem. One obvious (but not easy) thing parents can do is raise the money to send your child to the best school he can get into.

  9. I want Americans black and white to be a smart as they can be, but wishful thinking isn't going to help.

  10. Anonymous2:42 PM

    well that comment was sort of unnecessary self-pity. My son consistently tests in the mid 130's, so if he ends up in 120's its not really that bad.

    Actually I have gleaned some valuable info from you HBD lot. Especially in understanding the strong influence of peers.

  11. Edward7:54 PM

    The fact that you are a black father who is concerned enough about the well being of his son to hang around HBD blogs is a strong sign that your child comes from good stock. Consider your odds a bit better than self pity would warrant.

    120 is actually a sweet spot: smart enough to relate to most people, but not so smart that you fall off the Nerd Cliff. Lots of executives clock in at around 120.

    If he is 130 now and a little nerdy, that might actually help insulate him from some of the more toxic elements of the culture until he makes it to adulthood.

  12. Thanks for the link, Edward. His is an interesting story. I'd love to be friends with someone like him.

    As far as right path vs. wrong path, I'd say that the right path is what will eventually make the child into a happy, healthy adult. That path is slightly broader for an average IQ child than a high or low IQ child. While we used to think a parent needed to work to make their child:
    sociable (this doesn't mean extroverted! pet peeve of mine)
    ... now we have a list that is shorter by one item.

    That is the way I see it. Getting your children enough books with big words them isn't half or a tenth as important as delivering them a sensible world-view, a capacity to self-assess and self-correct, a respect for others, etc. My two bits.

  13. Edward9:18 PM

    "Thanks for the link, Edward."

    I don’t mean to paint Langan as a disaster story. You could do worse. But it is hard to deny that with a little better guidance, he could be contributing more to society and his everlasting reputation.

    He seems reasonably happy though -- all be it a little wacky -- which suggests that a high IQ can preserve you through a crappy upbringing.

  14. He seems reasonably happy though -- all be it a little wacky -- which suggests that a high IQ can preserve you through a crappy upbringing.It surely can, and it can preserve you in a bad way as well as a good way. Big and intimidating, Langan could have ended up in some criminal organization, maybe keeping books like the folks mentioned in Freakonomics (a fun read despite the inaccuracies Steve Sailer has highlighted). Langan, of course, has about 80-100 surplus IQ points to be a bookkeeper, but you get the point.

    Langan indeed shepherded himself through some tough times. I was reminded of Moldbug when he said the high IQ community could be an alternative to academe when it comes to civic leadership and sage wisdom. (Moldbug talks more about standardized tests in general than IQ tests specifically, but I think they're on the same page, especially considering the huge number of things IQ correlates with.)

  15. "So as a Black parent, you basically should not have high aspirations for your child despite high childhood test scores. Right now I am pushing my child toward the Ivy league but these show his Iq is going to drop when he is an adult so I should just not waste my time."

    These statistics are just averages. Plenty of blacks have what it takes to do well in the Ivy League, and there's no reason why your son shouldn't be one of them. Population statistics should be used to think about populations, not to jump to conclusions about individuals.

  16. Anonymous8:16 AM

    What is the difference between IQ and g, and how do you isolate the two?

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