The gap in IQ scores between whites and African-Americans has narrowed by at least a quarter since 1972, a pair of researchers contend in a new paper that attempts to skewer the argument that intelligence is a mostly inherited trait.
Researchers William T. Dickens and James R. Flynn analyzed 30 years of test-score data from four commonly used intelligence tests. From 1972 to 2002, they found, IQ scores rose for all groups, but scores for blacks rose faster. They gained 5 to 6 IQ score points more than whites did—an improvement the researchers characterize as considerable.
“We believe there’s been a real change,” said Mr. Dickens, a senior fellow in economic studies at the Brookings Institution, a Washington-based think tank. “And we suspect that it has something to do with improving conditions, at least for black youth and young adults.” His co-author, Mr. Flynn, a professor of political studies at the University of Otago in Dunedin, New Zealand, is best known for having documented the “Flynn effect,” the worldwide rise in IQ scores over the last century.
Mr. Dickens previewed the study during a June 19 conference on racial academic-achievement gaps held at Harvard University’s graduate school of education in Cambridge, Mass. The full study is scheduled for publication in October in the peer-reviewed journal Psychological Science.
The authors said their findings counter studies that portray the black-white IQ gap as unchanging as well as research that suggests that intelligence differences among racial groups are due to genetics. But J. Philippe Rushton, a leading proponent of that idea, argued in an interview this week that the authors of the Brookings paper had “cherry-picked” the tests they used in their study.
“Had they included other tests, the amount of narrowing they found would have been 1 or 2 IQ points at most,” said Mr. Rushton, a professor of psychology at Western Ontario University in London, Ontario, Canada.
The researchers said they chose the tests they used for a reason: They were the only ones with decades of results drawn from nationally representative samples of test-takers. The tests they used were the Wechsler Intelligence Scales for Children, the Wechsler Intelligence Scale for Adults, the Armed Forces Qualifying Test, and the Stanford-Binet Intelligence Scales, 4th and 5th editions.
Across all four types of tests, the researchers saw the same narrowing patterns. On the Wechsler tests for children, for example, the average score for black students is currently 92.1, compared with an average score of 103 for white students. The gap between the two groups was 16 to 17 points in 1978, the earliest year for which researchers have scores for that test, according to Mr. Dickens.
What’s more, they said, the gains for blacks outpaced the gains for whites at nearly all levels of cognitive ability. But the researchers could not tell from the data exactly when the black scores began to “catch up.”
The researchers also tested out some alternate explanations for the gains they found. They ruled out, for instance, the possibility that the tests had somehow gotten easier for blacks or that increasing rates of racial intermarriage had contributed to the growth in scores. The scholars also checked to see whether the data might have been skewed by the rise in the number of young black men who were imprisoned between 1980 and 1997 and thus removed from the test-taking population, and rejected that hypothesis as well.
“Therefore, environment has been responsible,” they conclude. “The last two decades have seen both positive and negative developments: gains in occupational status and school funding have been accompanied by more black preschoolers in single-family homes and lower income in those homes. We believe that further black environmental progress would engender further black IQ gains.”
If the IQ-score trend continues at the current rate, Mr. Dickens said, the racial IQ gap could close in 50 to 60 years.