Commenter Mugabe writes:

black Africans today and whites in 1900 scored the SAME. AND present day Africa is A LOT shittier IN EVERY WAY than 1900 in the West.

If what Mugabe is asserting here is true, then according to the Phenotype = Geneotype + Environment model, blacks must have a higher genetic IQ than whites, because given an inferior environment, they have an equal phenotypic IQ. But is Mugabe’s assertion true?

According to scientist Richard Lynn, on a scale where the white mean in Britain is set at a 100, “studies of the most satisfactory representative samples on the Standard Progressive Matrices give an IQ of 66” for black Africans. Of course Richard Lynn’s claim is controversial, but that’s a whole other topic. For the sake of argument, let’s take the IQ 66 figure as the best estimate of today’s black Africa’s IQ.

How does this compare to how whites scored in 1900?

In one study (see figure 2) the top 10% of British people born in 1877 (by definition those with IQ’s above 120 for their era) performed the same on the Raven as the bottom 5% of British people born in 1967 (by definition those with IQ’s below 75 for their era). In other words, performance on the Raven had increased by the equivalent of 45 IQ points in less than a century! Of course it wasn’t a level playing field because those born in 1877 took the test when they were a somewhat elderly 65 while those born in 1967 took the test when they were young sharp 25 year olds, however Flynn cites longitudinal studies showing that Raven type reasoning declines by no more than 10 points by age 65. That still leaves us with 35 points to explain.

Another source of inaccuracy was that although the test was not timed for either group, those born in 1877 took the test supervised while those born in 1967 got to take the test home. This could potentially make a large difference; not necessarily because the unsupervised group would cheat, but because they would probably take more breaks since they were in the comfort of their homes. They would probably return to challenging items after they had time to relax and see those items from a fresh perspective, while those who took the test supervised in some strange room were probably more likely to rush through the tasks so they could go home. I would estimate that being allowed to take an test home improves test performance by about 5 IQ points on average, though this is just a guess.

But that still leaves a huge difference of 30 IQ points. In other words, by the standards of modern British whites, whites born in 1877 had IQs of 70 (only 4 points higher than blacks score in sub-Saharan Africa today).

Correcting the IQs of Victorian whites for years of schooling

But it’s important to note that the British born in 1877 probably completed no more than eight grades of schooling on average, while modern whites average more than 12 years of schooling, and not attending high school may reduce IQ scores (though probably not real intelligence) by 8 points. It may seem unlikely that schooling could influence a test that seems as culture fair as the Raven, but some people argue that the Raven is actually culturally biased. Richard Lynn argues that it requires basic math skills like addition and subtraction and believes the rise in education explains part of the adult Flynn Effect. At the very least, people with more schooling might be more likely to take the test from a mathematical perspective or with more motivation, confidence, and persistence. So correcting for their lack of schooling raises the IQs of British Victorians from 70 to 78.

Correcting the IQs of modern black Africa for years of schooling

Black Africans also achieve much less schooling than modern whites, however the Black Africans who are typically tested in Raven IQ studies are school children, so the years of schooling variable is already controlled. Thus their IQ of 66 can not be increased by correcting for years of schooling.

Correcting the IQs of Victorian whites for nutrition

What about the biological environment? Whites born in 1877 were 1.5 standard deviations shorter than whites today. If we make Richard Lynn’s assumption that nutrition (including disease which limits the body’s ability to use nutrients) affects IQ to the same degree it affects height, then correcting for nutrition further raises the IQs of white Victorians from 78 to 101 (an increase of 1.5 SD). So correcting for just the two most obvious environmental variables (years of schooling and nutrition) brings white Victorians up to the level of modern whites.

Correcting the IQs of modern black Africa for nutrition

Black Africans today are also malnourished as evidenced by modern West Africans being 0.8 SD shorter than modern African Americans. Correcting their IQ for this 0.8 SD deficit raises them from 66 to 78. This is somewhat lower than the average IQ of 85 for African Americans, but keep in mind that the average African American has as much as 25% white ancestry and whites average around IQ 100. Based on these stats, Richard Lynn calculates that African Americans with no white ancestry have IQs around 80.

So after correcting for very simple and obvious environmental deficits, blacks reared in the third World have the same IQs as their genetic counterparts reared in the First World for centuries.

Conclusion

This demonstrates that a simple Phenotype = Genotype + Environment model can work well for group differences, with environment defined simply as years of schooling + nutrition. This simple model seems to explain both the Flynn effect, and IQ differences between blacks in the Third World and blacks who have lived in the First World for centuries.

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