Terence Tao is a 2006 recipient of the Fields Medal. He scored a 760 on the SAT-Math at the age of 8 and reportedly has an IQ exceeding 220. He is probably best known for proving the Green-Tao Theorem:
It is always possible to find, somewhere in the infinity of integers, a progression of prime numbers of equal spacing and any length.
I just came across this absorbing profile of Tao as a young boy. One impression that I take away from this piece is that Tao was blessed with good parents (in many senses).
Here is something that caught my eye over at PLoS ONE:
Most birds have simple genitalia; males lack external genitalia and females have simple vaginas. However, male waterfowl have a phallus whose length (1.5-40 cm) and morphological elaborations vary among species and are positively correlated with the frequency of forced extra-pair copulations among waterfowl species. Here we report morphological complexity in female genital morphology in waterfowl and describe variation vaginal morphology that is unprecedented in birds. This variation comprises two anatomical novelties: (i) dead end sacs, and (ii) clockwise coils. These vaginal structures appear to function to exclude the intromission of the counter-clockwise spiralling male phallus without female cooperation. A phylogenetically controlled comparative analysis of 16 waterfowl species shows that the degree of vaginal elaboration is positively correlated with phallus length, demonstrating that female morphological complexity has co-evolved with male phallus length. Intersexual selection is most likely responsible for the observed coevolution, although identifying the specific mechanism is difficult. Our results suggest that females have evolved a cryptic anatomical mechanism of choice in response to forced extra-pair copulations.
This paper has some interesting figures.
You can see it here. There are no surprises.
With two exceptions, each group shows a balanced profile in that it does no better or worse on Verbal than on Math, after each test has been normed relative to the entire test-taking population. The exceptions are males overall (who do about 30 points better on Math) and the group labeled “Asian, Asian American, or Pacific Islander” (about 70 points better on Math).
The rather large standard deviation of the Asian group suggests that it is in fact composed of two or more distributions. Regardless, the mean Verbal score for Asians is about 20 points lower than that for whites; the mean Math score is about 45 points higher. In fact, Math is too easy for some subgroup of Asians; a perfect 800 places an Asian only in the 98th percentile of his or her group.
The overall sex difference on Math is about 30 points in favor of males.
The white-black difference on the overall score is exactly 200 points. The Asian-black difference on Math alone is nearly 150 points.
Commentary has published an article by Charles Murray on a topic that has received much coverage here at GNXP: the high intelligence of Ashkenazi Jews (see also here, here, and here). He expands the historical and ethnic scope of the discussion in a very provocative way.
Update: Razib takes issue with Charles Murray on some points concerning historical Jewish accomplishment:
The first is the fully realized conceptualization of monotheism, expressed through one of the literary treasures of the world, the Hebrew Bible. It not only laid the foundation for three great religions but, as Thomas Cahill describes in The Gifts of the Jews (1998), introduced a way of looking at the meaning of human life and the nature of history that defines core elements of the modern sensibility. The second achievement is not often treated as a Jewish one but clearly is: Christian theology expressed through the New Testament, an accomplishment that has spilled into every aspect of Western civilization.
i am kind of confused by this (or more precisely, i think this is just wrong). we know who the church fathers who shaped christian theology were. to my knowledge, origen, athanasius, gregory of nazianzus, etc. were not christians of jewish origin. christian theology seems pretty clearly something for which the greek cultural matrix was necessary, and the prime driver. amongst the church fathers the theologians are even invariably greek speakers (latin speakers such as augustine can be considered an exception, but his work is wide ranging and not focused on theology like origen, for example). obviously the jews get some of the credit for being the source of the basic religious ideas, but, there were jews around while christian theology was being developed, but they were apart from it, and it seems that later judaism (e.g., the theology of maimonides) shows the same influence of greek philosophy after a period of acculturation.
as for the first, this is much more defensible. but, anyone who knows about the origin of judaism between the 10th and 2th centuries also knows that the influence of zoroastrian religious ideas were likely critical. so the issue is not as clear cut as charles would make it, though it is quite miraculous that an obscure people could produce a book like the hebrew bible which we cherish to this day.
Update II: Greg Cochran says:
Non-Ashkenazi Jews do not have high IQ scores today: see Lynn and David. Nor is there the slightest sign that that Jews were sharper than average in Classical times: not one single paragraph in preserved classical literature suggests that anyone had that impression. Nor did the Byzantines….
