Racial Differences in IQ Only Manifest at Age 2

Once again, the IQ race wars have flared up again (here, here, here, here, and here).

I’ve never been a big fan of IQ except to identify people who are very smart or very dim–which were the original purposes of these tests (actually, they were primarily used to determine who was too stupid to carry a rifle, or so smart, they should spend their time trying to build a better rifle). When you factor in the Flynn effect, I think we’re reading far too much into these scores, a point DrX makes:

The focus in the political discussion has been on Full Scale IQ score, that single number that fascinates many lay people. FSIQ is of relatively limited clinical utility. There are circumstances in which that number is diagnostically relevant to a referral question and to our recommendations, but in my experience, it is not particularly relevant for most cases. Yes, you can say that someone with an IQ of 85 isn’t going to be up to college level work, or that someone with an IQ of 130 has a great deal of intellectual capacity, but more often we’re interested in specific cognitive functions, and we’re looking for patterns of relative strengths and weakness across numerous functions to develop our diagnostic hypotheses.

As DrX notes, it’s the components of cognition that might–emphasis mightreveal something interesting.

In addition, when we look at something like educational achievement (the NAEP), we see that black children today score higher than white children did twenty years ago, and the gap between white and black has narrowed. If you believe that IQ would be correlated (albeit imperfectly) with educational performance, we either must conclude that IQ is very malleable or that it simply doesn’t matter except at the extremes.

So this paper (pdf) I found by way of Jason Johnson is very interesting–here’s the abstract (boldface mine):

On tests of intelligence, Blacks systematically score worse than Whites. Some have argued that genetic differences across races account for the gap. Using a newly available nationally representative data set that includes a test of mental function for children aged eight to twelve months, we find only minor racial differences in test outcomes (0.06 standard deviation units in the raw data) between Blacks and Whites that disappear with the inclusion of a limited set of controls. Relative to Whites, children of all other races lose ground by age two. We confirm similar patterns in another large, but not nationally representative data set. A calibration exercise demonstrates that the observed patterns are broadly consistent with large racial differences in environmental factors that grow in importance as children age. Our findings are not consistent with the simplest models of large genetic differences across races in intelligence, although we cannot rule out the possibility that intelligence has multiple dimensions and racial differences are present only in those dimensions that emerge later in life.

The statistics seem sound to me. One of the things about IQ is how malleable it appears to be. Without rigorously specifying the environment, finding a genetic basis for IQ will be damn hard (if it exists in any appreciable sense at all). Something this malleable will definitely be screwed up by genotype-environment covariance.

Oddly enough, this paper didn’t receive much media (or blogger) coverage….

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2 Responses to Racial Differences in IQ Only Manifest at Age 2

  1. Nomen Nescio says:

    trying to measure something we can’t even clearly define, and measure it as a single scalar quantity at that, is silly. a very human thing to do, exactly the sort of hasty overgeneralization people like to indulge in, but still silly.

    i’d pay more attention to IQ measures and the debate wars around them if the damn numbers actually translated into something tangibly useful, but they don’t really seem to. as one piece of worthless anecdata, myself; i’m about two sigmas north of the average, yet that has not provided me with any particular success in life. by analogy, being two sigmas short of it probably doesn’t damn a person to misery, either.

  2. Min says:

    On the malleability of IQ scores: There was a classic experiment in the 50s or 60s in which teachers were given false IQ scores for some elementary school children at the beginning of the school year. Students whose scores had been falsified upwards showed greater increases in their IQ scores at the end of the year than students whose scores had not been falsified. :)

    On race and IQ: It has been shown that the language of the test matters. (Big Duh!) You know those test questions of the form, “A is to B as C is to _”? Back in the 50s it was known that inner city Black kids scored worse on them than average. However, research showed that if you change the language to “A goes with B like C goes with _ ” the difference in scores disappeared. Despite that fact, the ETS did not change the language of those questions.

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