Narrow Distribution

For American blacks, the variance in IQ and IQ-like tests is significantly smaller than it is in whites – 65-80% as big. You already knew that the mean was ~ 1 std lower. Smaller for IQ, SAT, MCAT, bar exams, CBEST, and ACT.

I don’t know why, and I doubt if anyone does. I had a notion yesterday, but I’m not sure it works.

While I’m at it, another obscure fact: the 1-std difference exists in congenitally deaf kids. Both groups have lower verbal scores than kids with normal hearing, but differ by about 1 std.

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109 Responses to Narrow Distribution

  1. gwern says:

    A floor on IQ tests?

    • gcochran says:

      I don’t think so.

      • gwern says:

        Not sure how you would know about any floor effects if all you have is a summary statistic like variance… Maybe there’s a different floor, those who score way too low are not being sampled – they’re in prisons, institutions, can’t be found, dropped out, that sort of thing.

      • Anonymous says:

        IQ is scaled to be normally distributed. If the underlying “raw” intelligence is heavier tailed, with different means but with the same variance in each population, then the non-linear rescaling to get to normality would decrease the variance of blacks.

  2. Peter Johnson says:

    The last paragraph is unclear to me, in particular there is an unclear reference to “the two groups”.

  3. Curious says:

    Could you give the citation in cases like this? Or at least enough info for easy Googling? It would help your readers a lot.

    • gcochran says:

      Deafness, Deprivation, and IQ
      By Jeffery P. Braden p 187

      “The black SD of IQ is approximately 12, ranging in most samples from 11 to 14″

      p. 353, The g Factor

      • Curious says:


      • dave chamberlin says:

        There should be a “stooge effect” from the scientific community trying to find out what causes the large variation in human inteligence. Why? Because it is very real and very large and very genetic. When we find that out then it’s Katie-bar-the-door for fixing stoopid ect ect. I find it sad and dissapointing that Jensen’s book the G Factor is now fifteen years old and it still isn’t outdated by preceeding books that have moved the science studying human intelligence forward. I want my own copy but it is of such limited publication that it costs over 100 bucks new and 60 bucks used.

  4. Pincher Martin says:

    “I don’t know why, and I doubt if anyone does. I had a notion yesterday, but I’m not sure it works.”

    Care to share your provisional idea?

    • gcochran says:

      It is not really a clear idea, more the suspicion that some of the facts we know ought to come together in a way that would explain most of the phenomenon. Such suspicions occasionally lead to something. The smaller standard deviation, if real, might be a clue.

      What do we know? There’s a ~1 std difference in means. Black std is smaller, maybe 0.8 of white std.

      if we’re thinking about genetic load in a fairly simple way (just paternal age), we expect to see materially higher burden of mild deleterious mutations in blacks, due to polygamy in their ancestors. Say mutations that have an effect of 1%. And there is indeed evidence of more load. The burden of deleterious mutations with large effect (5% and up) should not be much different: blacks in the US have had ~200 years free of high paternal age.

      Then there is the funny-looking kid effect. As IQ gets lower and lower, a higher and higher fraction of kids are funny-looking. Seems to me that such cases are caused by single (or very few) pleiotropic deleterious mutations of large effect. But then, you can also find kids with the same IQ who aren’t funny-looking. This kind of MR, on the whole milder than the FLK kind, is usually called familial MR. It’s plenty heritable, but FLK MR is much less so. Some of it is probably recessive, some is denovo. Obviously, to the extent that a disorder is caused by a de novo mutation, there is no causal genetic similarity between parent and child or between sibs…

      Familial MR looks to be caused by a greater-than-usual number of mildly deleterious mutations. Thus plenty heritable. Wouldn’t make you particularly funny looking, because although pleiotropic effects must exist, you’re summing over many independent ones, mostly they cancel out. Random walk rather than one big jump in phenotype space.

      We also know that at IQ 70, a higher fraction of white kids are funny-looking than black kids. Suggest the possibility that the black-white gap is caused by differences in the amount of mild load. Maybe. The differences in the amount of mild load do seem to exist, and more load can’t be good. It clearly isn’t caused by differences in large-effect load.

      The increasing fraction of FLKs at lower IQ suggests that the IQ distribution generated by variation in the number of of mild mutations is narrower than that generated by single deleterious mutations of large effect. Which makes sense. Central limit theorem.

      • Pincher Martin says:

        Jensen has something in the The g Factor about observing a higher percentage of FLKs among low IQ white children compared to black children in the same low IQ range. He notes that many low IQ black children seem to function fine outside of the classroom; they have none (or few) of the obvious social and physical handicaps that many of their low IQ white peers have. A black child with a 70 IQ, for example, can appear happy and well-adjusted out in the schoolyard at recess; his white peer is far more likely to have some obvious problem that is apparent in his physical appearance and how he socializes with other children.

        I can’t recall if Jensen attempts a guess as to why this is so, and I don’t have the book in front of me right now, but I don’t remember him going beyond observation. I like your attempt to make some sense of what he was seeing. Let us know how it goes.

        “What do we know? There’s a ~1 std difference in means. Black std is smaller, maybe 0.8 of white std.”

        What about hybridization? Shouldn’t the greater possible variance in black Americans’ degree of white ancestry also cause the black std to slightly widen, all other things equal?

        In other words, isn’t the measured black std (0.8) not just smaller than the white std (~1.0), but also smaller than what we should assume given the greater hybridization of African Americans relative to white Americans?

      • gcochran9 says:

        variation in admixture increasing the variance. You’d think so. But here we are. I have no info on the variance in Africa.

      • Paul N. says:

        FLK, I can understand from the context. But please explain what is funny in your language is it ugly or pretty, is it repelling or attractive.

        MR? I cannot figure out what that means.

        post scriptum (PS): it often is a good idea to put the acronym in parenthesis after the first usage of a phrase.

      • The fourth doorman of the apocalypse says:

        variation in admixture increasing the variance. You’d think so. But here we are. I have no info on the variance in Africa.

        Is it reasonable to assume that all (or almost all) extant humans are playing with the same set of genes that affect IQ?

        If so, then aren’t we simply talking about different numbers of genes from that set that have gone to fixation in each of those populations, and the more that have gone to fixation in a population the lower the variance?

      • Murray Anderson says:

        The number of mildly deleterious mutations would follow a Poisson distribution, more or less, so the mean would equal the variance. The population with more mildly deleterious mutations would have higher trait variance, at least in respect of those sorts of mutations.

      • Steve Sailer says:

        But the smaller standard deviation also implies proportionately fewer blacks at the high end, which, indeed, appears to be true. And that doesn’t strike me as fitting in well with the random minor load hypothesis.

      • gcochran9 says:

        “random minor load hypothesis.”

        A population with more genetic load would certainly have fewer high-scoring individuals. Either I’m not getting your point or you’re not getting mine.

