Posted by: captainfalcon | May 3, 2010

Contra Leiter

Brian Leiter has written about the third year Harvard Student who sent a post-prandial email, following up on a dinner conversation, declaring that she “absolutely do[es] not rule out the possibility that African Americans are, on average, genetically predisposed to be less intelligent.” Acknowleding that “one e-mail…is not a sound basis on which to assess someone’s intelligence and character,” he concludes, “we should absolutely not rule out the possibility that Ms. Grace is not really a right-wing racist and neanderthal.” He thus implies that the email expresses “racist and neanderthal” views.

The rest of his post, however, undermines this conclusion.

First, summarizing the current state of research into IQ and race, he writes:

[A]s I understand it, all of the following is uncontroversial:

1.  There is substantial evidence that IQ is heritable (which does not mean, contrary to what many blogs, as well as the HLS student, seem to think, that it has a genetic basis).

2.  IQ is, at best, a controversial measure of intelligence.

3.  There is no evidence–literally, none–that IQ differences between racial groups have a genetic basis.

After reading an essay by Ned Block (linked by Leiter), I now understand the difference between a trait that is heritable and a trait that has a genetic basis. Before I read that article, I would have assumed that a heritable trait just is one with a genetic basis. So, told that any trait – including IQ – is heritable, I would have assumed that meant it had a genetic basis.

Does this make me a neanderthal (and, depending on the context, a racist, as well)? If it does, then it also makes Eugene Volokh a racist and neanderthal. As Leiter observes, “Professor Volokh appears to be as confused about heritability and genetics as the Harvard student.” Nor does Ned Block – Leiter’s authority on the distinction – seem to think the conflation of something’s being heritable and its having a genetic basis evidence of racism or idiocy. Focusing on The Bell Curve, Block identifies

a principle that, though never articulated, underlies all of Herrnstein’s and Murray’s thinking on genes and IQ:

Fundamental Principle: if a characteristic is largely genetic and there is an observed difference in that characteristic between two groups, then there is very likely a genetic difference between the two groups that goes in the same direction as the observed difference.

But while the Fundamental Principle seems intuitively plausible, it is either irrelevant to the Herrnstein-Murray argument, or simply false (emphasis added).

I understand Block to be saying that the Fundamental Principle given the sense it needs in order to support Hernstein’s and Murray’s claim is intuitively plausible. Or, put another way, that it requires some care to see why the Fundamental Principle doesn’t support Hernstein’s a Murray’s claim. That is why he spends a full section explaining why it fails to do so.

Finally, that the distinction between something’s being heritable and its having a genetic basis does not come intuitively to all fair-minded people is further evidenced by Stephen Jay Gould’s tripping over it. As Block writes,

Even Stephen Jay Gould, in his otherwise excellent article in The New Yorker, missteps [in implicitly accepting that “Blacks are worse off both genetically and environmentally: some of the gap is genetic, some environmental”]. Apparently accepting The Bell Curve‘s way of conceiving the issue, he complains that Herrnstein and Murray wrongly minimize the large environmental malleability of IQ. He says that they turn “every straw on their side into an oak, while mentioning but downplaying the strong circumstantial case for substantial malleability and little average genetic difference.” Gould does not do enough to guard against the natural interpretation of “little average genetic difference” in the context of discussion of The Bell Curve as little average genetic inferiority of blacks.

Does this imply that Gould doesn’t recognize that a trait’s being heritable and its having a genetic basis are two different things? Of course not, but it does suggest that the distinction between heritability and a genetic basis is not the most intuitive of things. (If someone who deals with the distinction all the time finds himself erroneously implying that heritability entails genetic basis, that is evidence that we’re disposed to see heritability as entailing a genetic basis.)

So I think Leiter is wrong. One doesn’t have to be a racist or an idiot to think that a trait’s being heritable implies that it has a genetic basis. Couple that understandable error with the recognition (a) that “[t]here is substantial evidence that IQ is heritable” and (b) that Blacks tend to perform less well than Whites on IQ tests,  and you get to a point where you can’t “rule out the possibility that African Americans are, on average, genetically predisposed to be less intelligent.”

None of this, of course, speaks to the question whether the student ought to have made sure she wasn’t making any (even understandable) errors before she entertained the possibility she did. Maybe there is no context, including a chew-the-fat email, in which one should speculate that (inquire whether? – that too implies that you are entertaining it as a possibility) members of one race are, on average, less intelligent than members of another race for genetic reasons, without first being sure that the basis of one’s speculation isn’t confused. That, for all I’ve said, is still an open question. But it’s also a different – and more difficult – question than whether she should have made sure she wasn’t making any racist and neanderthalic errors before she entertained the possibility she did.



  1. Don’t hop on the Block-Leiter bandwagon so quickly. Heritability is very strong probabilistic evidence of genetic cause even though, as Lewontin showed, it’s not 100% conclusive proof.

