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“The Bell Curve” Again, and Then I’ll Stop

Re some readers’ defense of The Bell Curve, the worst of the worst science books, see two posts from my old Stevens blog “The Scientific Curmudgeon”: "The Bell Curve Revisited" and “The Flynn Effect and Genetic Determinism”. From the latter:

Flynn found that scores on virtually every kind of IQ test–administered not only to soldiers but also to students and others of all ages in at least 20 different countries–had risen roughly three points per decade for as long as such tests have existed. Similar increases have occurred in all of the 20 or so countries from which sufficient data were available. The gains ranged from 10 points per generation, or 30 years, in Sweden and Denmark to 20 points per generation in Israel and Belgium. The upward surge tended to be greatest for tests designed to minimize cultural or educational advantages by probing the ability to recognize abstract patterns or solve other non-verbal problems. One of the most respected tests is Raven’s Progressive Matrices, invented by the British psychologist J.C. Raven in 1942 and administered to people of widely varying ages since then. People tested in 1992 scored 27 points higher on average than people of the same age had scored in 1942.

Flynn’s data undermines some supposedly well-established claims of the intelligence-testing community. For example, many investigators believed that the elderly suffer a progressive and inevitable decline in intelligence, because when they take modern IQ tests their scores are lower than the scores of modern 20-year-olds. But if the average 70-year-old takes a test that was used 50 years ago, he or she will usually score as well as the average 20-year-old of that period did on the same test. Similarly, some experts have claimed that the academic success of Chinese-Americans, relative to their Caucasian contemporaries, is correlated with higher intelligence; after all, tests have shown that Chinese-Americans score higher on IQ tests. Flynn found that the reported IQ disparity resulted in part from the administration of old IQ tests to young Chinese-Americans.

The Flynn effect cannot be explained by genetic evolution. As Flynn once explained, “Over one or two generations, only a fanatical eugenics program could have made a significant contribution to IQ gains, and if anything mating trends have been dysgenic.” The question is, what could the non-genetic cause be? Every hypothesis put forward so far has flaws.

One theory is that children have become more adept at taking tests because such tests are increasingly common. But IQ tests have actually become less common in recent years; moreover, studies have shown that practice has little or no effect on IQ scores, particularly for the highly abstract, non-cultural tests that exhibit the strongest Flynn effect. Attempts to correlate IQ growth with time spent in the classroom have also failed; moreover, Scholastic Achievements Tests and other measures of academic accomplishment have remained flat or declined in the U.S.even as IQ scores rose.

Some pundits—notably the journalist Steven Johnson in his book Everything Bad Is Good For You–attribute the rise in IQ to childrens’ increased exposure to television, computer games and other media, the very forces that others have blamed for the “dumbing down” of modern youth. But IQ scores began rising well before the advent of television in the early 1950’s. The psychologist Arthur Jensen has proposed that the IQ gains are linked to improvements in nutrition. If that were true, the upward creep of IQ scores should have stalled or reversed in countries struck by famine during World War I and II.

The Flynn effect highlights the vital (if mysterious) role that culture plays in intelligence, at least as it is measured by IQ tests. It also suggests that, contrary to The Bell Curve, environmental interventions may close the gaps in IQ scores between different groups. [That is also the theme of an article in today’s (November 26) New York Times Magazine, “What It Will Really Take to Close the Education Gap,” by Paul Tough, although the article emphasizes how hard closing the gap may be.]

The Flynn effect, in short, shows that the genetic determinists don’t know what the hell they’re talking about.


Hiro Protagonist


You might want to check this out:

"The Black-White IQ Gap: Is It Closing? Will It Ever Go Away?"

Tuesday, November 28, 2006 10:00 AM - 12:00 PM
Location: Wohlstetter Conference Center, Twelfth Floor, AEI
1150 Seventeenth Street, N.W., Washington, D.C. 20036

"For decades, the difference in the test scores of blacks and whites on the SAT, National Assessment of Educational Progress test, Armed Forces Qualification Test, and traditional IQ tests has been a vexed issue for American educational policy. Two of the leading scholars of this controversial topic, James R. Flynn of the University of Otago (New Zealand) and Charles Murray of AEI, will debate the causes of the difference, its implications, and recent trends. New studies of the subject by Professor Flynn and by Mr. Murray will be available for distribution at the session.",filter.all,type.upcoming/event_detail.asp

If you can't make it in person, don't fret - it will be archived on the AEI website .

John Horgan

That's timely. I teach my war class on Tuesday, but thanks for the tip Hiro. Please pass along links to any materials that emerge from this event.

Roger Schlafly

You make an argument that the Flynn effect is unexplained. So what does this prove? Does The Bell Curve give some explanation of the Flynn effect that is demonstrably incorrect?

The book makes arguments about how intelligence is correlated with various other factors and outcomes. Does the Flynn effect somehow prove that those correlations do not exist? I don't get your argument that the book is bad science.


You haven't actually read "The Bell Curve", have you?

The comments to this entry are closed.

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