Friday, April 23, 2010

Research Byte 4-23-10: Flynn effect and black/white IQ score differences

Another Flynn Effect related article, this time focused on the black/white race IQ gap.  This article will be included in the next update to the Flynn Effect on-line archive.....hopefully soon.

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(2), 213-219.

In this Editorial we correct the false claim that g loadings and inbreeding depression scores correlate with the secular gains in IQ. This claim has been used to render the logic of heritable g a “red herring” and an “absurdity” as an explanation of Black–White differences because secular gains are environmental in origin. In point of fact, while g loadings and inbreeding depression scores on the 11 subtests of the Wechsler Intelligence Scale for Children correlate significantly positively with Black–White differences (0.61 and 0.48, P < 0.001), they correlate significantly negatively (or not at all) with the secular gains (mean r = -0.33, P < 0.001; and 0.13, ns, respectively). Moreover, heritabilities calculated from twins also correlate with the g loadings (r = 0.99, P < 0.001 for the estimated true correlation), providing biological evidence for a true genetic g, as opposed to a mere statistical g. While the secular gains are on g-loaded tests (such as the Wechsler), they are negatively correlated with the most g-loaded components of those tests. Also, the tests lose their g loadedness over time with training, retesting, and familiarity. In an analysis of mathematics and reading scores from tests such as the NAEP and Coleman Report over the last 54 years, we show that there has been no narrowing of the gap in either IQ scores or in educational achievement. From 1954 to 2008, Black 17-year-olds have consistently scored at about the level of White 14-year-olds, yielding IQ equivalents of 85 for 1954, 82 for 1965, 70 for 1975, and 81 for 2008. We conclude that predictions about the Black–White IQ gap narrowing as a result of the secular rise are unsupported. The (mostly heritable) cause of the one is not the (mostly environmental) cause of the other. The Flynn Effect (the secular rise in IQ) is not a Jensen Effect (because it does not occur on g).

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