      • Steve Sailer says:

        For Paul N: “FLK” is American doctor shorthand for “Funny Looking Kid” — e.g., Down’s Syndrome.

      • Paul N. says:

        @Steve Sailer
        Thank you very kind of you to answer my questions.
        That makes sense. Then of course MR is mental retardation.

  5. James Thompson says:

    Well, I give up. How about a clue? For example, what causes variance anyway? It cannot just be error, so there must be a functional driver somewhere.Monotonic, not stochastic. Was there a bottleneck event in African slave history, and a commensurate bottleneck in severe deafness?

  6. Mike Johnson says:

    What if we estimate variance as a percentage of average scores rather than absolute points? E.g., group one averages 120 with a standard deviation of 18, group two averages 100 with a std of 15, group three averages 80 with a std of 12. It looks like group one has a much higher variance, but percentage-wise all groups are identical.

    The issue GC brings up doesn’t disappear under this analysis, but it does appear to shrink(?).

    • Anthony says:

      That would make more sense if IQ were a “score” rather than a point on a distribution. A person with IQ 108 isn’t (necesssarily) 20% more intelligent, or faster-thinking, or more capable of complex abstraction, or any other g-loaded task than one with an IQ of 90. An IQ of 90 means that your score on some test was 2/3 s.d. below the average for white Americans (or white Britons). A score of 108 means your score was .53 s.d. more than that same average.

  7. Social Pengler says:

    well, one thing to remember that a white kid, at 70 IQ, is 2 full standard deviations out. a black kid is what, 1.4? so the amount of work to get him that far out is much less, bringin less Other Problems with it…

  8. The fourth doorman of the apocalypse says:


    If you assume that more genes are fixed at lower or zero IQ point producing alleles in that population (and assuming a simple model) a reduced variance seems explained.

  9. Sid says:

    Is there information on Khoisan IQ variance? Information on IQ variance amongst the Australoids? If the IQ variance of Australoids is similar to that among Europeans, while the Khoisan have similar IQ variance to blacks, then the wider bell curve amongst blacks and the Khoisan may very well be an African phenomenon. If Australoids also have narrow IQ variance, then it is likely to be a matter relating to genetic load. If blacks have a narrow IQ variance, while the Khoisan have a wide bell curve, then something peculiar in the evolutionary history of blacks has given them such a characteristic.

    (If memory serves, Asians have similar IQ variance as whites: a std of 15 or so.)

  10. Jack Thorne says:

    A quick question about IQ, I’d like to know what y’all think:

    In my experience, there are two kinds of people (with a little exaggeration of course): those who like to solve IQ tests and those who get bored with them after 5-10 minutes (which obviously results in performing under one’s potential). Now, which group one belongs to is not correlated with success in school for instance. Some people just happen to like those tedious IQ tests while others don’t, let’s call this phenomenon a difference in tastes.

    Therefore, one’s performance on IQ tests is influenced by this difference in tastes. Now I don’t know what causes such a difference but that’s not important now. Isn’t it possible that certain groups (f.e. African Americans) happen to dislike IQ tests because their tastes on average are different?

    Another interesting thing I noticed is that if someone likes puzzles (crossword, sudoku, mathematical problems, etc.), this doesn’t automatically mean that they will like solving IQ tests. Matter of fact, it seems to be uncorrelated.

    Of course these are just personal experiences/observations, but I still find them interesting and relevant.

    Any thoughts?

    • ziel says:

      You’re suggesting that there is something in the character of IQ tests per se that one group of people might find boring, as opposed to different kinds of tests that would also measure intelligence? Problem is, the same 1 std gap is found on all kinds of tests.

      Think about it – there’s essentially a $1b prize sitting out there waiting for someone who could devise a test that could reliably measure intelligence and not show any significant racial gap. Every organization looking for a low-cost way to identify talented people without disparate impact – which is every organization in North America – would subscribe. I think that if the way around the problem were simply to figure out how to keep African-Americans from getting bored with the test, it would be solved by now.

      The only rational explanation for why the gap exists is that it is real – and you can’t get rid of the testing gap without also getting rid of the test’s utility.

    • bruce says:

      The Porteus Maze test was a ‘trail your pen through this maze’ test, florit 1920s-1950s. Porteus said it topped out at 130 IQ: he got in trouble with liberals for testing some Austrailian aborigines. No idea how modern IQ researchers think of his test.

      Anyone know where would I look for variation among Jews and Asians on the one hand, United States Marines on the other?

    • James Thompson says:

      In that case the IQ results of the “bored” kids would under-predict their other achievements. Have you any evidence of this? Jensen found that IQ tests did not under-predict Black achievement in the US, If anything they very slightly over-predicted. The 1 sd gap is generally accepted, but there is argument about data relating to more recent times for IQ. Scholastic gaps closed somewhat in the 80s to about 0.7 sd, but remained at roughly that gap thereafter, using NAEP datat. Mexicans also came up on that measure at roughly the same time. I don’t have data to hand on the SD of their IQs.

    • Josh says:

      In addition to the other responses some researchers have also looked at using elementary cogntive task measures to reduce possible issues of motivation/interest.

      eg. Pesta, B., & Poznanski, P. (2008). Black-White differences on IQ and grades: The mediating role of elementary cognitive tasks. Intelligence, 36, 323-329.

  11. Matt says:

    Any confirmation online that this is the case for the SAT? The logic makes perfect sense however the SAT and NAEP data explorer checks I’ve done a quick search for find Blacks at around 95-99% ST of Whites (with Asian / Pacific Islander showing the real major SD increases)


    Total Distribution
    Black SD – 98-94 depending on subtest, Mexcian SD – 97-92, White – 103 SD, Asian Asian American, or Pacific Islander.SD – 125 to 129.

    The NAEP’s grade 12 mathematics is likewise, Black SD – 30, White SD – 31, Hispanic SD – 30, Asian/Pacific Islander SD – 34

    • gcochran9 says:

      The IQ distribution I’m sure of, the result for other tests are second hand – recent information from a presumably reliably source. So they may be wrong.

      On the other hand, SAT-takers are not anything close to a representative sample.

    • nooffensebut says:

      I graphed SAT SD by race for each available year. Black SDs were lower than those of whites for most years, critical reading in the late 90s to early 00s being the exception. Asians recently increased a little but are still not at mid-80s levels.

  12. Toad says:

    American whites is a bigger tent including a larger number of ethnics. Irish, Spanish, British, Germans etc, all in the room taking the test. American blacks includes a narrower range of ethnics, mostly from west Africa.

    The same study done in England might have different results. The whites would mostly be British, and the blacks would come from a wider variety of home country.

