An essay on race and intelligence

Found this over at Half-Sigma.

The James Watson controversy has gotten me thinking about the black-white intelligence difference. As you know, it is well documented that, in the United States, the average black person scores about one standard deviation below the average white person on all variety of mental tests, including self-named IQ tests, the SAT, the reading and math competency tests given to school children, and pre-employment tests. For those who don’t understand the term “standard deviation,” here’s a simple example: if there is a one standard deviation difference between whites and blacks, that means that only 16% of blacks will score equal to or higher than the score of the average white person, and only 16% of whites will score equal to or below the score of the average black person.

The politically correct chorus screams very loudly that the observed intelligence difference is due to environment, the environment being discrimination, poor schools, poor nutrition, and anything else they can think of to give weight to their argument. It’s obvious that the average black lives in a disadvantaged environment compared to the average white, but it’s not obvious that this proves anything. If the following three propositions are true:

(1) we live in a society where how much money one is able to earn is correlated with one’s intelligence;
(2) one’s intelligence is correlated with one’s parents‘ intelligence on account of genetic heredity;
(3) various genes that correlate with high intelligence occur less frequently in the black gene pool than in the white gene pool

then the expected result would be that the average black would live in a disadvantaged environment compared to the average white.

Proposition one above is obvious and doesn’t need much explanation. Everyone knows that college graduates earn more than high school dropouts. People who aren’t smart enough to do well on the SATs won’t get into college, and people who aren’t smart enough to read at grade level are more likely to drop out of high school in frustration. For readers looking for a more detailed examination of how low intelligence leads to poorer life outcomes, I recommend The Bell Curve by Herrnstein and Murray. It’s an excellent book that has been unfairly maligned, mostly by people who want to shoot the messenger. That said, it’s more of a sociology book rather than a scientific treatise on genes and intelligence, and Murray is often overeager to jump to conclusions, but nevertheless it’s an interesting and thought provoking book. (People who have been reading my blog for a while know that I’ve written many posts about how high intelligence isn’t as great a benefit as some think, but the point of those posts is not that intelligence doesn’t matter, but rather that low intelligence is a better predictor of poverty and other bad outcomes than high intelligence is a predictor of wealth and other good outcomes.)

Proposition two, that intelligence has a genetic component, has now become generally accepted, even though back in the 1970s the politically correct establishment was adamantly opposed to the idea. There has just been too much evidence to the contrary. Studies of identical twins reared apart, as well as various other kinship studies, demonstrate that intelligence as measured by IQ tests is 70% to 80% hereditary. To back up kinship studies, scientists are now discovering actual genes correlated with intelligence; on the other side of the country, different scientists discovered another gene correlated with intelligence.

So what about proposition three, that the genes that correlate with high intelligence occur less frequently in the black gene pool? One might start with the basic Occam’s Razor principle, that the simplest explanation is usually the correct one. Given that blacks score lower than whites on intelligence tests, and given that intelligence is a genetically determined hereditary trait, the simplest explanation is that the black-white intelligence difference is genetic. As pointed out at the beginning of this essay, the fact that the average black grows up in a disadvantaged environment relative to the average white doesn’t prove or disprove anything.

If I wanted to set up an experiment to best study the issue, this is what I would do: I would compare the intelligence of black children adopted by upper-middle-class white families to the intelligence of white children adopted by upper-middle-class white families. This ensures that all children being studied are brought up in the most favorable family environment, and therefore any difference that emerges between the groups is a result of genetics and not environment.

It turns out that the exact situation above has already been studied! I am referring to the Minnesota Transracial Adoption Study, and there is an excellent page at Wikipedia summarizing the results of the study. It’s rather ironic that the researchers who conducted this study were left-wing types who were hoping to prove that it’s environment, not genes, that causes the black-white intelligence difference.

In interpreting the results, I must note that it’s not clear what IQ test was being used, but I presume that the scoring scale follows the convention in the IQ field that the average score is 100, and the standard deviation is 15, and when such an IQ test is given to both whites and blacks, it’s expected that the average white person will score 100 and the average black person will score 85.

When IQ tests were given to adopted 7-year-olds, the average scores were:

White: 112
Half white, half black: 109
Black: 97

As predicted by the genetic explanation, black children scored 15 points lower than white children. And children of mixed race background scored between the two extremes. Yet strangely, Scarr and Weinberg, the authors of the study, argued that this somehow proves that it’s environment causing the black-white IQ difference. They said, “look, half-white half-black children, who are ‘socially black,’ score higher than the average white child when they have upper-middle-class parents!”

