intelligence

In last week's Science, Stanislas Dehaene and colleagues describe the relation of cultural invention to "universal intuition" about mathematical logic:

The mapping of numbers onto space is fundamental to measurement and to mathematics. Is this mapping a cultural invention or a universal intuition shared by all humans regardless of culture and education? We probed number-space mappings in the Mundurucu, an Amazonian indigene group with a reduced numerical lexicon and little or no formal education. At all ages, the Mundurucu mapped symbolic and nonsymbolic numbers onto a logarithmic scale, whereas Western adults used linear mapping with small or symbolic numbers and logarithmic mapping when numbers were presented nonsymbolically under conditions that discouraged counting. This indicates that the mapping of numbers onto space is a universal intuition and that this initial intuition of number is logarithmic. The concept of a linear number line appears to be a cultural invention that fails to develop in the absence of formal education (Dehaene et al. 2008:1217).

The idea is that children in Western societies have to learn that a number line is a linear representation; they begin by compressing the space devoted to large numbers:

When asked to point toward the correct location for a spoken number word onto a line segment labeled with 0 at left and 100 at right, even kindergarteners understand the task and behave nonrandomly, systematically placing smaller numbers at left and larger numbers at right. They do not distribute the numbers evenly, however, and instead devote more space to small numbers, imposing a compressed logarithmic mapping. For instance, they might place number 10 near the middle of the 0-to-100 segment. This compressive response fits nicely with animal and infant studies that demonstrate that numerical perception obeys Weber's law, a ubiquitous psychophysical law whereby increasingly larger quantities are represented with proportionally greater imprecision, compatible with a logarithmic internal representation with fixed noise (7, 20, 21). A shift from logarithmic to linear mapping occurs later in development, between first and fourth grade, depending on experience and the range of numbers tested (17-19).

They note that there's a problem testing these ideas in Western children, who are surrounded throughout their development by numbers -- in books, "elevators" and other places. Most of these numbers are small ones -- especially one through ten -- so they might naturally accentuate the ones they know.

They found when testing the Mundurucu that both adults and children tended to compress the high end of the number scale, even testing numbers between one and ten. This compression is logarithmic -- they accentuate contrasts between small numbers disproportionately. It makes sense logically -- we care more about detailed contrasts between small numbers than large numbers. They don't give an idea of which logarithm people are using; and in fact it may be different ones for different people. The important fact is the small number/large number contrast.

Dehaene and colleagues attribute this scaling to mapping at the neural level:

What are the sources of this universal logarithmic mapping? Research on the brain mechanisms of numerosity perception have revealed a compressed numerosity code, whereby individual neurons in the parietal and prefrontal cortex exhibit a Gaussian tuning curve on a logarithmic axis of number (27). As first noted by Gustav Fechner, such a constant imprecision on a logarithmic scale can explain Weber's law -- the fact that larger numbers require a proportional larger difference in order to remain equally discriminable. Indeed, a recent model suggests that the tuning properties of number neurons can account for many details of elementary mental arithmetic in humans and animals (21). In the final analysis, the logarithmic code may have been selected during evolution for its compactness: Like an engineer's slide rule, a log scale provides a compact neural representation of several orders of magnitude with fixed relative precision.

From that perspective, the Western conception of the number line appears as a very distinctive invention, capable of adjusting the logarithmic encoding to arrive at faster and more accurate mathematical conclusions about large numbers. The authors speculate that addition and subtraction (which display invariance between large and small numbers) and experience with measurement underlay the development of the linear concept in Western children.

References:

Dehaene S, Izard V, Spelke E, Pica P. 2008. Log or linear? Distinct intuitions of the number scale in Western and Amazonian indigene cultures. Science 320:1217-1220. doi:10.1126/science.1156540

On the topic of how to measure intelligence in different species, I found this passage on pp. 256-257 of Georg Streidter's textbook:

Over the last 50 years or so, it has become apparent that some nonmammals perform just as well as mammals in various learning and "intelligence" tests, as long as the tests are designed with the animal's "special needs" in mind. Davidson (1966), for example, showed that alligators fail to learn a simple discrimination task if the reward is food, but readily master the same task, in the same apparatus, if they are offered the opportunity to escape from excessive heat. Such a finding might have surprised Tinklepaugh or Edinger, but it makes perfect sense once you realize that alligators (as ectothermic creatures with low metabolic rates) can go without food for long periods of time but must frequently move out of the sun to prevent heatstroke. In other words, comparative psychologists have realized that it is blatantly unfair to run reptiles or other nonmammals through intelligence tests that were designed by mammals for mammals (Streidter 2005:256-257).