  13. James Thompson says:

    Jensen’s observations on black-white difference in MR is set out on pages 367-369 of the g factor. White MR kids were less socially competent, more motorically clumsy or awkward, or walked with flat footed gait. Jensen’s explanation, briefly, is that more white kids got MR by organic problems than black kids, most of the latter being there because of the normal distribution of intelligence around a lower mean. Same explanation as given by Galton in 1892 in Hereditary Genius “a certain proportion of them are idiotic, owing to some fortuitous cause, which may interfere with the working of a naturally good brain, much as a bit of dirt may cause a first-rate chronometer to keep worse time than an ordinary watch”.

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  15. L says:

    BTW, SSI/SSDI treats a black with an IQ of 70 who is socially and physically normal, EXACTLY the same as a flat-footed, uncoordinated, socially awkward (FLK) white kid with an IQ of 70. Yes, these kids are sent to be IQ tested when their parents apply for disability, and otherwise normal black kids who are around 1 SD below the AA mean (and who are often bullies and troublemakers) are put on benefits until they’re 18, if not for life, every single day of the work week every week of the year.

    To not do so is to admit the 1SD B/W difference exists, and we can’t have that!

  16. Curious says:

    Greg, could you say something about this paper?

    • gcochran9 says:

      It’s good to know that Jonathan Kane loves his Mom.

      A commenter here estimated that at least 3, but probably less than 10, of the top 1000 mathematicians of the 20th century were women. From what I know about this, any mathematics department would cheerfully hire a banana slug if he/she proved Goldbach’s conjecture. Being a nut does not interfere much with getting a job, as long as you can do the work, and don’t kill more people than you solve Hilbert problems.

      Mathematics is almost perfectly open to talent. Mathematicians are quite happy to welcome a provincial baker with one year of formal education, or an Indian clerk.

      As far as this question goes, I’m from Missouri.

      • Douglas Knight says:

        The estimate you mention is here. Maybe Jim can’t, but I can very easily name 10 women in the top 1000 mathematicians of 20th century. One problem with this exercise is that neither of us has actually made a list of 1000. MacTutor has made such a list and they have singled out the women. They have 1122 mathematicians born after 1880, including 102 women; 82/805 born after 1900; 41/367 after 1920; 17/91 born after 1940.

        This list might be biased, but at least it is a list. It gives both a numerator and a denominator. It tells us what top 1000 really means. You have to go pretty obscure to get there.

    • misdreavus says:

      Well, here comes the equalitarian brigade once again, exhausting the same old arguments in defense of the notion that heredity makes no contribution to gender differences in behavior.

      In his paper, Kane remarks approvingly of a study by Guiso et al., which purportedly demonstrates a strong negative correlation between international performance on an index of gender equality, and the ratio of female to male students who exceed the 95th percentile for their nation on PISA math scores. [1] In other words, the higher the participation of females in the government and the workforce, the closer the ratio of female to male scorers above the 95th percentile approaches unity. Presto! Gender differences in mathematical ability are a social artifact, nothing more.

      With the exclusion of rampant cheating, note that there are two ways of busting gaps between two populations for which there exist documented and _intractable_ differences in academic performance. (E.g. Blacks and whites in the United States.) For one, you can assess group performance through exams that are so facile that just about everybody performs better across the spectrum. The psychologist Joseph Fagan once published a study demonstrating just that. Apparently, when you administer verbal IQ tests to black and white children along with handy algorithms that provide the answer to nearly all the difficult problems (this, by the way, is supposed to control for “cultural bias” — just WTF?), the IQ gap among black and white children magically diminishes to zero. [2] Well no shit, Sherlock. Now, this phenomenon is supposed to be revelatory to _whom_, exactly? Arthur Jensen? Hans Eysenck? Jorg Haider? How convenient that test scores no longer matter once you destroy the predictive value of test scores. Jesus, my four year old cousin could have told him that.

      Why do I mention this? While there indeed exist documented differences in PISA math performance among OECD nations, the PISA math exam itself is itself an assessment of baseline performance in math at age 15, with questions ranging from easy to moderate difficulty. If you don’t believe me, just consult them for yourself. Guiso et al. insist otherwise, and here is their line of reasoning:

      To verify whether PISA is a challenging test for students, we analyzed the U.S. students’ results in details and compared them with other studies based on challenging tests in the U.S.A. In mathematics, U.S. students ranked 26th out of 40 countries, and this ranking was not only due to a large proportion of poor performers. The United States had a below-average number of top performers: Only 0.6% of the U.S. students tested perform at the 99th percentile of the world distribution. This result shows that PISA is not a minimal competency test. [1]

      Have your eyes rolled out of their sockets yet? There no words for this sort of statistical legerdemain.

      The PISA does a piss-poor job assessing math performance at higher levels of ability, which is what exams like the AMC 12 were designed to do. Hence you should expect a correlation between female participation in the workforce, etc. and a closing of the gender gap at the 95th percentile — because that 95th percentile never meant jack shit, to begin with. What do all advanced, industrialized economies have in common, other than the collective pursuit of the delusion that intelligent women should forsake childbearing to advance their careers? (Hint: Richard Lynn and Vanhanen wrote an entire book on this subject.)

      Well, you can think of it this way. The predictive value of even an easy problem starts to grow monotonically once you reduce the threshold of individuals capable of achieving high scores. All of a sudden, once you move to a rathole like El Salvador, the fraction of individuals who guess the right answer to an easy algebra problem starts to diminish, and so you achieve a greater diversity of responses. By doing so, you’ve changed the Gaussian distribution in a big way, not just by reducing the central value. And for some darned strange reason, all of the correct answers tend to be correlated (gee, why might this be?) — hence you should see a greater proportion of males above the 95th percentile from a low-achieving population.

      Janet Hyde, from whom Kane and Mertz apparently take marching orders, makes a big deal out of the fact that there aren’t meaningful gender differences in performance on the math portion of the NAEP, [3] As if it were a total mystery why girls are just as capable of learning the square root of 64 as boys. Her paper got published in Science, of all places, and was trumpeted just about everywhere in the media, from the New York Times to the Washington Post and Newsweek. Sharon Begley must have creamed her dry undergarments in ecstasy when she first reported the news. (And, by the way, for obvious reasons, racial gaps on the NAEP are not as severe what you might expect from IQ differences.)

      [1] Science 320 (2008), 1164–1165
      [2] Intelligence 35 (2007), 319–334
      [3] Science 25 321 (2008), 494-495

    • misdreavus says:

      Kane also relies heavily on TIMSS data, which are even worse than the PISA — the age of test recipients ranges from elementary to middle school, at a time when sexual dimorphism of _all_ sorts is lower for our species.

      Equalitarians make a big deal out of the fact that sex differences in math performance are trivial in elementary school, expand during middle school, and reach their peak at the cusp of adolescence. This is supposed to demonstrate that socialization is responsible for the ensuing divergence in life outcomes. Because, you see, if they were so similar before, and so different now, when their genes haven’t changed in the meantime, what else might fully account for the difference? Maybe patriarchy is responsible, after all, for the fact that girls develop breasts at age 13, when they once had none, and the fact that boys develop facial hair during late adolescence, after a long period when both sexes were equally hirsute.

