September 22, 2005

How to test Evolutionary Psychology's "Domain Specific Mental Module" Theory

My teenage son has been reading philosopher Daniel Dennett's book Consciousness Explained (I've never read it -- I'm sure it's beyond me) and we were discussing Tooby and Cosmides's theory that all sorts of different mental skills evolved rather than a general factor of intelligence (although domain specificity and the g Factor are by no means mutually exclusive). I suggested that it's hard to imagine what particular selection pressure would select for the specific skill to write Consciousness Explained, and that the enormous amount of intelligence Dennett musters to attack a problem ("Why are we conscious?") of no conceivable practical importance during the supposed Era of Evolutionary Adaptation implies that we possess, in differing degrees, a fair amount of general problem solving ability (a.k.a., the g Factor).

Turning to a specific example of hypothesized domain specificity, my son mentioned the famous evo-psych experiment called the "Wason four card decision" test. You're supposed to figure out what's on the other side of a card based on logical rules. When presented as purely a test of abstract reasoning, only about 10% of test-takers figures it out. But when it's presented as a concrete way to detect cheaters, 75% figure it out. From this, Tooby and Cosmides have hypothesized that humans have evolved a "cheater detection module" that helps make social cooperation feasible by making us very good at sniffing out and ostracizing free-riders and other cheaters.

This sounds not implausible to me, but an alternative explanation is that we're just better motivated to detect cheaters than to solve abstract problems with little human relevance. Perhaps we evolved a tendency to want to figure out who's trying to slip a fast one past us. Once on a train ride to Machu Picchu, I sat with three English tourists who were on a round-the-world tour. For two hours they discussed nothing but who among their tour group owed whom a drink. This may sound stultifying, but the level of wit that they put into their complaints of how that parsimonious ponce Percy hadn't bought a round the whole time they'd been East of Suez made it quite amusing. (An anthropologist tells me that the conversations of Bushmen bands in the Kalahari Desert sound exactly the same as the English tourist's: Hey, you borrowed my bow and arrow twice and only let me use your Coke bottle once!)

So, the question is whether people figure out the Wason card test more accurately when it's framed as a cheater detection problem because they bring into play a more intelligent problem-solving module or simply because they try harder.. Think of the difference in effort expended between doing your taxes on TurboTax (a very domain specific software program that lets you do your taxes much more easily than on Excel, but is no good for anything else) versus doing them on Excel (a very g Factor software package that lets you do virtually anything with numbers, but not necessarily easily).

One way to approach this would be to have people solve the Wason problem while undergoing a PET scan, which measures metabolic activity in the brain. If people simply burn a lot more calories in their brain when you tell them they need to do it to nail cheaters, that suggests motivation is the key. But if their heads stay cool while solving the problem, that suggests they have engaged a particularly efficient mental module. (Of course, if we do have a highly effective specific tool for detecting cheaters, why not also apply it to other problems like the abstract version of the Wason? Indeed, all the amazing stuff that people have been able to figure out even though it was unimaginable until a few generations ago -- e.g., quantum mechanics -- suggests that humans are particularly good at applying mental abilities that evolved under different conditions to new problems.)

Indeed, you might not need expensive pet scans at all, but perhaps could measure calories burnt in the brain just by measuring perspiration on the forehead, which is a proxy for brain effort (brains that are thinking hard burn a lot more calories than brains that aren't). Keep the laboratory warm and see under which scenario they sweat more.

Perhaps I'm all wrong about this question of the brain generating more heat the harder it works, but I'm highly aware of it in myself. When I start thinking hard, I start sweating from the head down, and it's rather an unpleasant feeling.

In fact, I made sure to get an Intel Centrino chip in the laptop I bought 18 months ago precisely because it generates less heat than a Pentium chip and thus is less likely to overheat my office when I'm thinking hard. The Pentium is working almost all the time, putting out a lot of heat (that's why the fan runs most of the time on your Pentium PC), but the Centrino chip hibernates when it doesn't need to do something, even between keystrokes (which is why when the fan does come on, it's frequently a sign that the PC has gotten hung up in some kind of infinite loop and a "Not Running" program needs to be shut down using the Task Manager).

For example, as I blog this, I'm barely breaking a sweat because I'm not working very hard on this because, well, I'm not getting paid for it, and I expect that readers will recognize this and put up with some rambling. On the other hand, when I'm writing a movie review, I sweat a lot (literally), because I have to make it between exactly 730 and 740 words long, I have to achieve certain tasks I set for myself -- describe the movie to someone who has never seen it, evaluate its quality, and analyze some broader social, political, or artistic issue that the movie raises -- and I have to make all those disparate parts of the essay flow from one to another in a seemingly natural and effortless manner. When I'm working hardest mentally -- such as when trying to figure out what order to put the paragraphs in an essay so they flow most easily -- my PC is typically working least hard, so now that I have a Centrino PC, we complement each other. I much less often need to turn on the air conditioner just to cool down my office, which saves a lot of money.