This is near the beginning of a chapter on mammalian brain evolution, the introduction of which ends: "After all, the subject of the book is the evolution of brains, not intelligence" (258). The focus on the functional and the adaptive is refreshing -- since the evolutionary utility of the brain is for solving adaptive problems.

Nevertheless, he later links expanding brain size on the mammal lineage with metabolic rate -- which may be the most straightforward of possible connections, since the sensory evolution of early mammals involved both complex gains (e.g., olfactory) and losses (e.g. chromatic vision) of function.

I'll probably be quoting more as I get into this.

References:

Davidson RS. 1966. Operate stimulus control applied to maze behavior: heat escape conditioning and discrimination reversal in Alligator mississippiensis. J Exp Anal Behav 9:671-676.

Streidter GF. 2005. Principles of Brain Evolution. Sinauer, Sunderland MA.

That seems to be the import of this story in the Times Online:

After studying 25,000 children across both state and private schools Philip Adey, a professor of education at King's College London confidently declares: "The intelligence of 11-year-olds has fallen by three yearsÕ worth in the past two decades."

On the other hand, the description of the test looks like it covers a fairly concrete set of knowledge:

In the easiest question, children are asked to watch as water is poured up to the brim of a tall, thin container. From there the water is tipped into a small fat glass. The tall vessel is refilled. Do both beakers now hold the same amount of water? "It's frightening how many children now get this simple question wrong," says scientist Denise Ginsburg, [Michael] Shayer's wife and another of the research team.

Another question involves two blocks of a similar size -- one of brass, the other of plasticine. Which would displace the most water when dropped into a beaker? children are asked. Two years ago fewer than a fifth came up with the right answer.

In 1976 a third of boys and a quarter of girls scored highly in the tests overall; by 2004, the figures had plummeted to just 6% of boys and 5% of girls. These children were on average two to three years behind those who were tested in the mid-1990s.

I'd like to think that sixth-graders could get those things right, too. But the story of the researchers -- that kid's aren't playing with sandboxes and mudpies enough anymore -- doesn't inspire me with confidence. I can definitely see how videogames might not be good training for questions about Archimedes' principle, but going from a third to a fifteenth able to "score highly" isn't necessarily about "general intelligence". I wonder if it's about less advanced coursework for talented students (i.e., the third that used to "score highly").

It does give a hint about the Flynn effect: If education can make kids do worse, it might easily have made them do better. But the outcome is unclear -- the real reason to pay attention to the Flynn effect is the increase in adult IQ. Here, it's not clear what the result for the 11-year-olds will be.

CNET is running a series of articles on the kind of intelligence required for the world of changing technology. The first installment starts thusly:

Today, terabytes of easily accessed data, always-on Internet connectivity, and lightning-fast search engines are profoundly changing the way people gather information. But the age-old question remains: Is technology making us smarter? Or are we lazily reliant on computers, and, well, dumber than we used to be?

The article's answer is that different skills don't mean different reasoning and learning. Not unexpected, since business' focus in the wake of technological change is always training and retraining the same minds for different skillsets.

The main idea is how memory is less necessary when you have devices to keep track of things for you. I suppose if Sherlock Holmes' theory of mind is right, that means we should be able to fill up our minds with deeper thoughts:

"It's true we don't remember anything anymore, but we don't need to," said [Jeff] Hawkins, the co-founder of Palm Computing and author of a book called "On Intelligence."

"We might one day sit around and reminisce about having to remember phone numbers, but it's not a bad thing. It frees us up to think about other things. The brain has a limited capacity, if you give it high-level tools, it will work on high-level problems," he said.

