Attention Conservation Notice: 1500-odd words on the plasticity and importance, or lack thereof, of certain human faculties, a topic of endless controversy; a controversy which, like the air from a blow-drier, is both arid and heated, and which this certainly won't settle. Written in dialog form, which is always pretentious, especially when not used to good effect, which it isn't here.
Q: Very good. (It didn't fit the rhythm, and anyway they get the picture.) How would you react to the idea that a psychological trait, one intimately linked to the higher mental functions, is highly heritable?
A: With suspicion and unease, naturally.
Q: It's strongly correlated with educational achievement, class and race.
A: Worse and worse.
Q: Basically nothing that happens after early adolescence makes an impact on it; before that it's also correlated with diet.
A: Do you work at the Heritage Foundation? Such things cannot be.
Q: What if I told you the trait was accent?
A: I'm sorry?
Q (in a transparently fake California accent): When you, like, say words differently than other people? who speak, like, the same language? because that's how you, you know, learned to say them from people around you?
A: Do you have a point to make, or are you just yanking my chain?
Q: Would you agree that accent has all the characteristics I just described?
A: Higher cognitive functions — heritable — class and race — not plastic after adolesence — correlation with diet, hah! — I guess I must.
Q: But would you say that there is any genetic or even congenital component to accent?
A: Not really. Obviously, some congenital conditions, like deafness or defects of the vocal chords, make it hard to impossible to acquire any accent. And I can imagine, though I don't know of anything, that there might be very specific mutations which make it hard to hear a distinction between a given pair of sounds, or easier to learn a specific distinction. But, in general, no, there is no non-trivial genetic component to accent.
Q: Then why were you worried that I was about to start channeling Arthur Jensen?
A: Because those are the sorts of claims usually trotted out by people who want to claim that something is innate, un-plastic, and usually invidiously distributed; sometimes there is a "sadly" to the claims of group inferiority, and sometimes, I think, that "sadly" is even genuine.
Q: That last sentiment is overly magnanimous. But rather than argue about that, turning this into a genuine dialog, I will continue to ask leading questions. — Surely the example of accent shows the weakness of that line of argument?
A: Indeed. Accent, which transparently is not innate and is plastic, has all these features; therefore those features do not, reliably, point to innateness, or point away from plasticity. Therefore, even if IQ scores have these features, it does not, by that token, mean that they reflect some kind of unalterable trait of the organism.
Q: Would you care to push the analogy further?
A: By all means.
Q: In the wild, so to speak, accent is highly heritable across the general population, and (at least in the US), strongly correlated with race. Does this imply that there is a genetic basis to racial differences in accent?
A: Manifestly not.
Q: Can accent change significantly over the space of a generation or two, within a single population, without being driven by outside forces?
A: The work of William Labov &c., if nothing else, would seem to have established this, yes.
Q: How would you explain this sort of change?
A: Accent is the result of learning from adult speakers and from other children; while I don't think we know too much about the precise mechanisms of accent, we do know that many sorts of social learning, including ones relevant to language, are prone to herding and large swings of collective behavior.
Q: So you would say that this sort of rapid change within a given population is suggestive of a trait which evolves culturally, rather than genetically?
A: That question is very ill-posed. If anything, it reminds me of one of my perpetual frustrations with much of psychology and sociology, which is the way that they have taken some early statistical tools, more bits of descriptive statistics and error analysis than anything else, and fetishized them as the Platonic forms of mathematical theory and causal analysis.
Q: Do you think that you can rant against such idolatry of linear regression and analysis of variance better than Clark Glymour can?
A: No, so I'll leave that to him. (Do follow that link, though.) To return to your question, there must be a genetic basis to having any accent at all. I would guess that there is a range of accents which are all easy to acquire, surrounded by a penumbra of accents which ordinary human beings would find hard to acquire, and then beyond that accents which while they might be logically conceivable are just not learnable. The location of these sets could change with genetic changes. But, holding the gene pool more or less fixed, moving around with the space of easy-to-learn accents seems to be entirely due to social learning processes.
Q: So, taking all those disclaimers into consideration, what does the analogy to accent suggest for the Flynn Effect?
A: The which?
Q: I'm supposed to be asking the questions, I'm "Q" and you're "A"!
A: Look, I'd be perfectly happy to answer if I had some idea of what I am answering a question about! Even in a weblog, is that too much to ask?
Q: Very well, just this once: the Flynn Effect is a phenomenon first noticed by James Flynn, looking at data on intelligence tests which were not re-normed over time. If you have the same people take two different years' versions of the tests, you can see how well the median test-taker in year X would have done on the year Y test. The conclusion is that if we had kept using the same IQ tests over the course of the twentieth century, the average IQ would have risen something like two to three points every decade — sometimes less, sometimes even more, but always somewhere in that vicinity. This even applies in situations where you can pretty much rule out differential reproduction or immigration (e.g., test scores of Dutch army recruits).
A: So an IQ of 100 in 1900 would be equivalent to an IQ of 80 or even 70 today?
Q: Yes; which is borderline mental retardation.
A: Well, one possibility is that many people did use to be really stupid; the generations of 1900 and 1910 were the ones who brought us the Great War, after all. Anti-democrats like Pareto or Nietzsche may in fact have accurately gauged the mental abilities of their contemporaries.
Q: Didn't I ask you to put on your right-thinking left-liberal hat?
A: Oh yes, I forgot myself. Well, even if that was true, no doubt it was due to the oppression endured by the vast majority of even the richest societies, a mental counterpart to the way the aristocracy could literally look down on the lower orders.
Q: A little less of the "left" and a little more of the "liberal", perhaps?
A: Another possibility is that this doesn't reflect any sort of change in basic mental ability (whatever that might be) at all. Doing well on standardized, multiple-choice tests calls for certain sorts of cognitive skills, certain kinds of abstract problem solving. Maybe more exactly, you need both aptitude at understanding explicit rules for manipulating symbols, communicated to you through the medium of writing, with very little contextual information to help you make sense of the message, and you need to be willing to follow those rules, even when they are pointless. These are skills that come from making your way through an industrial, or more precisely bureaucratic and mass-literate, society. (Shades of Luria!) These are skills you are more apt to learn if you grow up in a household which is already highly literate, etc., than if your parents and neighbors are all displaced peasants or harrassed proles. It's certainly not surprising if someone who grows up in a household of intellectuals (that is, clerks) finds these habits easy to learn.
Q: So the analogy suggests that IQ scores are...?
A: A proxy for the skills and habits encouraged by a bureaucratic society; skills and habits which can be at once highly heritable (because of strong transmission through family and neighbors) and highly learned (within the scope of what it is biologically possible for humans to learn and internalize). Innate ability needn't enter into it at all. The implications for democracy would be nearly nil.
Q: And the famous g?
A: Is a statistical artifact, or better yet a myth; but that is another story for another time.
Update, 24 June: See the next post for more.
Update, 13 July: I am not worthy of the honor of having this post become the basis of a comment thread on Unfogged; if there is any cloud in the sky of my happiness, it is that the thread contains too few sexual innuendos.
Update, 27 September: For the boring, detailed, 11,000 word rendition of the same points, with more algebra, see here.
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Posted by crshalizi at June 22, 2007 00:25 | permanent link