  2. Uh. This is always one of the most fruitless debates around. In addition to the heritability/genetic determination issue (which I think the Lewontin hypothetical most aptly parses), intelligence is influenced by hundreds of genes through all manner of channels and most environmental effects from conception to post-puberty, in addition to every gene-gene and gene-environment interaction (little of which we actually understand), “race” as commonly understood is an absurd lens through which to understand genetics (for example: within group variability of Sub-Saharan Africans accounts for much of the genetic variance within the human race), IQ being a questionable identifier of
    “intelligence,” and the likely fact that inherited components and environmental components in neurobiology don’t quite deal with the same things (instead, its often like height, where genes indicate potential and the environment controls actualization). So even leaving aside the question of whether the student understood heritability vs. genetic determination, they would be correct in saying that we cannot “rule out the possibility that African Americans are, on average, genetically predisposed to be less intelligent.” However, using the primary context in which it would true, it would be utterly uninformative: a statement of our uncertainty on a virtually unknowable and superfluous topic, like stating we cannot rule out the potential that tiny, undetectable angels cause gravity.

  3. **for example: within group variability of Sub-Saharan Africans accounts for much of the genetic variance within the human race), IQ being a questionable identifier of
    “intelligence,” ***

    1. But genes occur in different frequencies across groups. There is a discussion here of how this can lead to group differences in phenotypes even if every version of every gene is found in two groups — as long as the frequency or probability distributions are distinct.

    2. Well, it seems to do a pretty good job of measuring problem solving skills which are valuable in modern society. Harvard Professor, Steven Pinker wrote last year in the New York Times (‘My Genome, My Self’ 11 Jan 2009):

    “To study something scientifically, you first have to measure it, and psychologists have developed tests for many mental traits. And contrary to popular opinion, the tests work pretty well: they give a similar measurement of a person every time they are administered, and they statistically predict life outcomes like school and job performance, psychiatric diagnoses and marital stability. Tests for intelligence might ask people to recite a string of digits backward, define a word like “predicament,” identify what an egg and a seed have in common or assemble four triangles into a square. Personality tests ask people to agree or disagree with statements like “Often I cross the street in order not to meet someone I know,” “I often was in trouble in school,” “Before I do something I try to consider how my friends will react to it” and “People say insulting and vulgar things about me.” People’s answers to a large set of these questions tend to vary in five major ways: openness to experience, conscientiousness, extraversion, agreeableness (as opposed to antagonism) and neuroticism. The scores can then be compared with those of relatives who vary in relatedness and family backgrounds.

    The most prominent finding of behavioral genetics has been summarized by the psychologist Eric Turkheimer: “The nature-nurture debate is over. . . . All human behavioral traits are heritable.” By this he meant that a substantial fraction of the variation among individuals within a culture can be linked to variation in their genes. Whether you measure intelligence or personality, religiosity or political orientation, television watching or cigarette smoking, the outcome is the same. Identical twins (who share all their genes) are more similar than fraternal twins (who share half their genes that vary among people). Biological siblings (who share half those genes too) are more similar than adopted siblings (who share no more genes than do strangers). And identical twins separated at birth and raised in different adoptive homes (who share their genes but not their environments) are uncannily similar.”

  4. MK:

    Thanks for taking the time to respond to my comment. Here are some quick thoughts I had on your points:

    1. I think you might have misunderstood the example. It notes not a discrepancy of gene frequencies between designated groups, but a discrepancy between the variation within groups. Further, it speaks nothing about the connection between ones genes and ones IQ but the utter arbitrariness of “race,” genetically speaking. Race splits humanity based on physical characteristics that are millions of years apart and in many cases quite shallow and creates groups that are poly- and paraphyletic. Further, as the example suggests, most of the tree of human genetic diversity gets lumped into one branch while the descendants of one minor branch of this African ape get a handful of petty physical attributes picked apart. Thus genes that code for things like epicanthic folds are assumed to be in linkage disequilibrium with (some of) those associated with intelligence because of an observed correlation. It is patently ridiculous. This is not to say that there are not genetically relevant ethic divisions one can create throughout humanity; its simply that the assumptions made hundreds of years ago about how where those divisions lie were misguided.

    2. The pragmatic utility of IQ is certainly undeniable. The weaknesses start to arise when we try to define the term “intelligence” as something other than “what an IQ test measures” and then from there, to assume that IQ tests do indeed still measure it. This remains an open question and yet another reminder of the futility of having this argument.

    3. Putting aside the fact that, despite the points made in the original post, genetic determination and heritability get conflated (presumably by yourself, as the author quoted is quick to fill things with the necessary caveats like “within a culture”), if your point with the second graf is to reinforce the notion that much of animal behavior has some genetic roots, then I doubt much of the scientific community would disagree. Indeed, almost all of ethology is now predicated on that notion. Intelligence is certainly included in this pile. There are genetic factors that influence intelligence, just as there are environmental factors, but they are both so numerous and so intertwined that trying to pick things apart and make a positive claim (in any direction) on the matter is simply unsubstantiatable. Like I said in my original comment, intelligence is likely the product of nearly every neurological gene in the genome, in addition to many that are only tangentially neurological (an obvious, layman’s example, having a Y or a second X sex chromosome has a sizable influence on hormone levels throughout development, which in turn greatly influence brain development). All of these genes all interact in complex ways (both pre- and post-transcription) with each other as well as with nearly every environmental cue a person encounters between conception and the completion of puberty (all of which likely have their own independent influences on intelligence). Further, it is also likely that all of these different elements affect different aspects of intellectual development in non-random ways (as with the analogy to height and potential vs. actualization). Thus, literally no all-encompassing statements can be made on the matter. Please, then, when tempted in the future to engage people about race and intelligence, just argue about the size of the pixies on Mars or something else that is just as unknowable and irrelevant, but much less likely to antagonize others and embarrass yourself.

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