Of course, this presupposes that the brain isn't full of cognitive adaptations that now lie fallow and useless in today's high-tech world. Or get filled with videogames and movies. I guess these fall under the Everything Bad Is Good for You theory.

I wonder what you would call a specialized cognitive adaptation that could be readily reprogrammed in different cultures for different purposes?

As the new semester gets underway, it's a good time to think of ways to improve all those assignments I will soon be reading. Few are as pain-free as listening to some old-school music. As in classical music.

As most people know, listening to Mozart will make you smarter. At least, that was the theme of the book The Mozart Effect, loosely based (very loosely) on work in the early 1990's that found that people did better on a spatial IQ test after listening to Mozart, as compared to listening to a relaxation tape.

Dave Munger at Cognitive Daily has been reviewing how the Mozart Effect has fared in the recent psychology literature (via Keats' Telescope). This post reviews a 2002 study that challenges the idea. That paper, McKelvie and Low (2002), shows no effect at all from listing to Mozart:

So in their task, McKelvie and Low used repetitive dance music by the group Aqua to compare to Mozart.

Students were divided into two groups -- one which listened to Aqua first, and the other which listened to Mozart first. After listening to an 8-minute musical excerpt, students were tested on spatial ability. Then they listened to the other excerpt and took a different version of the same test. The result: no significant difference for any of the music. All the test scores were statistically the same. There wasn't even a trend for Mozart.

This about sums it up:

If contrasting music doesn't result in lower IQ scores, then we're really not talking about Mozart enhancing spatial IQ scores, we're talking about verbal relaxation tapes inhibiting them.

Of course, that may explain Deepak Chopra as well...

But one later paper, reviewed in this later post, tends to support some kind of positive effect of classical music on performance, although pointedly not limited to Mozart.

Ivanov and Geake offer some interesting guesses as to why the music improves performance. They point to Rausher's argument that cognitive processing levels remain essentially the same while listening to Mozart's music. They also suspect that music may help to mask the otherwise distracting background noise that is present in nearly all "silent" classrooms.

Munger also reviews a second paper with equivocal results: it doesn't support a Mozart-specific increase, but it may be consistent with a music-related increase in performance.

As for myself, I wonder if this is related to the "mariachi effect" -- you know, how they play fast music in restaurants to make you eat faster.

References:

McKelvie P, Low J. 2002. Listening to Mozart does not improve children's spatial ability: Final curtains for the Mozart effect. Br J Devel Psych 20: 241-258.

A paper by Danielle Posthuma and colleagues (2005) reports on a map survey of the human genome looking for loci that may be linked to IQ. They find two significant linkages, on chromosomes 2 and 6. The data are from a large sibling and twin study, so the question is which genomic regions are shared by siblings who are similar in IQ, but different between siblings who are different in IQ.

The report is about marker linkages, not genes, so it is not clear what genes may cause the linkages they observe. The surprising thing to me is just how many possibilities there are:

Several positional candidate genes within the 2q24.1-2q31.1 linkage region have been tested for an association to autism, including GAD1 (MIM 605363), HOXD1 (MIM 142987), DLX1 (MIM 600029), DLX2 (MIM 126255), TBR-1 (MIM 604616), RAPGEF4 (MIM 606058), CHN1 (MIM 118423), SLC25A12 (MIM 603667), SCN1A (MIM 182389), SCN2A (MIM 182390), and SCN3A (MIM 182391) (Bacchelli et al. 2003; Weiss et al. 2003; Rabionet et al. 2004; Ramoz et al. 2004). Most promising as a site with possible relevance to IQ is the significant association between the relative risk to autism and two common SNPs in the mitochondrial aspartate/glutamate carrier SLC25A12 gene (Ramoz et al. 2004).

The linkage region on chromosome 6 (6p25.3-6p22.3 [D2S942D2S422]) overlaps marginally with the region 6p22.3-6p21.3 implicated in reading disability and dyslexia (Cardon et al. 1994; Fisher et al. 1999b; Gayán et al. 1999; Grigorenko et al. 2000; Kaplan et al. 2002; Willcutt et al. 2002; Deffenbacher et al. 2004). Although recently at least five candidate genes were identified that are likely to contribute to linkage with reading disability, those genes lie just outside the region defined by a drop of 1 LOD score on 6p for VIQ and FSIQ scores (Deffenbacher et al. 2004). The ALDH5A1 gene (6p22-6p23), implicated in both cognitive ability (Plomin et al. 2004) and reading disability (Deffenbacher et al. 2004), lies at the border of our 6p region.