Genetic isolation is a precondition for this kind of selection and I can imagine that it happened in some Jewish group other than the Ashkenazi. The Iberian Jews, if anyone. The same is true for them having mostly urban occupations – it’s a precondition. But that shift hadn’t happened at all by Classical times – it began hundreds of years later and was only more-or-less complete by 800 AD. And only among the Ashkenazi was there a shift to (almost entirely) white-collar jobs. And the effects of any such selection among non-Ashkenazi Jews clearly no longer exist: look at the psychometrics and the occupation/educational pattern in Israel….
One other point: the mutations that look like boosters are mostly new (~1000 years old) as well as being confined to the Ashkenazim.
Charles Murray has an important new paper in press at Intelligence. Here is the abstract:
The black-white difference in test scores for the three standardizations of the Woodcock-Johnson battery of cognitive tests is analyzed in terms of birth cohorts covering the years from 1920 through 1991. Among persons tested at ages 6-65, a narrowing of the difference occurred in overall IQ and in the two most highly g-loaded clusters in the Woodcock-Johnson, Gc and Gf. After controlling for standardization and interaction effects, the magnitude of these reductions is on the order of half a standard deviation from the high point among those born in the 1920s to the low point among those born in the last half of the 1960s and early 1970s. These reductions do not appear for IQ or Gc if the results are restricted to persons born from the mid-1940s onward. The results consistently point to a B-W difference that has increased slightly on all three measures for persons born after the 1960s. The evidence for a high B-W IQ difference among those born in the early part of the 20th century and a subsequent reduction is at odds with other evidence that the B-W IQ difference has remained unchanged. The end to the narrowing of the B-W IQ difference for persons born after the 1960s is consistent with almost all other data that have been analyzed by birth cohort.
What I find rather interesting is the evidence adduced for (1) a much larger IQ gap between blacks and whites (~1.5 standard deviations) in the early part of the twentieth century than has usually been claimed and (2) a subsequent narrowing of this gap to the familiar one standard deviation. However, for various reasons Murray admits that the evidence for this trend is “inconclusive.” A graphical display of the data analyzed by Murray is reproduced below.
The Flynn Effect has done much to convince differential psychologists that there are aspects of the relationship between latent constructs and their indicators that remain poorly understood, including perhaps the partition of within- and between-group phenotypic variance into genetic and environmental sources. However, hereditarians have long granted that certain environmental influences, not operating for the most part within the great bulk of white populations living in modern Western societies, may contribute to observed differences in test scores among racial groups. For example, Arthur Jensen (1998, pp. 495-498) found extremely convincing evidence for potent environmental effects on black IQs in a rural Georgia county where black SES was exceedingly low even relative to other blacks in the US. Older black sibs systematically scored worse on an IQ test than their younger sibs, indicating some environmental insult that accumulated over time. The overall black-white IQ difference of ~30 points in this county would have been reduced to the typical ~15 points if the decrement attributable to this cumulative environmental effect had been removed. Suppose that a much greater proportion of the American black population born earlier in the twentieth century suffered from whatever environmental deficits were responsible for the effects observed in this particular Georgia county. This is perhaps not an unreasonable assumption, given the concentration of the blacks in the rural South at the time. This would account for the trend displayed in the figure above.
I anticipate that more sophisticated psychometric analyses of these data will be forthcoming. In the meantime I have a question that perhaps Dr. Murray might be able to answer for us. In the first two samples, blacks show a larger variance in IQ. This goes against the grain of previous findings. Is this an artifact of the heterogeneity of scores across birth years within the black samples? What happens to the white:black variance ratio if age is held constant?
The paper is available in GNXP Forum.
Wendy Johnson, Thomas Bouchard, and their colleagues have an important paper in press at Intelligence reanalyzing data from the Minnesota Study of Twins Reared Apart (MISTRA). As many of you may be aware, the Minnesota group previously reported a correlation in IQ of 0.75 for 40+ pairs of identical twins reared apart (Bouchard et al., 1990). This implies a broad-sense heritability of 0.75; that is, three quarters of the variance in IQ is ascribable to genetic factors. MISTRA has continued since then, and this latest paper provides an update.
