Although the vast majority of studies suggest that the black-white IQ gap has been about 15 points for the last 100 years, a major outlier in the data was the mass testing that occurred during WWII where the black-white IQ gap jumped to a record high of 22 points.  On a scale where U.S. whites average 100, U.S. blacks averaged a disastrous 78, instead of the more typical 85 they’ve been average since WWI.

Charles Murray’s theory

This mysterious outlier has inspired two very different theories.  Scholar Charles Murray argued that black IQ only became 85 after WWII, and that in the first half of the 20th century it was 78 because of the abysmal environment blacks suffered during that era.  He dismissed the IQ of 85 found in WWI as sampling error, arguing that WWI excluded many of the 70% of African Americans who lived in the rural South and had little or no schooling.  Why rural Southern blacks would be excluded is a question Murray ignores.

Rushton and Jensen’s theory

Piggybacking on Murray’s theory, scholars J.P. Rushton and Arthur Jensen came up with a terrifying theory.  They agreed with Murray that the black IQ might have been 78 during the first half of the 20th century, however unlike Murray, they didn’t stop there.  They argued that the black IQ might still be 78, and that low IQ blacks are still being excluding from studies because today they live deep in the inner city where professional testing seldom takes place.  The WWII testing was perhaps the most representative sample of U.S. blacks ever tested so it was the rare case where the low IQ segment was included.

Although I love the idea of a secret black underclass that is so dysfunctional, psychologists are afraid to test them, I don’t think this is the case.  For starters, this underclass would probably need to have an average IQ around 70 to drag the entire black average down from 85 to 78 and I don’t think such a low IQ black underclass exists in the U.S..  Even homeless blacks average IQs around 80, and the homeless seem like the lowest of the low.

Secondly, the sampling done by the WAIS-IV is far too meticulous to have overestimated the black IQ to such a large degree.  The blacks they include in their norms must have the same distribution of education and occupational status as blacks in the U.S. census, so it’s very hard to see how a large class of super low IQ blacks could be systematically excluded.

Pumpkin Person’s Theory

So how do we explain why blacks scored IQ 78 in the mass testing in WWII but have averaged 85 before and since.  My theory is that it’s because the WWII testing was not an official IQ test like the Army Alpha or the WAIS, but a test of crystallized academic knowledge like the SAT.  I believe these tests are especially sensitive to the cultural environment so in the first half of the 20th century, when blacks attended segregated schools, they were especially penalized on a test calling for academic knowledge, especially one like the Army General Classification Test which emphasizes mechanical knowledge (since blacks tend to do worst on spatial tasks).  Bill Cosby, the high IQ centimillionaire who got a combined SAT of only 500, is an example of how even very bright blacks from that era performed disastrously on achievement tests.

“I had never studied,” joked Cosby. “Anything!”

Despite his abysmal SATs, Cosby attended a school for the gifted.

“You’re very smart,” folks would say.

“YES I AM!” Cosby would shout.

“Well do you know anything?”

“NO I DON’T” Cosby replied.

So I agree with Murray that blacks performed worse on mental tests in the first half of the 20th century, but unlike Murray, I believe this was only true of achievement tests like the SAT, AGCT and ASVAB.  On actual IQ tests, blacks have performed consistently at about 85 for the last 100 years.

This is yet another example of how ACTUAL IQ tests are superior measures of innate ability compared to achievement tests.