Several genes within the 2q and 6p linkage regions have been associated with schizophrenia (NR4A2 [MIM 601828] at 2q24, DTNBP1 [MIM 607145] at 6p22, KIF13A [MIM 605433] at 6p22, and NQO2 [MIM 160998] at 6p25), fragile X syndrome (RANBP9 [MIM 603854] at 6p23), and Bardet-Biedl syndrome (BBS5 [MIM 603650] at 2q31). These disorders are accompanied by rather severe cognitive impairment, but milder variants in these same genes could influence variation in the normal range of cognitive abilities. Recently, evidence was found for linkage at 6p24 to a neurocognitive-deficit subtype of schizophrenia, in which the maximum LOD score occurred at marker D6S309, which is within the region that shows linkage to VIQ and FSIQ (Hallmayer et al., in press). Currently, dysbindin-1 (DTNBP1) at 6p22.3 is the best-supported susceptibility gene for schizophrenia (Talbot et al. 2004). Recent identification of a relationship between dysbindin-1 and hippocampal glutamate neurotransmission, a core concept of leading neurobiological theories of memory and learning, suggests further potential as an IQ gene (Talbot et al. 2004). A second positional candidate gene thought to be involved in memory processes is NRN1 (MIM 607409) at 6p25.1, which plays a role in neuritogenesis in mature brains. Naeve et al. (1997) showed that expression of neuritin, the product of NRN1, is induced by neural activity and by the activity-regulated brain-derived neurotrophic factor and neurotrophin-3. Neuritin is expressed in hippocampal and cortical neurons and is suspected to regulate neuronal plasticity during development and in the adult brain.

Given the gradual increase in heritability of IQ from childhood to late adolescence, those genes in our regions that influence brain development may be promising as candidate genes for IQ. For example, TBR-1 (MIM 604616), a neuron-specific T-box transcription factor, plays a critical role in brain development and is specifically expressed in the cortex. It is thought to be a common genetic determinant for the differentiation of early-born glutamatergic neocortical neurons and may provide insights into the functions of these neurons as regulators of cortical development (Hevner et al. 2001, 2002). More specifically, Hevner et al. (2002) showed, using Tbr1 mutant mice, that Tbr1 is critical in the appropriate establishment of precise reciprocal projections between cortical areas and corresponding thalamic nuclei (Posthuma et al. 2005: 323, citations in original).

That's 22 different functional genes that might conceivably be related to cognition. Now, the implication of each of these genes is based only on the fact that somebody has found them to be worth studying in relation to cognition. But wow, that's a lot of potential on just two small segments of two chromosomes.

The question in this study is about what explains current IQ variation. I'm more interested in what may have changed in the past, which includes many things that may not be variable today.

References:

Posthuma D. et al. 2005. A genomewide scan for intelligence identifies quantitative trait loci on 2q and 6p. Am J Hum Genet 77:318-326. Full text online

An article of that title by Robert Lee Hotz of the LA Times is on the Yahoo News site. It is a profile of neuroscientist Sandra Witelson (McMaster University), including her research on gender differences in the brain, and her exploration of Einstein's brain tissue.

Here is an excerpt:

The brains in Witelson's freezer are contested terrain in a controversy over gender equality and mental performance.

Her findings -- published in Science, the New England Journal of Medicine, the Lancet and other peer-reviewed journals -- buttress the proposition that basic mental differences between men and women stem in part from physical differences in the brain.

Witelson is convinced that gender shapes the anatomy of male and female brains in separate but equal ways beginning at birth.

On average, she said, the brains of women and men are neither better nor worse, but they are measurably different.

Men's brains, for instance, are typically bigger -- but on the whole, no smarter.

"What is astonishing to me," Witelson said, "is that it is so obvious that there are sex differences in the brain and these are likely to be translated into some cognitive differences, because the brain helps us think and feel and move and act.