      (You know, I have a friend who had a full head of hair at age 18, but was completely bald by his mid-twenties. Maybe it’s because of something he ate.)

      Back to the Hyde study, Janet Hyde points out that because the sex ratio among Asians in Minnesota who score above the state-wide 95th percentile on an assessment test is closer to unity, cultural factors must be responsible. Well that’s just dumb. If you isolated Ashkenazi Jews, you’d probably find a ratio even _closer_ to 1.0 at the 95th percentile. Have they figured out why yet?

      Back in Korea, there is a popular saying among men: “Both dried fish and women must be beaten once every three days”. Well, if Asian culture is responsible for closing the gap, then perhaps we should all beat the shit out of our daughters.

      Hyde routinely commits statistical blunders as obvious as this, yet when you look at the trail of citations, you see nothing but the rankest of sycophancy and rhetorical sleight of hand. Peer review in the human sciences is a complete joke.

      This passage from the Kane and Mertz paper is particularly revealing:

      Noteworthy is the fact that 26 and 27 percent of the girls and boys, respectively, from Shanghai, China, scored above 669 on the 2009 PISA; the corresponding numbers for the U.S. girls and boys were 1.2 and 2.5 percent, respectively, below the 2.8 percent overall for OECD countries. Thus mathematics performance at the low, median, and high levels for both boys and girls strongly correlates with equity indexes;
      gender inequity may be one of the reasons boys do poorly in some wealthy countries.

      This finding explains why equity indexes and gender gap in mean mathematics performance do not reproducibly correlate; that is, while girls’ scores increase as equity indexes increase, boys’ scores do likewise.

      Once you leave out the oil-rich sheikdoms, all of which have provided convenience samples, even their TIMSS data suggests that boys have a larger variance than girls across the board.

    • misdreavus says:

      Lastly, just in case I haven’t bored everyone to tears yet, here’s the other way you can magically close gaps in academic performance. Administer tests that are so difficult that just about everybody is bound to fail, and such that differences in ability below an extreme threshold make little contribution to student outcomes.

      If we administered the Putnam exam to a random sample of 1000 boys and 1000 girls at the age of 17, you’d probably find no difference in mean scores, and given the resolution typical of most papers in the social sciences, not even a statistically significant difference in outcomes past the 95th percentile.

      Yet strangely, in the United States, at least, the vast majority of high scorers on the Putnam are men. Same for the AMC 12, the U.S. Math Olympiad, the AIME, and even the SAT, which has been dumbed down numerous times to assuage the guilt of egalitarian well-wishers. To this day, not a single woman has won the prestigious Fields medal.

      I wonder if this phenomenon has been replicated worldwide. Maybe X-chromosome inactivation in the human species works differently in Laos or Burundi.

      • The fourth doorman of the apocalypse says:

        Your comments are so interesting that I often think that you are the most insane gay person I have ever read. Indeed, I tend to doubt your claims that you are gay, but that is not relevant here.

        When you are talking about the top candidates, what matters, it seems to me, is the variance in each sex, and it is well established, I believe, that the male variance in IQ is larger than the female variance.

        What kind of genetic mechanism would cause such a situation? If we think of IQ as resulting from the action of hundreds of (a hundred or more) genes, what mechanism(s) would cause this?

        Is it possible that hormones produced by the presence of a Y chromosome switches on some genes? However, that would seem to only increase the mean. In addition, it seems that testosterone is converted to estrogen in male brains, so women would seem to have had that switch operating as well.

        Perhaps it is a reflection of my IQ, but I am having problems thinking of a mechanism at the moment.

      • gcochran9 says:

        Try 1 X chromosome instead of 2.

      • James Thompson says:

        Yes, the list of Putnam winners seems to be exclusively male. I note with a smile that “Since 1992, the Elizabeth Lowell Putnam Award has been available to be awarded to a female participant with a high score.” Not a specific score, mind you, but a high score.

      • The fourth doorman of the apocalypse says:

        I wonder if this phenomenon has been replicated worldwide. Maybe X-chromosome inactivation in the human species works differently in Laos or Burundi.

        I read somewhere that not all genes on the inactivated chromosome are silent. Something like 10+% are not silenced. Perhaps I misunderstood what I read, but if not, there might be variance in which genes are inactivated allowing women from Laos to be more intelligent than women from Burundi, for example.

      • misdreavus says:

        @The fourth doorman

        Thank you, but the last time I checked, I am about as queer as a seven dollar bill. I consider myself the self-appointed Uncle Ruckus of the LGBT community. It’s a thankless job, but somebody has to do it — even if he has does have an impairment in the hypothalamus.

        You see, I belong to a generation of college students that has been spoon-fed preposterous lies about human nature from the cradle. (But hell, has there ever been a generation in this country when this _wasn’t_ the case?) Let’s see, “AIDS is a disease that doesn’t discriminate”, “gender is a social construct”, “biological sex is a spectrum, not a dichotomy”, “race has no biological meaning”, “the cure for gender dysphoria is sexual mutilation”, “diversity is our strength”, “illegal hispanic immigration will culturally enrich the United States”, “homosexuality is hereditary and inborn”, et al. Wrong, wrong, wrong I say! Sometimes you feel like shouting to the rooftops so that everyone can hear the truth loud and clear, even if they may be too wool-headed to appreciate it.

        As for gay men, surely they deserve the truth more than anybody else. We’ve had to deal with hatred and nauseating ignorance from religious loons, who, by odd circumstance, happen to be closer to the mark on issues such as this, but are generally too stupid to reason their way out of a wet bathroom stall. (And in the case of Larry Craig and many others, quite literally.) They sometimes are right, but they never seem to understand just why they happen to be right. The level of dysfunctional behavior among homosexual men is truly nauseating to behold — I could go on and on about “gay parents” bringing their “children” to open-air BDSM shows in San Francisco, “bug chasing”, the rampant promiscuity and drug abuse, the domestic violence and cattiness, the discrepancy between the clean-cut image they present to foolish liberals and the sordidness of their actual sexual behavior, etc.
        Worst of all, nobody will challenge them for their sexual profligacy because gays have firmly established themselves as a victim class in America. I present to you the “New Normal” in the year 2013:

        Two-year-olds Zola and Veronica Kruschel waddled through Folsom Street Fair amidst strangers in fishnets and leather crotch pouches, semi and fully nude men.

        The twin girls who were also dressed for the event wore identical lace blouses, floral bonnets and black leather collars purchased from a pet store.

        Fathers Gary Beuschel and John Kruse watched over them closely. They were proud to show the twins off.

        Evolutionary adaptation my ass! How the hell is a disorder like this supposed to help your genes, your nieces and nephews, the tribe, or anybody else? Has the entire world gone insane?

