What IQ doesn‚Äôt tell you about race

IQ has suddenly become a hot topic again, owing to a certain DNA-discovering Nobel laureate putting his foot in his mouth and the publication of a couple of books on the subject. Malcolm Gladwell has written a great article for the New Yorker that summarises many of the recent arguments and suggests why comparing IQ scores of different races is doomed to failure.

IQ is designed so it always has a mean of 100 and a standard deviation of 15. However, during the past decades people have been scoring better on IQ tests, something known as the Flynn effect, meaning the new versions have been re-adjusted to make sure the mean stays at 100.

This is important, because it means that comparing IQ from the 1950s is not a far comparison to IQs from the 2000s, because they use tests with different standards.

Some of the people who argued that certain races are more intelligent than others have failed to include these changes in their calculations, and, as Gladwell points out, when these are accounted for, many of these differences completely disappear.

The best way to understand why I.Q.s rise, Flynn argues, is to look at one of the most widely used I.Q. tests, the so-called WISC (for Wechsler Intelligence Scale for Children)…

For instance, Flynn shows what happens when we recognize that I.Q. is not a freestanding number but a value attached to a specific time and a specific test. When an I.Q. test is created, he reminds us, it is calibrated or “normed” so that the test-takers in the fiftieth percentile—those exactly at the median—are assigned a score of 100. But since I.Q.s are always rising, the only way to keep that hundred-point benchmark is periodically to make the tests more difficult—to “renorm” them. The original WISC was normed in the late nineteen-forties. It was then renormed in the early nineteen-seventies, as the WISC-R; renormed a third time in the late eighties, as the WISC III; and renormed again a few years ago, as the WISC IV—with each version just a little harder than its predecessor. The notion that anyone “has” an I.Q. of a certain number, then, is meaningless unless you know which WISC he took, and when he took it, since there’s a substantial difference between getting a 130 on the WISC IV and getting a 130 on the much easier WISC.

Link to Malcolm Gladwell article in the New Yorker.

2 Comments

  1. Posted December 13, 2007 at 10:41 am | Permalink

    I´ve rescued this quote from the official site of the renowned sociologist Diego Gambetta:
    “There is no basis in scientific fact or in the human gene code for the notion that skin colour will be predictive of intelligence.” (Craig Venter)

  2. Kalliste
    Posted December 14, 2007 at 10:18 am | Permalink

    I’ve met Flynn, had lunch with him. He’s a good guy. But we really need to chat some more.
    Of course, to some extent people are really on average smarter than 100 years ago – they’re also taller and better fed and live longer. This doesn’t offer a complete explanation of the Flynn effect or negro-caucasian IQ differences however.
    Intelligence is highly heritable and it appears to be strongly sex-linked. The supposition is that the many genes implicated in intelligence are on the X chromosome. It’s the IQ of the mother that’s important, not that of the father. It’s also why siblings can have widely varying intelligence levels. It’s why the variability of male intelligence is greater. If you don’t understand why, go back and study some basic genetics.
    One problem that Flynn should be aware of – because I was there with him when it was being discussed – is that tests aren’t being renormed nowadays as they should. It’s an expensive process and and many people don’t like the inferences being drawn from IQ testing and like to sideline it, and its funding. So although norming of tests is an issue in comparing across generations Flynn’s account of it is, shall we say, debatable.
    Flynn’s insights are very valuable and he’s pointed up a real issue to be debated. Many people working in the field do believe that people have simply become better at IQ type tests because of the way the educational system has developed. However – the enduring differences between negro and caucasian scores are a lot harder to explain than your’s, and Flynn’s, account suggest.
    Venter’s comment isn’t even worthy of quoting. Skin colour doesn’t even have anything much to do with race – many Caucasians have very dark skins, e.g. southern Indians. Nobody, AFAIK, has ever maintained genes involved in skin colouration have anything to do with intelligence. That’s not to say they don’t but it seems unlikely at present.
    Flynn is a genuine guy who is looking at the data and doing some real science. Sadly many in the field are not, they have axes to grind one way or another. But jumping on Flynn’s thesis and embracing it uncritically and wholeheartedly just because it matches your particular prejudices is equally as invalid as embracing the notion of a `black-white IQ difference’ because it suits your racist bent.


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