"Yet there is a large segment of the population that wants to pretend this is not true."

How did her discoveries start?

"I had the first two patients, and they were so very different," Witelson said. "I kept looking and looking at them, trying to see what the difference could be."

Then she consulted the donor documentation for each tissue sample. "Finally, I saw that one was a man, and one was a woman."

Among women, the neurons in the cortex were closer together. There were as many as 12% more neurons in the female brain.

That might explain how women could demonstrate the same levels of intelligence as men despite the difference in brain size.

"So among female brains, the cortex is constructed differently, with neurons packed more closely together," she said.

The story of Einstein's brain is too quirky to miss. Read the whole thing.

James R. Flynn is a social scientist at the University of Otago, New Zealand. Beginning in 1981, Flynn performed a series of statistical analyses on the results of IQ tests in Western populations. The analyses showed that IQ scores in every population measured are systematically rising over time, with each succeeding generation apparently smarter than its predecessor. These IQ gains have been dubbed the "Flynn effect," and the causes and patterns underlying these changes are still obscure. Flynn recounts the story of his findings in his article "Searching for justice: the discovery of IQ gains over time," in the January 1999 issue of American Psychologist, as well as discussing the current state of research into IQ changes and the moral and sociological corollaries of the research.

The initial finding of rising IQ came from looking at the pattern of correlations between successive versions of IQ tests. When publishers came up with revised versions of tests, they would apply both the new and old test to a set of the same subjects. If the subjects scored similarly on both versions of the test, it would demonstrate that the new test was measuring the same skills as the old test. But Flynn noticed something else about these results: the subjects who took both versions of the test would average a significantly higher score on the older version. Since the older version's scores were standardized at the time it was written, Flynn noted that "the only possible explanation was that representative samples of White Americans were setting higher standards of test performance over time" (5). In this first analysis, the IQ gain from 1947 to 1972 was 8 points. In a broader sample of tests, "the rate of gain was about 0.30 IQ points per year, roughly uniform over time and similar for all ages" (6, citing Flynn 1984).

In light of these results, Flynn gathered data on IQ surveys in as many nations as had routine military induction testing or other large-scale testing organizations (6). The startling result was that IQ has been increasing in every one of these countries, and that the increases were especially noted in tests that were thought to be less susceptible to biases from educational or cultural factors. The longest-term sample was available from Britain, where it became clear that the fifth percentile among persons born in 1967 was equivalent to the ninetieth percentile of those born in 1877 (Raven et al. 1998).

What should we make of this phenomenon? According to Flynn (7):

This deals a stunning blow to our confidence in the ability of IQ tests to compare groups for intelligence, at least when those groups are separated by cultural distance. Can anyone take seriously the notion that the generation born in 1937 was that much more intelligent than the generation born in 1907, to say nothing of the generation born in 1877? It also deals a blow to the Spearman-Jensen theory of intelligence. That theory is based in g, the general intelligence factor derived from the tendency of the same people to excel on a wide range of IQ tests.

Flynn relies on common sense to justify this intuition, but to the extent that the results would seem to indicate very surprising conclusions, his common sense appears to be sound. As he notes, it seems unlikely that high proportions of earlier generations would have lacked the intelligence to understand the rules of popular sports. And as he notes (7), "[achievement gains] fall away the closer we come to the content of school-taught subjects" such as "arithmetic, information, and vocabulary."

He also gives a quick rundown of the reasons suggested to explain the IQ rise over time, along with reasons why they cannot explain the entire problem. His passage on the effect of better nutrition is well worth reading. Each section is a reminder of the nature of the problem: first, can these reasons explain IQ gains that were progressive, gradual, and constant, and second, are we really to believe that earlier generations actually had intelligence as low as their scores compared to today's scores would indicate?

The social justice element of the article comes from the consideration of how apparent IQ gains affect the interpretation of race differences in IQ test performance. One section is spent considering the ways that group achievement in real terms may not represent the expectations from their IQ scores compared to other groups. Flynn focuses on the cultural and educational differences among groups as a way to explain differences in outcome that are not predicted by IQ scores.