        This abominable behavior doesn’t go away in countries where “institutionalized homophobia” is a thing of the past, either. Consider Denmark, a secular country that legalized same-sex unions during the 1980s, months before I was even born. If homophobia is to blame for dysfunctional behavior among gay men, why are rates of attempted suicide, bipolar disorder, depression, etc. for homosexuals sky high there as well as here? Controlling for ethnicity, why are HIV infection rates among gay men in the United States about the same as they are in western Europe? Then again, the same people who preach this mendacious nonsense also believe that white privilege is responsible for Detroit turning into Little Monrovia within the span of a generation.

        Well to that, I can attest that I may not have been born with my condition, but that other people were probably born with theirs. Interpret that however you will.

        By the way, with the exception of food contamination, most spontaneous outbreaks of “third world diseases” in the developed world like giardiasis, typhoid fever, and amebiasis may be attributed to gay men. If you’re curious, you can google how one can acquire such a pathogen.

      • misdreavus says:

        As for X-chromosomes, my comment was tongue-in-cheek.

        Realize that men not only have a higher variance for IQ, but all sorts of cognitive traits you can think of, inasmuch as they can be measured through psychometric testing.

        Feminists and their sycophants are fond of pointing out obscure regions of the globe where girls outperform boys in mathematics, or where there isn’t much of a difference in the variance ratio — all of which, of course, fall apart under closer scrutiny. You can’t blame them for wishing it were so — if the bell curves were nearly identical somewhere, this would ostensibly prove that our Eurocentric, patriarchal culture is responsible for the dearth of female Teichmullers and Ramachandrans. Total bullcrap.

        You might expect, a priori, that heredity is responsible for most of the difference. Why? This is may be a shoddy caricature of the underlying molecular biology, but men tend to get a double dosage of whatever genes exist on the X-chromosome, to begin with. These include both bad and good alleles, hence a greater proportion of both mental retards and geniuses among men.

        But then again, maybe X-chromosome inactivation does work in a fundamentally different manner in the highlands of Papua New Guinea. Maybe it’s all epigenetics! (snort) Maybe you could active the proper methylation patterns in the womb by solving differential equations while pregnant with your dauther. Someday, through social revolution, we may finally see a Jane von Neumann in the near future.

      • misdreavus says:

        *Sorry, that’s difference between the variances.

  17. panjoomby says:

    in the test publishing industry we get the same, blacks always 1 std dev lower & smaller std dev. not surprising (e.g., mentally retarded – outdated term, i know – have smaller standard deviation – of course!) the lower your group is, the less room to vary! we trumpet “there is more genetic diversity among blacks than whites” – BUT THERE IS MORE MENTAL-INTELLECTUAL diversity among whites (i.e., a larger standard deviation).

  18. Jaim Jota says:

    MILD DELETERIOUS MUTATIONS must be different in Blacks (good athlethere) and Whites (FLKs).

  19. Jaim Jota says:

    I mean that there are many excellent Black athletes with IQ70 while White IQ70 kids suffer generally from motor coordination deficiencies and are FLKs. Their burdens are composed by different sets of MDMs.

    • gcochran9 says:

      The idea is that the brain, being more complicated, may be more susceptible to genetic load than other organs or systems. If you consider the high prevalence of mental retardation and schizophrenia, compared to deafness, this appears to be the case. Or if you look at the spectrum of problems in the children of older fathers – many involve the brain.

      That said, if selection were strong enough, it could compensate for a higher mutation rate, up to some point. And the strength of selection acting on a particular trait is not going to be the same at all times and places.

      I am hardly ruling out selection as a possible causal factor in differences between populations. But when the mutation rate is 30-50% higher in group A than in group B, you need to consider that too, which nobody has ever done. Except for me.

      • tommy says:

        Reading your previous comments on the thread, I’m not understanding your idea. Maybe you can help me.

        All things equal, in the absence of selective pressures, I’d expect that while greater rates of mutation (or greater retention rates for mutations) might indeed correlate with a lower mean when it comes to an additive trait involving a heavily optimized system like the brain, it would also tend to be associated with greater variance in a population. I’d imagine that greater genetic diversity = high variance. What am I missing here?

  20. tommy says:

    Wouldn’t the simultaneous elimination of both higher and lower IQ individuals in a population tend to reduce variance? Perhaps there is a correlation between altruism and IQ variance in populations.

  21. namae nanka says:

    “MacTutor has made such a list and they have singled out the women.”

    It doesn’t give one confidence to see Lovelace in there. Hopefully she is the exception and not the norm in that list.

    “Janet Hyde points out that because the sex ratio among Asians in Minnesota who score above the state-wide 95th percentile on an assessment test is closer to unity, cultural factors must be responsible. ”

    SAT-M 800 is 96th percentile score for asians. Even lower considering the category used.

    “Janet Hyde, from whom Kane and Mertz apparently take marching orders, ”

    La Griffe described her as a “veteran gap buster”,

    • The fourth doorman of the apocalypse says:

      It doesn’t give one confidence to see Lovelace in there. Hopefully she is the exception and not the norm in that list.

      Wow, a porn star and a mathematician. What are the odds?

      Oh, wait. Different century, eh?

  22. Homeless Afrodisiac says:

    Read the comments:
    The internet is catching on.

    • misdreavus says:

      I hope you paid for that book!

    • misdreavus says:

      As far as PDF torrents go, that’s not an unimpressive for something that isn’t porno or pulp fiction.

    • gcochran9 says:

      If you have posting privileges there, you might point out that illegal downloaders of our book who make reasonable contributions to this blog – say 3 dollars (thru Paypal) – might avert fairly serious negative consequences. Once there was a guy who occasionally beat me up in high school, until he tried to take a curve at 120 mph, rolled, and burned to death. There were the two brothers who used to chase me home from elementary school: their mother, while running off with someone, tried to beat the train at the crossing. Distributed all over the football practice field. I could go on. Get the hint?

      • JLikens says:

        If there was an option to like a post, I would like this one.
        I paid full price for the book, as everybody else should.
        Anybody who does not, yet obtains a copy, deserves the full extent of what’s coming to them.

      • Jaim Jota says:

        The good Mr JLikens may have felt intimidated to pay. Not we Hispanos. We kiss a medal of La Niña Blanca (entre-nous, La Santisima Muerte) and nothing can harm us. Sorry, but I cant guarantee that she also protects WASPs.

      • Sideways says:

        This just got me to look up the book at the library. Of the six in the region stocking it, five have it as 599, which is zoological sciences (mammals). Only one has it as 576 (genetics/evolution).

  23. On the “funny looking kid” issue–I first read about this in La Griffe, here:

    Among blacks and whites with comparable cognitive deficits, blacks generally show a better ability to adapt to the rigors of everyday life. The difference is pronounced. Arthur Jensen observed in The g Factor that black pupils with IQ deficiencies often socially integrate well with their brighter peers. They seem quite normal when engaging in non-cerebral activities like play. In contrast, many cognitively impaired white children have difficulty integrating socially and often have physical abnormalities such as flat-footed gaits. Jensen attributes this racial divergence to different etiologies that are transparent to IQ tests.

