Thursday, June 10, 2004

Heritability, Lies and Stupidity

I'm taking some time out of a packed schedule today to address some falsehoods that were being pushed by anti-immigration nuts in the comment thread accompanying my last post about immigration. In particular, since I don't have the time to address all of the very many nonsensical claims made in that thread, I'm only going to deal here with a particular brand, one centred on the issue of heritability.

Lies about Heritability - I

First off, what does it mean to say that "X has a heritability of 0.8"? One might think the meaning of this is straightforward enough, but one would almost certainly be wrong. To begin with, there is no such thing as heritability divorced from context - heritability figures can differ between populations, and can differ even for the exact same population, simply by changing the amount of environmental variation. There is absolutely nothing extraordinary about this claim, as it falls straight out of the textbook definition of heritability*, which is as follows:
h2 = VA/VP
where h2 is the coefficient of heritability usually seen being paraded by ignorant charlatans as if it were some sort of talisman, while VA represents the variance of additive genetic differences, and VP the variance of phenotypic differences.

From the equation it ought to be clear that anything that leads to a widening (shrinking) of environmental variation for a given population will decrease (increase) the heritability of a trait, even without the slightest change occurring in the genetic makeup of the population. Anybody who says something like "the heritability of IQ is 0.50" without in any way qualifying that figure to a particular population under particular circumstances is therefore a liar or an idiot, and probably both.

*Actually, the more precise phrase to use here is narrow sense heritability. That those who love to rant about heritability never bother to state just what kind of heritability they're talking about is yet another giveaway that one is dealing with ignorant cranks with just the minimum familiarity with genetics to provide them with a veneer of scientific plausibility.

Lies about Heritability - II

The second falsehood about heritability that is perpetuated by racist cranks who like to fulminate about the evils of immigration is that if a given trait has a very high heritability figure, any efforts to change it must necessarily be doomed to failure; in fact nothing of the sort is true.

To see what I'm getting at, consider the following hypothetical example: we have five families, A, B, C, D and E, amongst whom the heritability of IQ is 1.0, i.e, 100%. This heritability figure is far out of the bounds of possibility, but for that very reason it suits my argument perfectly. Anyway, let us assume that families A through E are situated in rural Farkistan, all sharing the exact same environment, and that the IQs of their members are assessed at A=65, B=70, C=75, D=80, and E=85. Let us now suppose that families A through E now immigrate to the Nordic kingdom of Blisstonia, where universal access to uniformly high-quality education and healthcare can be taken for granted; what would one expect to happen to the IQs of the next generation? If one were to buy into the idiotic reasoning of the anti-immigration shitheads, one would assume that since heritability is 1.0, the IQs of the immigrant families' children would still range from 65 to 85, when in fact it could actually transpire that the real IQ numbers are A=105, B=110, C=115, D=120, and E=125, perfectly in keeping with the complete heritability of IQ!

In plain English, heritability in itself says nothing about the degree to which a change in circumstances can lead to changes in the value of a trait, a fact which is seen easily enough when one considers that height is one physical trait with extremely high heritability under most circumstances, and yet one which is well known to respond dramatically to changes in childhood nutritional intake. It is the mark of the uninformed charlatan to sigh and point out the supposed high value of IQ heritability as evidence that Mexicans and Guatemalans are forever doomed to be hewers of wood and drawers of water because of their innate genetic limitations - it is bad enough that one is illegitimately taking heritability estimates for white, English-speaking, middle-class Americans and blithely applying them to vastly different populations, but to then claim that it implies that they're doomed to lives of stupidity is a dead giveaway that one doesn't have the slightest clue about what one is talking about.

Coda

I've chosen to touch here only on the issue of heritability because I'm pressed for time, but the truth is that all the arguments of the usual VDARE crowd are shot through with the same half-digested nonsense, usually carefully padded out with verbose bafflegab to disguise the intellectual emptiness of the argument being propagandized. It's been my experience that people who have a bug up their ass about nonwhite immigration cannot be trusted ever to tell the straight truth, even when they seem to be drawing on legitimate arguments and references; for instance, one would think, listening to these people, that the 1997 NAS study on immigration implied that immigrants were a net drain on America, when in truth the conclusion reached was the very opposite. As for the frequent claims that, say, each immigrant schoolchild costs the taxpayer $5,000 (or some other outrageous figure) a year, that is an out and out falsehood, based on the confusion (whether deliberate or otherwise) of average costs with marginal costs; just because per capita expenditure on elementary education is $5,000 a year does not mean that the marginal cost of educating an extra schoolchild, illegal immigrant or otherwise, will be $5,000 or anything close to it. After all, a school once built is a sunk cost, whether it houses 1 child or 1,000, so charging the price of adding child 901 to the 900 already in the building at average cost is a manifest absurdity - but that is just the sort of argument anti-immigration nuts routinely make.

Looking at the plethora of falsehoods and illogicalities routinely perpetuated by immigration restriction and race/IQ fanatics, one is hard-pressed to decide whether to lay the blame either on their mendacity or their stupidity. If the former, it means that those who make these arguments are no more than worthless Nazi scum; if the latter, it makes one wonder what gives them the right to cast aspersions on the intellectual abilities of others, given the severe intellectual limitations they themselves have displayed.