Breeding Value

I’m going to steal most of this example, to make a point. The numbers are chosen  for convenience.

Measured IQ can be decomposed into two components – genotypic expectation and everything else, which means epistasis,  developmental noise, measurement error, environmental influences, etc. We don’t know much about this second component.

Imagine that the narrow-sense heritability of IQ  is 0.64 – which means that 64% of the variance  in IQ scores can be explained by differences in genotypic expectation, 36% by the second, grab-bag component.

Imagine someone with a +4 SD IQ score (160).   On average, that person will have a higher than average value for both genetic and grab-bag components: +3.2 SD for genotypic expectation and +2.4 SD in the miscellaneous component.

Suppose that two people like this marry (a most unusual pairing).  Their kids will have an genotypic expectation of +3.2 SD and an average of +0.0 “miscellaneous”, for an IQ averaging +2.56  SD. If two people with that kind of ancestry married,  their kids, the next generation, would also have an average IQ of 2.56 SD.

They’re different from the typical kid with an IQ of +2.56 SD.  His genotypic expectation will be +2.048 SD, while he’ll have +1.536 SD in the misc component. In other words, with the the typical kid with an IQ of +2.56, a lot of it is luck.  Marry two like this and their kids will regress towards the mean (down to +1.6384 SD).

Families will vary.  Some parents have high genotypic expectations and hardly any luck: their kids won’t regress much.  Others, whose high IQs depended a lot on luck, will have kids that regress a lot.

By looking at the IQ values of close relatives, one can estimate the genotypic expectation component – the “breeding value”.  It may also be possible to estimate this by a Visscher-type method, looking at overall genetic similarity with a large set of distant relatives.

In other words, we should be able to estimate the extent to which a high IQ will breed true, particularly easily in large families, but maybe for everybody.

The estimated breeding value is what you want to consider when looking at sperm or egg donors. Or, if you’re into that sort of thing, even in an online dating or matchmaking  service.

The ag majors know all this, but anyone majoring in any other discipline is most unlikely to.  I don’t think that the average young genomicist knows it.

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113 Responses to Breeding Value

  1. dearieme says:

    “anyone majoring in any other discipline is most unlikely to.” Vets? They tend to be cleverer than Ag majors too, so it may matter to them in a personal way.

  2. Genobollocks says:

    You’re too old to be this ignorant of the long history of this idea. Yes, shared family variation is traditionally low, but what about prenatal env. variance, nutrition, drugs and the like? They wouldn’t confound this at all? What about gene-environment-assocations, e.g. rich parents send their slightly-above-average kids to good colleges?
    Of course heritability is intended to predict breeding value, and yes, if you got really good narrow-sense heritability (and yes, some of Visscher’s paradigms might be an improvement here), you could predict breeding value for sperm donors. JS Lee did this for sperm donor kids, and found the expected results for height: It’s too early to say for education.

    But no, with twin study heritability estimates in natural families, you can’t do marker-assisted prediction or selection. Ag majors may not know this, because they have it easy. FWIW JS Lee is not an ag major.
    Have you forgotten about the Scottish Mental Survey? Do you think intelligence researchers have? Twin study heritability failed to predict lower intelligence in the next generations based on fertility and all the post-hoc justifications for that failure by the contemporaries and e.g. Lynn are motivated reasoning. They may turn out to be right in the end, but parsimony left the room a while back.

    • JayMan says:


      “They wouldn’t confound this at all? What about gene-environment-assocations, e.g. rich parents send their slightly-above-average kids to good colleges?”

      Meng Hu has a good post up showing why (at least in today’s developed world), gene-environment correlations are unlikely to matter much.

      The Genetics of Intelligence « Meng Hu’s Blog

      • Genobollocks says:

        It does not have to matter much. I’m not arguing that heritability is zero, reducible to GxE or even low at all.
        Just that Cochran’s proposed breeding value prediction, even marker-assisted prediction, would not be useful, as has been shown time and again.
        Yes, it might work in sperm & egg donor cases, as the JS Lee study shows, but seriously, I doubt Christian Cochran cares.
        It’s motivated reasoning, trying to fantasise reasons into existence, why those damn people just refuse to turn dumber over time.

      • gcochran9 says:

        You know, I have no idea what my motive here is supposed to be. Why don’t you tell me, before I ban you?