    Two types of mental retardation can be differentiated. Organic retardation is due to a genetic anomaly or brain damage brought about by disease or trauma. Familial retardation results from normal variations in intelligence. Among whites with IQ < 70, between 25 and 50 percent are diagnosed as organic. Since 2 percent of whites have IQ < 70, 0.5 to 1.0 percent of the entire white population is organically retarded. Jensen estimates that of the blacks with IQ < 70, only 12.5 percent are organically retarded. (We estimate the number closer to 16.7 percent.) Thus for blacks, we expect 16.7 percent of the 12 percent with IQs < 70 to have organic etiologies. That is, about 2.0 percent of the black population at large is organically retarded.

    So are you saying that the organically retarded kids are the funny looking ones, and the ones that function socially are those with familial retardation?

    Has anyone confirmed this? That is 1) the differentiation between FLK and nonFLK is the difference between organic and familial retardation, and 2), the incidence of higher functioning blacks with low IQs is due to the lower frequency of organic retardation among blacks?

  24. Jim says:

    I took a quick glance at the MacTutor list. I didn’t recognize most of the names listed. They are not all twentieth century names. If Kowalewski were a twentiieth century mathematician I would certainly include her in a list of the top 1000 mathemticansof the twentieth century. I didn’t mention her because I consider her a nineteenth century mathematican. Hypatia was one of the names listed but we don’t possess a single surviving line of her writings so there is no way to evaluate her as a mathematican. Ruth Moufang is listed. Now Moufang planes are certainly of interest but if someone seriously considers Ruth Moufang to be one of the top 1000 mathematicians of the twentieth century they are nuts.
    Now you may not not trust my offhand opinion so consider this. I did a quick count of the cited names in Dieudonne’s – History of Algebraic and Differential Topology 1900-1960. The count came to 243 names including two citations for “N. Bourbaki”. Looking through the list I found “E. Noether”
    with three citations and “R. Moufang” with one citation (which turned out to be a footnote). All others were men. So 2 names out of 243 is about one percent.
    “E. Noether” was cited on three pages. “H. Hopf” was cited on 116 pages.

    • Douglas Knight says:

      The list includes 102 women born after 1880 and 25 before.

      Sure, you don’t recognize of a lot of the women, but how many of the men do you recognize?

      1900-1960, “of the 20th century,” and born after 1880 are three different categories. Surely we expect increasing proportions of women.

  25. Jaim Jota says:

    I understand the FLK issue the same way as Educationrealist little above. gcochran – in the improbable case that I didnt misunderstood him – seems to say that slightly deleterious mutations affect mostly the brain in Whites and mostly less complex organs in Blacks. This seems reasonable but let me as a stupid question: Is the brain really more complex than the delicately balanced hormonal system? When breaking down apparently complex software, one discovers that they are built by the repetition of a few basic routines and they are not complicated at all. Maybe the brain is one of the simplest organ of all and therefore more sensitive to sightly deleterous mutations.

  26. The fourth doorman of the apocalypse says:

    I asked:

    What kind of genetic mechanism would cause such a situation? If we think of IQ as resulting from the action of hundreds of (a hundred or more) genes, what mechanism(s) would cause this?

    and Greg responded with:

    Try 1X chromosome instead of 2

    Thank you.

    That would certainly seem to have an impact. However, while it would seem to mean that fewer women than men would be impacted by receiving a lower IQ producing gene variant (and women would harbor more defective alleles) does it really impact the RHS of the curve?

    Hmmm, in a Binomial distribution, Npq is smaller if p!=q than it would be if p==q (assuming that one or other variant is dominant and there is not some sort of averaging going on.)

    Is that what is happening?

    However, we would also expect the means to shift, would we not? If the higher IQ allele were dominant fewer women than men would have the lower IQ producing case, while if the lower IQ variant were dominant, more men than women would have the higher IQ producing case.

    • gcochran9 says:

      Deleterious mutations are usually recessive. An individual with one completely non-functional copy of a gene often doesn’t suffer much harm, even in cases where two nonfunctional copies of that same genes would be lethal. Which is not to say carriers of lethals are completely unaffected. On average, such heterozygotes suffer a 2% loss of fitness, at least in Drosophila.

      Deleterious recessives on the X chromosome will show up almost entirely in men. All else equal, you’d expect to see more mentally retarded men than women. And you do. Since the X chromosome is enriched for genes that influence intelligence, this is even more common than you might think

      • The fourth doorman of the apocalypse says:

        Jackson and Rushton claim that males have something like a 3.8 IQ point advantage over females on average.

        I need some pointers to material to help me understand the contribution to the variance of various alleles and in particular genes on the non-pseudo-autosomal portion of the X chromosome.

      • Jaim Jota says:

        If deleterious mutations on Y or X will kill a man but affect slightly a woman, then men are subject to harsher selective pressure than females and they must be also subject to a higher mutational rate. In THE Academy, Plato had written a paper concluding that men were more perfect than women and closer to the Idea (Form in the original). Now we know why.

  27. Jim says:

    Ronald – Who are the ten women you believe are among the top 1000 mathematicians of the 20th century? Also could you give your reasons for including them in such a list?

  28. namae nanka says:

    “In addition, it seems that testosterone is converted to estrogen in male brains, so women would seem to have had that switch operating as well.”

    not necessarily

    x inactivation

    • The fourth doorman of the apocalypse says:

      Thanks. I thought I had read somewhere that estrogen was largely blocked from entering the female brain during development but could not find it. Thanks for the other ref.

    • The fourth doorman of the apocalypse says:

      A quick check on Wikipedia suggests that only genes on the pseudoautosomal region of the X chromosome, escape silencing. This makes sense because since the Y chromosomes carry the same genes, there is no need for dosage compensation for them.

      I found this comment in the Migeon paper interesting:

      here are 15 genes that are unique to the Y, and those genes are usually expressed only in the testes. To date, no one has found the Y genes that confer mathematical superiority!

      Also, it seems to be saying “rah rah, women are great because they have so many benefits from mosaicism” but it fails to note that this also means that they are a reservoir for bad mutations among those 1,100 genes because they are essentially only eliminated among men.

  29. namae nanka says:

    “I found this comment in the Migeon paper interesting”

    It’s amazing how much the ‘gender-equality in maths’ industry keeps cropping up.
    A celebrated factoid from Hyde studies that went against the Larry Summers hypothesis was that there were more asian girls than boy scoring above 99th percentile in Minnesota. (at least reported so)
    See if you notice something funny in the table here:

    • misdreavus says:

      More BS from Janet Hyde. Of course, she had to cherry pick that single year, in a single state, for a single age cohort from the NAEP data where asian females slightly overperformed males above the statewide 99th percentile.

      n = 219, enough said about that. Statistical reasoning, how does it work?