Bruce T. Lahn recently announced the discovery of a couple of alleles of genes related to brain development, which in defective form can cause microcephaly (pathlogically small brains). These new alleles both appear to have emerged in modern humans somewhere in Eurasia after the Out-of-Africa event, and neither is as common in Africa as in Eurasia today. They are evidently favorably mutations because they spread much more quickly than random chance would allow, at least through some parts of the world.

The following is some loose speculation, which I'm sure I'll be denounced for by all the nice people, because nothing is more disreputable these days than tossing out hypotheses about human differences, especially if the nice people feel uncomfortable reading them because they remind them of things they've vaguely noticed too.

One possible cause of Lahn's new alleles would seem to be that they might have been adaptations suited for cooler climes where the amount of heat generated by the brain was less of a limitation than in tropical Africa. Perhaps one or both of these genes simply made the brain larger (there are modest average differences in brain size among the races with East Asians averaging the largest, when adjusted for body size, Europeans in the middle, and sub-Saharan Africans smaller.)

Skull shapes seem to be related in some way to this problem of shedding or conserving heat. The Eskimos, for instance, have the most spherical skulls, which minimizes the surface area per unit of volume, thus best conserving heat.

That's why you should always wear a hat in very cold weather: because your body prioritizes blood flow to the brain to keep it within its proper temperature range. If necessary, it will allow frostbite to hit your extremities in order to keep the brain at the right temperature. In general, though, I think humans have a harder time cooling their brains than warming them, which is one reason why the invention of air conditioning has done the American South so much good economically -- AC allows hard thinking to go on 12 months of the year in a place like Houston, which was almost physically impossible before it came along.

I've noticed the Kenyan Olympic distance runners, in contrast, seems to have narrow skulls giving them a lot of surface area per unit of volume, allowing them to shed heat quickly.

Or possibly Lahn's mutations just encouraged the brain to run hotter because the chance of overheating was lower in Eurasia than in Africa. By way of analogy, the most famous marathon in the country is run in Boston in April because the cool weather allows faster times than if it were run in Atlanta in August. (It's dominated by men from the cooler highlands of east Africa, by the way, while men from the warm lowlands of west Africa concentrate on the sprints instead.)

Or maybe, paradoxically, these favorable mutations make the brain run cooler. I believe, although I could be wrong, that smarter people tend to generate less heat per unit of problem-solving cognition, just as a well-greased automobile engine is less likely to overheat per unit of work done. Indeed, Edward M. Miller proposed a decade ago that well-greased brains (i.e., with higher myelination) would tend to be smarter:

The brains of the more intelligent actually used less energy than brains of the less intelligent (Haier et al. 1988, also see Haier et al, 1992, and Haier, 1993). The problem is to explain how brains that actually use less energy function better. One possibility is that they are faster and less error prone because of more myelination. Because the myelin is chemically inactive (serving roughly the same function as the insulator on a cable), it uses very little glucose. Most energy is used in the movement of ions in and out of axons. Thus, lower energy use in the more intelligent could be merely the result of more relatively inert myelin.

Knowing zip about neurology, this struck me as pretty plausible sounding, but I haven't heard much about the theory, pro or con, ever since.

All of these hypotheses could be tested in the laboratory, using PET scans or, possibly, lower tech devices.

Brain size is perhaps related to many other important differences. For example, getting the baby's skull out the birth canal is a life-or-death problem for humans. The broader the mother's pelvic saddle, the easier this tends to be. (WWII sailors referred to women as "broads" because attractive women are wider across the hips relative to waist size than are men.) But, generally speaking, the wider the hips, the slower she is as a runner.

While west and east Africans are adapted for different running lengths (short and long distances, respectively), they both tend to have efficient strides built around having narrower hip bones. (I don't think men in Africa would have made up the slang term "broad." They might have come up with "deep" to refer to how the hips of attractive African women tend to be more pronounced in the third dimension.)

This pelvic narrowness may have something to do with why African-American appear to gestate their babies about one week less on average, which is related to the major problem African-Americans have with low-birthweight babies.

I'm not saying that all this ties together, I'm just tossing out a variety of ideas, not all of which could be true, for smarter people to think about. I do think it's likely that once we get our hands on the proper thread and start pulling, we'll find out it's connected to a wide range of racial differences.

My published articles are archived at -- Steve Sailer

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