In a second section, Flynn lays out the issues surrounding the interpretation of race differences in IQ as applied to American Blacks and Whites (his terminology). In this, he gives a thoughtful presentation of the Jensen position. This contains a very clear presentation of the concept of regression that is worth quoting (13):

The key to what follows is the concept of correlations as measures of regression toward the mean. To provide a simple example: Imagine that the correlation between height and between-family environment was perfect, or 1.00. The significance of that would be this: If we found a group one standard deviation below the mean for height, and environmental factors were solely responsible for their height deficit, then they should be one standard deviation below average in terms of environment. Now imagine the correlation is less than perfect, perhaps only .35. In that case, it would take several standard deviations of environmental deprivation to account for a one standard deviation height deficit. A bit of arithmetic shows it would take 2.86 standard deviations, because 2.86 times .35 equals one standard deviation. In summary, the correlation determines precisely how many standard deviations of environmental deficit it takes to account for a one standard deviation height deficit, or to be technical, it determines how far toward the mean the below-average group will regress as each standard deviation of environmental deficit is eliminated: clearly only 35% of the way.

As Flynn notes, Jensen's (e.g. 1972) case for Black-White IQ differences rested on the observation that between-family environmental differences had a correlation of .35 with IQ within Whites. According the the example above, it would require a deficit of 2.86 standard deviations of environmental conditions in Blacks compared to Whites in order to explain the IQ difference. According to a normal distribution, this would imply that "the average environment of Black Americans would have to be inferior to that enjoyed by 99.79% of White Americans" (13). Jensen argues that such a difference is unlikely, but in particular examines the idea that such an environmental difference might exist by discussing what its likely effects would be. In his view, a factor like racism might account for IQ differences by affecting self-image, confidence, and other social factors. But as Flynn summarizes his argument, "Who could argue that these same factors do not vary significantly within the Black population? ... If these factors both are potent and vary among Blacks, why do they explain so little IQ variance within the Black population?"

Flynn discusses Lewontin (1976) in particular as someone who argued for an environmental explanation by means of a thought experiment. Certainly there is no theoretical difficulty in imagining a nongenetic difference that would cause differences between groups without causing significant within-group differences. But one must imagine that the environmental difference was uniform within each group, which is arguably not true of any real-life human environmental variable. In Flynn's view, Lewontin's example merely begs the question of the real differences between races, since Lewontin provided no real-world example that would credibly avoid Jensen's objections.

Flynn describes his own attempts to address this issue. The major piece of evidence he drew upon (Flynn 1980) involved the IQ scores of children of the American occupation of Germany after World War II. Both Black and White American soldiers fathered children with German women, and the IQ scores of both groups of children were almost identical. Flynn argued that direct evidence of this kind, reflecting what actually occurs when different races are subject to qualitatively similar environments, is more important than the kind of indirect evidence that comes from attempting to correct samples for socioeconomic status or other environmental variables.

In addition to this kind of direct evidence, Flynn argues here that the observation of IQ test gains over time further reduces the relevance of the indirect evidence of environmental differences. For one, the gain of IQ from one generation to the next must certainly be almost all, if not entirely, due to environmental change. Flynn presents this as a real-world example that fits Lewontin's model, above, where within-group differences are mostly genetic, while between-group differences are mostly environmental in origin. (This also plays into a continuing current theme in Flynn's research examining how IQ can continue to increase while remaining fairly strongly heritable. This itself appears paradoxical, since continued environmental gains would normally be expected to reduce the heritability by decreasing potential environmental variance.) Second, the magnitude of the IQ gains is so large, that the Black-White average IQ difference seems comparatively minor (15):

As for the environmental gap one must posit to explain the Black-White IQ gap, IQ gains over time pull this out of the stratosphere and down to earth. It appears that Blacks have enjoyed a slightly higher rate of gain on Wechsler-type tests than Whites (Herrnstein and Murray 1994, pp. 277, 289). This implies that since 1945, Blacks have gained at an average rate of over 0.30 points per year and have gained a total of 16 points over 50 years. Therefore, the Blacks of 1995 should have matched the mean IQ of the Whites of 1945. Therefore, an environmental explanation of the racial IQ gap need only posit this: that the average environment for Blacks in 1995 matches the quality of the average environment for Whites in 1945. I do not find that implausible.