      It is this sort of brazen dishonesty that simply infuriates me. These people simply cannot be reasoned with through facts or evidence — their ideological conclusions arrive before their analysis, and they will massage the data however they please, facts and decency be damned.

      There’s another paper where she emphasizes that female participation in the International Math Olympiad fluctuates wildly from country to country, even between nations with similar ethnic profiles. As the ever prescient Sharon Begley reports in Newsweek magazine:

      For anyone who still believes that innate factors explain the math gender gap, as I wrote last year, look at countries with a common gene pool. East Germany regularly sent many more girls than West Germany to the International Mathematics Olympiad by margins of 5-to-0; Slovakia sent more girls by a margin of 3-to-1; Korea topped Japan by 6 to 0. As I wrote then, “It’s hard to see that as anything but the result of the starkly different social and other environmental forces in each country, not intrinsic biology.”

      By the way, the discrepancies amount to a few female participants per decade out of a pool that usually exceeds several dozen. Need I mention that the same data says that Hong Kong’s percentage of girls dropped from 16.7% to 3.3% during a time period when women made immense strides in economic and social parity with men? The USSR’s percentage also dropped from 21.7% to 3.3% during the nineties, as did the the Republic of China, which has seen a continual decline in female participation from 15.8% to 5.6% to 1.7%. So is it sociocultural trends, or random chance? Must be all that patriarchy working tricks on everyone’s minds, once again.

      I don’t have the time to do the statistical analysis, and there are only three data points (at most) per nation in the table provided, but you probably wouldn’t find any stable long term trend over time.

      There’s a lot more bullshit where that came from — you can peruse through the paper at your own leisure through the link below. Happy turd hunting!

      • Anonymous says:

        why are gay men offended by the “Gay “germ” theory? And if the GG theory were proven, and a prevention found, would you predict that most gay men would be offended? If (hypothetically) a cure were found would most remain gay?

      • gcochran9 says:

        Unless I’m missing something, those numbers aren’t even possible.

      • The fourth doorman of the apocalypse says:

        Anon said:

        why are gay men offended by the “Gay “germ” theory? And if the GG theory were proven, and a prevention found, would you predict that most gay men would be offended? If (hypothetically) a cure were found would most remain gay?

        You have to distinguish between an organism that flips a developmental switch that cannot be unflipped vs an organism that manipulates gene expression to get its job done. (And we don’t know how the organism propagates itself. At least with Toxoplasma gondii we know what it’s lifecycle is.)

        Consider that males, at least according to Eleanor MacCoby, change from wanting to exist in almost exclusively all-male groups before puberty to wanting to be involved with females after puberty, …

        However, if it it turns out that the organism that produces male homosexuality can be identified and destroyed and that can “cure” homosexuals, I will enjoy watching heads explode all over the Western world. I would imagine that any such research would be suppressed and it would never attract funding.

      • The fourth doorman of the apocalypse says:

        Unless I’m missing something, those numbers aren’t even possible.

        Heh. 219 Asians. Assume something like 110 males and 109 females, although working from the 6.27% of males above the 95th percentile, I get closer to 112 males and 107 females, but the numbers do not work out correctly.

        So, then, how do you get 1.25% of the males getting above the 99th percentile? Or 1.37% of the females? If there were two females, that suggests that females were 73 of the 210, but then we would have 1.85 males scoring in the 99th percentile.

        As Greg says, those numbers look bogus. I am surprised that the reviewers did not catch that. Perhaps there are lower standards for female authors.

  30. Matt says:

    Back to the main topic,

    would we estimate this would affect regression to the mean within a Black population, such that there would less expected regression (under the same basis that the deleterious variants which Blacks hold, which amount to more load in total, are of small individual effect and large in number)?

    or have I got a confusion of ideas here?

  31. misdreavus says:

    If schizophrenic people had a powerful, international lobby warning the world that paranoid delusions were healthy and morally neutral — if telling schizophrenic people that the postman really _wasn’t_ plotting to murder them constituted “hate speech” — if religious loons routinely targeted schizophrenic people for special moral opprobrium — if they were unusually likely to be disowned by their closest relatives — if academia and intellectuals worldwide campaigned for the public acceptance of erratic, violent behavior — surely you would think schizophrenics would take umbrage at the mere assertion that something was wrong with their neutral circuitry?

    Either way, what’s the point now? You can’t unscramble an egg. The damage has been dealt.

    Hell I didn’t like it, either, but it’s probably true. I was even more offended by the possibility of hereditary differences in cognitive ability between different populations — but there’s even more evidence for that.

    I hate bullshitters, and I wish they would go away forever.

  32. namae nanka says:

    “n = 219, enough said about that. Statistical reasoning, how does it work? ”

    “As Greg says, those numbers look bogus. I am surprised that the reviewers did not catch that.”

    They are for 95th percentile.
    There was cherry-picking alright:
    “Minnesota was the only state for which actual gender ratios were quoted above the 99th percentile.”

    But what kinda cultural explanation goes for the fact that the M/F ratio was reversed in standard 11 using percentages(while the same is noted to be a statistical illusion creating SAT-M gender-gap), never mind the asian gender egalitarianism….

    • The fourth doorman of the apocalypse says:

      They are for 95th percentile.

      My mistake. Then it’s worse than I thought. Let’s assume that half of the Asian and PIs made it into the 99th percentile. So, about 50 males and 50 females, or something like that.

      Hmmmm, I have never seen a half and Asian although I have seen some halfies.

    • The fourth doorman of the apocalypse says:

      Trying to make the numbers agree against the 95th percentile quoted numbers also seems to make no sense. Based on the 5.71% female numbers it looks like there were 105 females in the group of 219 tested individuals, but then you get a fractional number of males, and moving to the next whole number of males makes the quoted percentages wrong.

      So, ignoring all issues of cherry picking and the question of drawing conclusions of the nature the authors did from an N of 219, the numbers just do not seem to work. Surely someone should have noticed that or were they all so breathlessly happy to be able to conclude “Asian girls are great?”

      • Brett says:

        The numbers are possible; I tried to work it out the same way as you until I had someone point out to me that the N=219 is very likely referring to the total number of Asian children above the 95th percentile. With that assumption, you can work out the numbers as:

        Total Asians: 3660, 1835 male 1820 female
        Asians above the 95th%: 219, 115 male, 104 female
        Asians above the 99th%: 48, 23 male, 25 female

        With these numbers, you get the results in the table precisely; no need for fractional children.

      • gcochran9 says:

        You must be correct.

  33. namae nanka says:

    some data here:

    it’s funny that since they have spent so many years saying that a small effect size didn’t matter much, now that they have female means greater than male means they can’t use it for girls are better at maths.