If we assume that this same test would show an average score of 100 for white kids raised by regular blue collar white parents, then the study is indeed showing an effect where being raised by upper-middle-class white parents has a strongly positive impact on IQ tests given to 7-year-olds. But the effect isn’t one where racial IQ differences are eliminated. Rather, the effect is that less-intelligent children get an average score on the test, and average children get an above-average score on the test. There is similar evidence from many other studies that early childhood test scores are more easily raised by coaching than tests given to teenagers and adults. This is what studies of the Head Start program have showed:

Children enrolled in Head Start enjoy significant, immediate gains in cognitive test scores, socioemotional test scores, and health status. In the long run, cognitive and socio-emotional test scores of former Head Start students do not remain superior to those of disadvantaged children who did not attend Head Start. [source]

I believe the reason for this is that IQ tests given to young children are obviously unable to test the full range of adult level thinking skills. They can only test a narrow subset of skills, and the enrichment activities given to young children are very similar to the types of questions on early-childhood IQ tests, so children are being trained or coached to do well on such tests. A dog who has learned to sit on command isn’t any smarter than the untrained dog, the trained dog has simply been taught a trick.

If you refer to the Wikipedia article for the results of the followup study when the children were 17, we see that the early effects of being raised in an upper-middle-class family have mostly worn off. At the age of 17, the black adopted children have a measured IQ of 89, while the white adopted children have a measured IQ of 106. High school class ranks show a similar effect. White adopted children had an average rank of 54th percentile, only slightly above average, while black adopted children had an average rank of 36th percentile. There still seems to be a small beneficial effect to being raised by upper-middle-class parents (and only crazy IQ-absolutists would think that there’s no benefit to having upper-middle-class parents), but that effect is independent of the black-white intelligence difference.

I view the Minnesota Transracial Adoption Study as conclusive enough proof, given all the other evidence out there, that proposition three above is the correct one, that various genes that correlate with high intelligence occur less frequently in the black gene pool than in the white gene pool.

It’s possible to write a whole book on this topic, but that would be a waste of my time because the book has already been written: it’s The g Factor by Arthur Jensen, and should be the starting point for anyone who wants to know more. And since the publication of The g Factor, there have been many new discoveries in genetics, as mentioned above, that add further evidence that Arthur Jensen was correct in all of his conclusions.

At the conclusion of this essay, it’s appropriate to ask if this essay will convince anyone of anything? The answer is that it’s possible that someone sitting on the fence would be swayed over to the correct side, but for the most part, human beings are amazingly adept at ignoring logic and reason when it suits them. Among educated white people, the idea of racial equality has become a religion, and the whole point of religion is that it involves faith rather than science. Just as there’s zero chance of using logic and reason to get a fundamentalist Christian to believe in evolution, there’s zero chance of using logic and reason to get a hardcore liberal to see the truth about racial intelligence differences. People who are capable of using logic and reason to solve a complicated math problem, for some reason, shut down when an application of similar reasoning would cause one of their core beliefs to be proved wrong. In general, people are much more comfortable in adopting the belief of the majority rather than making up their own minds. And it doesn’t seem to matter how nonsensical the majority beliefs are.

But my prediction is that beliefs will soon change. With the progress we are making in genetic research, within a decade or two, we will probably be able to identify a large number of genes that determine intelligence, and scientists will be able to develop a genetic test that is able to predict someone’s intelligence. This will prove once and for all that there are racial differences in intelligence. (And here’s a question for those who will inevitably leave angry comments on this post: what will it take to convince you that the black-white intelligence difference is genetic? Will a genetic IQ test do it?)

BIBLIOGRAPHY

Here's a link to a 60-page paper by two leading researchers documenting why race differences in intelligence are genetic: Thirty Years of Research on Race Differences in Cognitive Ability, by Rushton and Jensen. Obviously there's nothing I can say in my amateur blog post that can equal the quality of discourse in their paper, so I recommend reading it. It's free. It answers nearly all of the objections raised in the comments. And did I mention it's free?

RESPONSE TO COMMENTS

I have written a blog post responding to common criticisms of this essay and others like it.