The sample used for this study included 126 twin pairs (74 monozygotic, 52 dizygotic) only. Most of the pairs were separated early in life, reared in adoptive families, and reunited only in adulthood. A few were separated early in life but reared by different biological family members. The twins were primarily from North America, Great Britain, and Australia, though several came from other countries and a few had been raised in different countries. They ranged in age from 18 to 79 years (mean = 42.7, SD = 13.6). Their educational backgrounds varied from less than high school to post-graduate experience, and occupations ranged accordingly.
These subjects were administered over 40 ability tests during their participation in MISTRA. In this reanalysis heritabilities were estimated for g in particular and also for lower-order factors such as verbal ability and image rotation. The heritability of g was estimated to be 0.77 (95% CI: 0.66-0.84). Estimated heritabilities for lower-order factors were also substantial.
The contribution to the correlation between twins caused by similarity in rearing environments was estimated by multiplying the square of the environment-score correlation by the correlation between twins in the environmental measure. It was found that the contributions to the correlation between twins in g by familial cohesion, expressiveness, conflict, independence, achievement orientation, intellectual-cultural orientation, active-recreational orientation, moral-religious emphasis, organization, and control (all dimensions of the Family Environmental Scale) were all zero to within two decimal places. The contributions by family size, parental occupation, parental education, and possessions in the home (including material, cultural, mechanical, and scientific possessions) ranged from zero to 0.02.
In press at The Journal of Biosocial Science is a paper by Hanna David and Richard Lynn reviewing several Israeli studies comparing the IQs of the Ashkenazim to those of Jews from non-European backgrounds. A virtue of the paper is that it brings to light many studies that had originally been published in Hebrew and thus been obscured from the attention of Western differential psychologists.
The results, compiled over the last half century, are so stark that even as notorious a number bumbler as Lynn could not possibly have manufactured the signal. David and Lynn conclude that the Ashkenazim enjoy an IQ advantage of roughly 14 points over their fellow Jews.
Related: Recall that N-acetylaspartate (NAA), a brain metabolite found to correlate positively with IQ and often employed as a marker (by its absence) of brain insult or dysfunction, leads to Canavan disease when an individual is homozygous for a mutation knocking out the enzyme that breaks it down. This mutation is more common among the Ashkenazi Jews than in any other population–an observations that led Cochran, Hardy, and Harpending (2006) to hypothesize that the mutant is in fact an IQ booster. I have found an extremely thorough review of NAA by the neurochemist Morris Baslow (2003). Much of it is over my head, but perhaps the biochemists and neuroscientists among us can make something of it. My impression is that there are several plausible pathways by which NAA might affect the information-processing capacity of neurons and neural networks.
NAA is indeed an important intracellular osmolyte and storage form for brain Asp and Ac. It also participates in the formation of NAAG, supplies Ac to oligodendrocytes that may be incorporated into myelin, and has the potential for functioning as an intercellular signaling molecule, along with its derivative NAAG. However, as a hypothesis that encompasses most of these observations, it is proposed that the NAA cycle serves primarily as a neuronal mechanism to remove large amounts of metabolic water generated in performing its interneuronal and intercellular signaling tasks.
In press at Intelligence, from the redoubtable Ian Deary and his colleagues:
There is scientific and popular dispute about whether there are sex differences in cognitive abilities and whether they are relevant to the proportions of men and women who attain high-level achievements, such as Nobel Prizes. A recent meta-analysis (Lynn, R., and Irwing, P. (2004). Sex differences on the progressive matrices: a meta-analysis. Intelligence, 32, 481-498.), which suggested that males have higher mean scores on the general factor in intelligence (g), proved especially contentious. Here we use a novel design, comparing 1292 pairs of opposite-sex siblings who participated in the US National Longitudinal Survey of Youth 1979 (NLSY1979). The mental test applied was the Armed Services Vocational Aptitude Battery (ASVAB), from which the briefer Armed Forces Qualification Test (AFQT) scores can also be derived. Males have only a marginal advantage in mean levels of g (less than 7% of a standard deviation) from the ASVAB and AFQT, but substantially greater variance. Among the top 2% AFQT scores, there were almost twice as many males as females. These differences could provide a partial basis for sex differences in intellectual eminence.