  3. JayMan says:

    “By looking at the IQ values of close relatives, one can estimate the genotypic expectation component – the “breeding value”. It may also be possible to estimate this by a Visscher-type method, looking at overall genetic similarity with a large set of distant relatives.”

    Indeed. It’s my understanding that regression to the “mean” is based on having no knowledge of the family. So in our case, I used (my estimated) IQs for our parents, and took the mean of that to guesstimate the regressed average IQ of my wife’s and I’s children. It comes out to be near 130, which isn’t bad. ;)

  4. j3morecharacters says:

    When you purchase dairy breeding material, it comes with extensive documentation of milk yields of daughters, granddaughters, and the bull’s whole mishpoche. Heredibility is calculated. Paradoxically, no one applies this knowledge in their personal reproductive lives. Once, marriages were annuled when a defective uncle or a suicide was discovered. Our times are profoundly against these things.

    • JayMan says:


      They think they can compensate with “nurture”. ;)

    • JayMan says:

      Though strictly, I wouldn’t say that this thinking is completely abandoned. There’s a great deal of assortative mating going on. This is pretty much what you’d get if people took full family history into account.

      • Jason says:

        There are also more migration, cosmopolitanism, economic constraints, government enforced anti-discrimination laws, etc., that militate against assortative mating today.

      • j3morecharacters says:

        Jason, I dont think the factors you mentioned are relevant at all. There are no government enforced anti-discrimination laws – not in the USA nor anywhere else. Economic constraits – humnaity was never so wealthy a today, so there are almost no real economic constraits to assortive mating. Migration always existed and if you think about it, it should promote assortive mating, Regarding cosmopolitanism, there was never a more cosmopolitan, universalist ideology than the Catholic Church and it exists now two thousand years. Before them, Greek and Roman paganisms were fairly universalists too. What we have today is an humanity totally disengaged from nature, from agriculture and animal husbandry. living in a TV phantasy world.

      • j3morecharacters says:

        Regarding anti-discrimination laws that you say forbid assortative mating, I imagine that Major Di Blasio intended to marry a tall blond German-American like himself but the laws you mention forced him to marry a short African American lesbian.

      • Jason says:


        Of course they’re relevant. There are government enforced anti-discrimination laws today. There are economic constraints today that make fleeing diversity more difficult than it was in the past. You need to be wealthier today to flee diversity. There is a lot more migration today. You yourself have lived in what, 3 continents in your lifetime?

      • Jason says:


        Anti-discrimination laws prohibit people from creating certain social environments that facilitate certain kinds of assortative mating.

        Think about your own country. The law of return discriminates in favor of Jews and helps establish a Jewish social environment that obviously facilitates mating among Jews.

  5. Kabal says:

    Wouldn’t the average “miscellaneous” be non-trivially greater than 0.0 for +4.0 STD parents, since we would expect a positive correlation between parental IQ and children’s envrionmental influences? So the intergenerational drop wouldn’t be as large as 4 STDs to 2.56.

    Either way, regression to the mean is a bitch. I’m extra careful not to knock up any Dominican or South East Asian girls for this reason. I’ll play things a little looser with American white girls from smart families.

  6. JayMan says:


    “Wouldn’t the average “miscellaneous” be non-trivially greater than 0.0 for +4.0 STD parents, since we would expect a positive correlation between parental IQ and children’s envrionmental influences?”

    The “environment” you’re thinking is not the “environment” he’s talking about.

    See here:

    it’s not nature and nurture… | hbd* chick

    • Kabal says:

      The environmental influences I’m thinking of is the one Cochran’s talking about, a sub-component of the residual after accounting for genotype, the residual being “everything else”/”miscellaneous”–“which means epistasis, developmental noise, measurement error, environmental influences, etc.”

      If there is a positive correlation between genotype and environmental influences, and if the rest of the non-environmental influences “miscellaneous” grab-bag is random noise with respect to genotype, then that should push the whole “miscellaneous” component into positive correlation territory.

      • JayMan says:

        Except that there isn’t much evidence that gene-environment correlations have much of an effect, which is the crux of your point.

  7. bob sykes says:

    Correct my (mis)understanding. Isn’t the original genetic component 2.56 SD (.64 x 4) and the original grab bag component 1.44 SD (.36 x 40)?

    • Anonymous says:

      No. A narrow-sense heritability of .64 comes from the square of the correlation coefficient of .8, and the .36 fraction corresponds to a value of .6 in the same way. Equally important, the 3.2 SDs in the genotypic component and the 2.4 in the miscellaneous component shouldn’t add up to 4 SDs, because the SDs for these things aren’t as big as the 15-point SD for measured IQ.