  34. Jaim Jota says:

    Dear Doorman, I encountered the same phenomenon in the Mexican agricultural census, that counted chickens to two decimals (say 2,000,000.15 chickens in the State of Guerrero). Therefore, it exists. Statistical data can be subjected to scale transformations and in the transformed scale, “the constant variance assumption is realized. Such transformations can also correct for departures of observations from normality because unequal variance can be related to the distribution of the variable. Massaging can bring data closer to normal distribution, to reduce relationship between mean and variance, to reduce the influence of outliers, to improve linearity in regression, to reduce interaction effects, to reduce skewness and kurtosis.” Quoting Theodor Herzl, “It is not a dream if you want it”.

  35. namae nanka says:

    “Based on the 5.71% female numbers it looks like there were 105 females in the group of 219 tested individuals”

    5.71% of asian girls made it to the 95th percentile overall, the over-representation of asians(and whites) due to the lack of NAMs in the top 5%.

    “N=219 is very likely referring to the total number of Asian children above the 95th percentile. ”
    “With these numbers, you get the results in the table precisely; no need for fractional children.”

    However N = 62,526

    The Minnesota numbers for Asians are worse than white(boys) in the Hyde study, looking up the NAEP and the state assessment results, asians/PI in Minnesota underperform whites and are way lower in attaining higher levels than their national average in NAEP, and vice-versa for whites.

    Reading and Math proficiency of Minnesota students – 2012 assessment results

    • American Indian: Math 38.5%, reading 55.9%
    • Asian: Math 59.4%, reading67.3%
    • Black: Math 32.6%, reading 52.7%
    • Hispanic: Math 38.2%, reading 53.9%
    • White: Math 68.4%, Reading 81.9%

    • The fourth doorman of the apocalypse says:

      Is it normal to say N=219 when that is the number in the 95th percentile and you also have the 99th percentile as well?

      Anyway, issue resolved.

  36. namae nanka says:

    “Total Asians: 3660, 1835 male 1820 female
    Asians above the 95th%: 219, 115 male, 104 female
    Asians above the 99th%: 48, 23 male, 25 female”

    for the coda, the underperformance of asians is Minnesota is explained by the fact that:

    “Minnesota’s Asian Pacific population is vastly different from the national make-up. 50.2% of our
    population identifies as Southeast Asian vs. 20.7% of the national average”.

    Hmongs(who?) are the largest asian group.
    Divvy up the remaining half(and the 95th percentilers) of better-performing asians into chinese, indians, japanese, koreans(and perhaps a few nyugens) and you have entered the realm of statistical nonsense.

  37. The fourth doorman of the apocalypse says:

    It seems widely reported that low IQ blacks have no problems with language but that low IQ whites have problems with language.

    Does that suggest anything?

    • gcochran9 says:

      Then you could give an example of such a report.

      • The fourth doorman of the apocalypse says:

        I should learn not to make un-researched remarks.

        The best I could find is brought to us by Google and Arthur Jensen via Flawless Logic or somesuch:

        Surprisingly, blacks tend to perform relatively better on the more culture-loaded or verbal kinds of tests than on the culture-fair type. For example, on the widely used Wechsler Intelligence Scale, comprised of 11 different subtests, blacks do better on the culture-loaded subtests of vocabulary, general information, and verbal comprehension than on the nonverbal performance tests such as the block designs. Just the opposite is true for such minorities as Orientals, Mexican-Americans, Indians, and Puerto Ricans. It can hardly be claimed that culture-fair tests have a built-in bias in favor of white, Anglo, middle-class Americans when Arctic Eskimos taking the same tests perform on a par with white, middle-class norms. My assistants and I have tested large numbers of Chinese children who score well above white norms on such tests, despite being recent immigrants from Hong Kong and Formosa, knowing little or no English, and having parents who hold low-level socioeconomic occupations. If the tests have a bias toward the white, Anglo, middle-class, one might well wonder why Oriental children should outscore the white Anglos on whom the tests were originally standardized. Our tests of Mexican-Americans produced similar results. They do rather poorly on the culture-loaded types of tests based on verbal skills and knowledge, but they do better on the culture-fair tests. The same holds true for American Indians. All these minorities perform on the two types of tests much as one might expect from the culture-bias hypothesis. Only blacks, among the minorities we have tested, score in just the opposite manner.

        This, however, is not quite what I was thinking of, and may simply have remembered the arguments of those who wish that IQ was not a useful construct.

  38. RT says:

    Perhaps at least part of the narrower black variance is explained by non-representative samples. Rushton and Jensen (2009) asserted that a lot of norming studies don’t include the poorest blacks from intercity or rural Southern areas and that the actual B-W IQ gap in the US may be something like 1.5 d (white d that is) instead of 1 or 1.2 d. I believe Murray may have said something similar. If this is correct, wouldn’t such truncated samples understate the true black IQ variance?

  39. rob says:

    If all human populations use XY/XX sex determination(they do), and the mutation rate is higher in blacks than whites, we would expect to see sex ratio differences. Specifically, the m:f ratio at birth should be lower in the higher mutation population as X chromosome defects weed out males. It shouldn’t be a huge effect since only a few percent of genes are X-chromosomal.

    The wikipedia human sex ratio page says the white ratio is 1.05 for whites and 1.03 for blacks in the US, with similar numbers for European and African countries. Not proof, but certainly consistent with Cochran’s theory.

    • gcochran9 says:

      I’m not saying that blacks have a higher mutation rate than whites: I’m saying that populations with high average paternal age have higher-than-average mutation rates. When that population changes its ways, stops having especially old fathers, mutation rate returns to normal. Unfortunate; if they had high paternal age for a long time, they built up increased genetic load that takes a long time to go away.

      Would you expect to see a different sex ratio in a population with an unusually high genetic load? Deleterious mutations on the X chromosome would mainly do their bad shit in men: it could be so.

      • rob says:

        Sorry, had a higher mutation rate. If I remember right, the sex ratio is lower (more girls) for older fathers, that’s despite boys not receiving paternal X chromosomes with ostensibly more de novo mutations. I wonder if daughters of older fathers have fewer boys than the sons.

        The X chromosome should purge load faster than autosomal chromosomes because each individual defect has a low frequency, and p^2 << p for small p, but that's true for all populations. Can we compare X chromosomal:autosomal defect rates in different populations? If American black people have had lower paternal age than black people in Africa for a while, we'd expect black people in the US to have lower rates of X chromosome defects: autosomal defects than African blacks because purifying selection lags on the autosomes.

  40. That Guy says:

    I think what a lot of people are dancing around here is that there are 2 groups with narrower distribution of IQ:
    1. Blacks – relative to Whites/Asians
    2. Females – relative to Males

    I think some of the B/W difference can be explained by the observation that Male Blacks seem to have a less masculinized brain (or more feminized?!) than Male Whites/Asians. The question is why?

    I think the cognitive profile (Math, Verbal, Spatial) of Male Blacks is more similar to Female Whites/Asians then to Male Whites/Asians – am I correct?

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