Posted on May 30, 2021

How to Explain the Black-White IQ Difference?

Hippocrates, American Renaissance, June 2010

The lower IQs of blacks compared to whites were first demonstrated in the United States in 1917 when soldiers drafted into the Army were tested for intelligence, and it was found that the black average was 83 compared to the white average of 100. This result has been confirmed in many hundreds of later studies, with black-white IQ differences typically between 15 and 17 points. This means about 15 percent of blacks have an IQ higher than the average white (or a little fewer, because many studies have found that black scores are not as broadly distributed as those of whites). Blacks who have high IQs tend to have whiter skins and other markers of white ancestry, which gives them more white genes for IQ. This is obvious from such public figures as Colin Powell, Jesse Jackson, Condoleezza Rice, Barack Obama, and Oprah Winfrey.

At the lower end of the IQ distribution, about 2 per cent of whites and about 16 per cent of blacks have IQs below 70, the threshold for mental retardation. Charles Murray and the late Richard Herrnstein showed in their 1994 book The Bell Curve that these IQ differences do much to explain why, on average, blacks do poorly in school, college, and employment, and are over-represented among single mothers and those on welfare.

Ever since this IQ difference was demonstrated there has been debate about whether the causes are genetic, environmental, or some mixture of the two. In recent years, James Flynn, emeritus professor at the University of Otago in New Zealand, has been the leading advocate of the environmentalist case, while Professors Philippe Rushton and Arthur Jensen have argued the hereditarian position. Before he emigrated from the United States to New Zealand in 1963, Professor Flynn took part in civil rights marches, and he continues to be active in leftist causes. He has now spent the last 30 years trying to prove that the black-white IQ difference is determined wholly by environment. This is a formidable task, given the huge amount of evidence favoring a genetic basis, including the smaller average black brain size, the fact that black infants adopted by white families do not register IQ gains, and the universally observed low black IQ throughout the world.

Nevertheless, Professor Flynn leaves no stone unturned to promote his case. In his 2007 book What is Intelligence? he asserted that “there have been thousands of blacks of genius or talent,” and cited Saint Augustine, Victor Hugo, Paul Robeson, and Thomas Sowell as examples. This is hardly a persuasive list. Saint Augustine was born in North Africa and was of Berber (North African Caucasoid) descent. Photographs of Victor Hugo suggest he was pure Caucasian without a hint of Negroid features. Paul Robeson was certainly a black singer of talent, but singing does not require a high IQ. Thomas Sowell is a black political scientist of some talent who clearly has some white ancestry. This bizarre quartet are apparently the best examples of black genius and talent that Professor Flynn can muster.

Professor Flynn has also sought to support his contention that the causes of the black-white IQ difference are environmental by maintaining that the American black-white IQ gap has been declining in recent years, and that between 1970 and 1992 the gap decreased by 5.5 IQ points. He contends that this narrowing can be projected into the future and that in the fullness of time will be closed completely, and blacks will have the same average IQ as whites. When this time comes, people will look back and realize that the low black IQ was entirely due to discrimination by racist whites.

Professors Rushton and Jensen have refuted Professor Flynn’s contention that the American black-white IQ gap has been narrowing in recent years. They show that from 1917 to 2008 there has been no black gain in average IQ, and also that from 1954 to 2008 there has been no gain in average black educational achievement measured by math and reading in the National Assessment of Educational Progress studies.

Professors Rushton and Jensen propose that the black-white IQ gap in the United States is about 80 percent genetically determined. They argue that it is widely accepted that the heritability of intelligence within races is between 50 and 70 percent, and that the heritability of the intelligence difference between blacks and whites is about the same or even higher. Certainly, it is inconceivable that it could be zero. If their 80 percent estimate is accurate, it means that if blacks could be given all the environmental advantages of whites, the black-white IQ gap could be reduced to 80 percent of its present value, i.e. to about 13 IQ points.

Professors Rushton and Jensen accept that the IQs of both blacks and whites have increased since the 1930s, but they produce evidence that the g component of intelligence has not increased at all. Intelligence can be divided into g and non-g components. G is the “general factor” that is a partial determinant of performance on all cognitive tasks. The non-g components consist of other abilities that are independent of g (e.g. reasoning, verbal comprehension, spatial ability, memory, etc). The professors used a statistical technique to measure both the g and the non-g components of intelligence and concluded that it is only the latter that have increased, probably as a result of improvements in education, health, and nutrition. This is a novel and interesting finding with regard to the Flynn effect, though some scholars have reservations about the methodology used, and remain skeptical about how accurately g can be separated from non-g components. Professors Rushton and Jensen also demonstrate that the tests whose results are most heritable produce the largest black-white IQ differences, showing that the stronger the genetic input, the greater the black IQ deficit.

The conclusion that the black-white IQ gap has not declined since 1917 is a serious problem for environmentalists. The environments of American blacks have improved greatly since 1917, with the achievement of higher living standards, better health care, integrated schooling, full civil rights, and affirmative action. The environment of whites has also improved, but that of blacks has certainly improved more.

So why has the gap not been reduced? Perhaps Professors Rushton and Jensen may have underestimated the genetic contribution to the black-white IQ gap when they put it at 80 percent. If the gap has not declined since 1917, it means it is resistant to environmental improvements and may be entirely genetically determined. If it is possible to reduce the black-white IQ gap no one now knows how this can be done.

Professor Flynn has yet to answer these points but he is a tenacious advocate of lost causes and we have probably not heard the last from him.

Flynn, J.R. What is Intelligence? Cambridge University Press, 2007.

Rushton, J. P., & Jensen, A. R. (2005). Thirty years of research on race differences in cognitive ability. Psychology, Public Policy, and Law, 11, 235-294.

Rushton, J. P., & Jensen, A. R. (2010). The rise and fall of the Flynn effect as a reason to expect a narrowing of the Black-White IQ gap. Intelligence, 38, 213-219.