Of course, this still leaves unexplained just why the IQ gains have occurred and whether they actually reflect differences in some mental properties beyond the process of psychometry. So as an account of race differences, it is not entirely satisfactory. But it does show quite clearly that the kind of environmental differences that would be sufficient to explain racial differences in IQ as measured today are very much within the range of environmental changes that must have occurred in a historical context. For that reason, we have every reason to think that the environmental differences between groups today might be very large, and sufficient to explain observed differences in IQ scores. Or as Flynn puts it (16): "The appropriate rejection of Black genetic inferiority is this: Nothing at present coerces rational belief."

The penultimate section of Flynn's paper concerns the relationship of IQ with class membership, the thesis of Herrnstein and Murray's The Bell Curve. Here, Flynn does something very interesting (this section is derived from a longer 1996 paper in the Journal of Biosocial Science). Most critiques of The Bell Curve have focused on the race differences aspect of the book. But Flynn takes a greater interest in the aspect of the book that focuses on the idea of a natural meritocracy, for which IQ scores are assumed to be a correlate (16):

[Race differences are] a distraction from the real challenge The Bell Curve poses. The humane-egalitarian concept of social justice includes more than compensating people who suffer because of their group membership. It gives high priority to certain ideals, such as reducing environmental inequality and social privilege to tolerable levels. Herrnstein and Murray (1994) went beyond race to level the most devastating possible critique of those ideals, namely, that they self-destruct in practice. I refer to the meritocracy thesis, which runs as follows. The closer we come to environmental equality, the more all talent differences become caused by genetic differences. The more we eliminate privilege, the more we have total social mobility, and good genes for talent rise to the top and bad genes sink to the bottom. The tendency to marry those of similar IQ produces mating couples whose social status correlates with genetic quality. The result is an elite class whose children replicate their parents' high status, because of luck in the genetic lottery, and a large immiserated underclass whose children, handicapped by their bad genes, cannot escape low status.

Flynn presents an argument against this "meritocracy thesis" that claims the thesis is psychologically incoherent. It is not enough to show that an IQ elite is not already emerging, for although the evidence clearly shows that class differences in IQ are not increasing, that does little to assuage the moral difficulties that emerge from the concept of a true meritocracy. For there can be little argument that a reduction in environmental differences between people is a goal of "enlightened" social policy; it is, after all, the very meaning of "equality of opportunity." If the emergence of strong and permanent class differences based on genetic differences were a natural consequence of true equality of opportunity, one might well question the social value of such policies.

But Flynn argues that the meritocracy thesis is internally incoherent. It proposes that if social and environmental inequalities were eliminated, a strong ordering of people by class according to their innate talents would result. Because of equal environments, variation in talents would be largely genetic, and would therefore be increasingly resistant to change. But consider that social stratification occurs precisely because of the striving of individuals for greater status, wealth, prestige, and other indices of social inequality. Flynn essentially argues that Herrnstein and Murray (1984) unjustifiably project the current value of materialism and elitism into a hypothetical future, one which is predicated on the absence of the current level of materialism and elitism. In other words, the meritocratic future depends on strong notions of social competition based on wealth (or other markers of status), but the establishment of such a future depends on eliminating most differences in wealth and status. Or more directly (18):

The case against meritocracy can also be put sociologically: (a) Allocating rewards irrespective of merit is a prerequisite for meritocracy, otherwise environments cannot be equalized; (b) allocating rewards according to merit is a prerequisite for meritocracy, otherwise people cannot be stratified by wealth and status; (c) therefore, a class-stratified meritocracy is impossible.

