Richard Nisbett on IQ and Race

If there has been at least one good side-effect of Dr. Watson making a jack-ass of himself, it is that it has given scientists the opportunity to set the record straight about heredity, race, and IQ. (He has since recanted, so everything is all better now. Watson to Blacks: "Sorry Blacks." Blacks to Watson: "Um...apology not accepted.")

Richard Nisbett clarifies the issue superlatively in the NYTimes:

The hereditarians begin with the assertion that 60 percent to 80 percent of variation in I.Q. is genetically determined. However, most estimates of heritability have been based almost exclusively on studies of middle-class groups. For the poor, a group that includes a substantial proportion of minorities, heritability of I.Q. is very low, in the range of 10 percent to 20 percent, according to recent research by Eric Turkheimer at the University of Virginia. This means that for the poor, improvements in environment have great potential to bring about increases in I.Q.

In any case, the degree of heritability of a characteristic tells us nothing about how much the environment can affect it. Even when a trait is highly heritable (think of the height of corn plants), modifiability can also be great (think of the difference growing conditions can make).

I will say it again. (I am contemplating a program of educational tattoos as well.)

Heritability is not the percentage of a trait that is genetic. Heritability is the variance around the population mean that can be attributed to genetic as opposed to other causes. This population mean can still change due to environment, ergo high heritability does not imply genetic destiny.

This is another critique of the race equals differences in IQ idea. The other is of course that heritability in IQ varies widely depending on the group you are measuring and has changed over time -- the Flynn effect.

Further, as Nisbett argues, there is considerable evidence for environmental effects on IQ:

During World War II, both black and white American soldiers fathered children with German women. Thus some of these children had 100 percent European heritage and some had substantial African heritage. Tested in later childhood, the German children of the white fathers were found to have an average I.Q. of 97, and those of the black fathers had an average of 96.5, a trivial difference.


A superior adoption study -- and one not discussed by the hereditarians -- was carried out at Arizona State University by the psychologist Elsie Moore, who looked at black and mixed-race children adopted by middle-class families, either black or white, and found no difference in I.Q. between the black and mixed-race children. Most telling is Dr. Moore's finding that children adopted by white families had I.Q.'s 13 points higher than those of children adopted by black families. The environments that even middle-class black children grow up in are not as favorable for the development of I.Q. as those of middle-class whites.

Read the whole thing.

There has been a lot of shamefully bad journalism associated with this subject. Exhibit A: William Saletan at Slate's defense of Watson which the Lede blog interestingly refers to as "an academic defense." (This of course begs the question whether you need to understand a subject to academically defend it? In the Lede's view, apparently not. I am willing to write that comment off to professional courtesy.)

This bad journalism, I think, can be nearly exclusively attributed to the fact that people don't understand what the term heritability means. Which just means that we will have to keep correcting them. Oh well...

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the rate of rejection based on IQ tests by the US Armed Forced during WWII was twice as high for blacks as for whites. So the samples of white and black soldiers were different to begin with.

I am continually amazed by those who would point to the environment and culture as sufficient explanations for racial differences in IQ. Unless one accepts that cultural factors are themselves rooted in heritable biological differences, there is an infinite explanatory regress. Where does culture come from, if not, in part, from biology?

By doublehelix (not verified) on 10 Dec 2007 #permalink

culture comes from ancestral norms, i.e music is an example. the slight difference of the european babies just points to the armys restriction on entrance, the men scored equally, hence their babbies would scored closely as to the limited varience off enviroment. thus enviroment has a closer relationship to intelligance than heredty.

By karl roenfanz … (not verified) on 12 Dec 2007 #permalink

I sho do lak dem G-nomes.

By Lance Pierre (not verified) on 16 Dec 2007 #permalink

I wonder why some brothers and sisters are much smarter than other brothers and sisters when within the same family all things were equal (attention, comfortableness, education, etc.)?
Respectfully submitted, I AM
William Roger Jones
Jeju Island

By William Roger Jones (not verified) on 20 Dec 2007 #permalink

***I am continually amazed by those who would point to the environment and culture as sufficient explanations for racial differences in IQ.***

When surveyed privately, only a small minority of behavioural geneticists or psychologists actually believe that - far more consider environmental and genetic variation causes the gaps (see the Snyderman & Rothman survey).

This is a rather dense post, but typical. Why don't we start with what Watson said: "[I am] inherently gloomy about the prospect of Africa [because] all our social policies are based on the fact that their intelligence is the same as ours â whereas all the testing says not really.â And then he suggested that there COULD be a genetic basis to the difference.
And then he "recanted" by clarifying that he was not implying that Africans were inferior, just that 1) the testing shows that Africans do poorly on measures of intelligence and 2) there COULD be a genetic basis to the difference. What did he say that was incorrect?

Your point about heritability is irrelevant. Heritability estimates establish that there is a substantial genetic component to general intelligence differences between individuals. This means that there COULD be a genetic component to general intelligence differences between groups. Your point about the Flynn effect is also irrelevant. There is no evidence that the Flynn effect represents a rise in general intelligence. Multigroup factor analysis shows that strict measurement invariance does not hold between cohorts, implying that the difference between cohorts is of a different nature (e.g. a product of test familiarity) than the substantially genetic differences within cohorts. Of course, differences between some groups might be like the differences between cohorts but they COULD also be like the highly genetic differences between individuals. As for Nisbett, he doesn't exactly provide a balanced review. But then neither do you.