Progressive achievement gaps

Environmentalists are experts at reframing evidence in their favor. The finding that Blacks that look more negro are less intelligent than those that look more Caucasian becomes evidence against the genetic hypothesis (Nisbett). An only slight decrease in the Black-white gap after 50 years of radical intervention becomes evidence for the environmental hypothesis (Dickens). An average African IQ “only” 1.3 to 1.7 SD below the European mean is proof of global genetic intellectual identicality (Wicherts). And, of course, here’s Flynn, the master of environmentalist spin:

. It has also emerged that they steadily lose ground on white people with age. At just 10 months old, the average score is only one point behind; by the age of 4, it is 4.6 points behind, and by the age of 24, the gap is 16.6 points. This could be due to genes, but the steady rate after the age of 4 (about 0.6 IQ points lost every year) suggests otherwise, since genetically driven differences such as height differences between males and females tend to kick in at a certain age (Flynn, 2008. A tough call)

Flynn makes an argument by way of cumulative deficit theory. Cumulative deficit theory was first proposed in the 1960’s. Accordingly, the gap is due to accumulating early age cultural disadvantages:

It appears that, as Negro children get older, the discrepancy between their IQ scores and those of white children increases, while the discrepancy between the two groups’ scores on the language measures of this research decreases. At first grade level, the disadvantaged child’s experience seem .. [Deutch, 1967]

One problem with the cumulative deficit theory is that the gaps have not historically systematically increased with age. Were the cumulative deficit theory correct, the first grade IQ gap (of about 1SD) found by Coleman et al (1966) and Shuey (1966) should have magnified to about 1.7 SD or so by the time those kids were 24. Obviously, it didn’t; it’s evident that there was little accumulation of deficit. Instead of saying that the gaps increase with age, we could also say that in recent years the gaps have been decreased with youth. The cumulative deficit theory has no parsimonious explanation for this. Why, in prior cohorts, didn’t the gap increase with age and why does it currently?

The hereditarian hypothesis offers a parsimonious explanation for the contemporaneous progressive achievement gap. The HH proposes that the between population difference is of the same nature as the within population, between individual difference. Within populations the H^2 of IQ increases near linearly with age (Haworth, et al., 2009); cognitively, with maturity offspring grow to resemble their parents. As such, one would expect something akin to the following between population curve ceteris paribus, environmentally speaking:

Accordingly, a significant percent of the Black-White youth gap is predicted to be a function of parental provided rearing environments, that is, a result of environmental intergenerational IQ transference. While the between population IQ variance can be narrowed by outsourcing parenting (preschool, Head Start, early intervention, etc.), as the children age, it is predicted that their IQs will regress towards that of their parental population’s mean — just as children within populations do. This is, in fact, what is seen in Flynn’s IQ computations and in both adoption and early intervention studies (e.g. Perry, Abecedarian, and Chicago Early Childhood program).

Flynn’s argument that the steadily increasing difference with age makes a genetic hypothesis improbable is curious. I strain my mind to think of an environmental factor or set of them that can produce a steadily widening differences with age form early childhood to adulthood and then abruptly level off at approximately the same time that the increase in the heritability of IQ does so. Were the cause parental environment at age 4, black youth culture at age 12, and something else at age 20, one would expect a volatile change which, according to Flynn, does not exist.

It’s not that curious, because it’s clear that Flynn is playing games here. After all, at the beginning of the article, he writes that:

IN 2008, African Americans face a mainstream white culture which tells them they have “worse” genes for IQ than white Americans – and that “irresponsible” sexual behaviour dooms well over half of their children to live in single-parent homes and poverty

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One Response to Progressive achievement gaps

  1. chris says:

    I wonder if anyone is recording all the misinformation promulgated by liberal/progressive/leftist scientists about race and intelligence for when analysis of whole population’s genomes for the genes for intelligence vindicates the hereditarian hypothesis. It would be quite enjoyable to then throw it back in their faces and ridicule and shame them into oblivion.

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