Thus, the idea of an "immiserated underclass" seems inconsisent with the assertion that environments are qualitatively equal. But "if all have decent work, housing, education, health care, security in old age, what remains is not essential for happiness. Many people of talent may want more than the not-unattractive minimum, but ho many will care about shaking the last dollar out of the money tree?" (18). Flynn concludes (18):

Analysis of the meritocracy thesis provides not only a rebuttal but also a better understanding of the dynamics of humane-egalitarian ideals. The truth is that we cannot push equality much beyond our capacity to humanize. Every significant step toward equality must be accompanied by an evolution of values unfriendly to success as defined by the present class structure. Humane-egalitarian ideals possess a great glory: a self-correcting mechanism that avoids meritocratic excess. Whatever dark spirits lurk in the depths of equality, meritocracy is not among them.

I find this part the most intriguing, because it invites some expectations about ancient human societies, and the probable correlates of intelligence. Clearly, intelligence (broadly construed) in humans has both genetic and environmental components. Likewise, other traits including status (wealth is less relevant in a Pleistocene context) and of course fitness have both genetic and environmental components. Each of these traits was likely correlated to some extent with the others, and to the extent that each trait was correlated with fitness and was heritable, it would be under selection.

In this context, humans had every reason to increase their fitness through systematic alteration of the environmental component of these traits. Some aspects of the environment would be largely outside their control. For example, maximizing nutrition must have been a constant struggle for all people largely at the mercy of local ecological conditions. Other aspects could have emerged from interesting patterns of social interaction. For example, practical intelligence (as applied to problems of survival and reproduction) must have been greatly influenced by other people, through teaching, observation, learning feedbacks, storytelling, and other opportunities. It seems plausible that the environmental component of this kind of intelligence would have been higher in Pleistocene societies than today. One reason is the likely diversity of social contexts in small groups with high mortality rates (such as the increased chance of absence of one or both parents).

This kind of interaction among variables creates a behavioral context in which not only the brain functions underlying intelligence-related skills would have been under selection, but also those functions related to enabling those functions to their maximum under the existing environmental regime. This latter selection would be highly kin-mediated, as the inclusive fitness of individuals depended partly on the intelligence of their relatives. For that matter, the direct fitness of individuals would depend on the realized intelligence of members of their groups in the long-term struggle for survival and differential reproduction. Consider:

1. These processes predict that group effects in human evolution might have been largely intelligence-mediated. Individual survival depends in part on the hunting effectiveness of group members, on their ability to maintain social ties with kin in neighboring groups, if they remember or not important information about ecological or climatic variability, etc. So it is in every individual's best interest to contribute materially to the education (meaning environmental maximization of operational intelligence) of other members of his or her group, related or not.
2. Any genetic advantages in intelligence mean little without substantial environmental equality within the population at large. This is because environmental differences in intelligence might easily outweigh any genetic advantage.
3. It goes without saying that people should have competed to the greatest extent possible for those material (or behavioral) circumstances that are associated with maximal environmental benefits for fitness. But if intelligence was correlated with fitness, then those circumstances most favorable for the development of intelligence should also have been subject to strong competition. These might include:
   1. preserving the lives of elders or others with valuable information
   2. recruiting new group members with certain properties conducive to greater group learning, such as good storytellers
   3. developing strong cultural justifications for the transmission of certain kinds of knowledge
   4. exercising mate choice based on behaviors related to intelligence
   and certainly others.

These ideas are suggestive. People were not merely involved in a struggle for survival and reproduction, in which intelligence may have been a factor. They were simultaneously locked in a meta-struggle, in which the determinants of intelligence were themselves judged among people and their social standing and other characteristics became dependent on them because of their value for the group, present and future kin, and their risk observed for neighboring peoples. These conditions were only genetic to a minimal extent. For the most part, this struggle took place within populations based on the fundamentally environmental variation that was always present and could not be eliminated (because it would always have been maintained by population pressure if nothing else). So the natural selection underlying the evolution of the brain was itself a side effect of a very powerful social structure with behaviors devoted to detecting intelligence and promoting it for basically selfish reasons.

References:

Flynn JR. 1984. The mean IQ of Americans: massive gains from 1932 to 1978. Psych Bull 95:29-51.

Flynn JR. 1996. Group differences: is the good society impossible? J Biosoc Sci 28:573-585.

Flynn JR. 1999. Searching for justice: the discovery of IQ gains over time. Am Psych 54:5-29.

Jensen AR. 1972. Genetics and education. New York: Harper and Row.