  8. Patrick Boyle says:

    My first reaction was – has there ever been a marriage between two person both of whom were at 4 SDs above the mean in IQ? Standard IQ tests like the WAIS only measure up to 160. So that IQ is the at the ‘end of the world’. The lay public blithely speaks of higher IQs, but an IQ above 160 isn’t really meaningful.

    Also standard z-score tables seldom go above 3 SDs. There are a few published that go up to 3.4 but I couldn’t find any that went to 4. The normal curve that far out is asymptotic.

    There are some guys that smart – you may be one of them – but almost no women because of their lower variability. Since independent probabilities multiply it seems likely to me that never in the history of man on Earth have two such people wed.

    I’m not real confident in this conclusion. There may be ‘fat tails’ in operation. But if there have ever been two people that smart who bumped into one another it can’t have happened often. So it seems an odd choice for an example.

    • Brett says:

      What on Earth makes you think the probabilities of a husband and wife having high IQ are independent?

      • gcochran9 says:

        There is some assortative mating for IQ, but it’s fair to say that cases where both parents have an IQ of 160 or higher must be very rare.

      • Brett says:

        True enough, they’re going to be rare, but I doubt they’re non-existent. I’m thinking particularly of undergraduate classes at Caltech. I know personally several 145-145 IQ couples that came out of there. I don’t know for a fact any 160-160 pairings, but I’d guess that there are at least a couple men of that calibre in each class and probably a woman of that calibre every few years or so. Given the 40 or so years since women have been attending, I wouldn’t be surprised to find such very high IQ couples.

      • Anonymous says:

        There are girls at Caltech?

      • Anonymous says:

        It’s 37% girls, believe it or not.

      • Harold says:

        I doubt either of them are +4 SD in IQ, but Dana Moshkovitz and Scott Aaronson have a daughter together. Both are Ashkenazi computational complexity theorists in the department of Electrical Engineering and Computer Science at MIT, and thus possibly both +4 SD on some dimension of cognitive function.

        Incidentally, I see that Scott has West Hunter in his blogroll, which suprises me given that he has said some silly things which a reader of this blog ought to have known better than to have said (and I’m not even referring to when he implied that Turing machines were better than the lambda calculus).

      • Richard Sharpe says:

        I am told that young women say that at Caltech the odds are good, but the goods are odd.

      • Anonymous says:

        I’m very curious as to the degree to which the admissions process is rigged in order to increase the number of girls. There are very few girls who have the cognitive abilities required to succeed at Caltech and a desire to major in STEM.

      • gcochran9 says:

        I don’t think it’s that much of a secret:

        “This year, however, Caltech began a new admissions policy that promises to ease the glomming problem and, more seriously, to tap a new reservoir of brainpower
        for the nation’s technological needs. The school offered enrollment to all female applicants meeting basic entrance requirements, even if that meant rejecting equally qualified males.

        It is too early to tell how well the social and career goals of the change will turn out,

        administrators say. But they are encouraged. After all, the percentage of women in Caltech’s freshman class increased from 17% last year to 30% this fall.
        That means 66 out of the current 215 freshman class are females while 338 of Caltech’s 1,821 undergraduate and graduate students are women.”

  9. Patrick Boyle says:

    I think Galton did us all a disservice when he coined the phrase ‘Nature vs. Nurture’. The main problem – which you alluded to – is that Nurture in this cast of the issue gets credited with the residual or unexplained variance. The concept of Nurture only seems important because we dump the error term into it.

    Nurture is really made up of all the many proposed independent variables. They should be considered one by one. For example the National Merit people did a study decades ago to try to determine how important the quality of teaching was to achievement. They used their humongous data store to try to gauge how much more students learned at Harvard than they did at any old Podunk U. Everyone knows that Harvard hires the most eminent faculty – right?

    But this environmental variable – better teachers – couldn’t account for any of the achievement variance. None. All the variance they could measure was in the students. None was in the faculty or facilities. Harvard has smarter graduating seniors only because they selected for smarter matriculating freshmen. Learning English from a Pulitzer Prize winner or Chemistry from a Nobel Prize winner didn’t seem to matter.

    More recently, parents all over America tried another environmental manipulation on their kids. They played Mozart to them in the cradle. We know now that Mozart in the kiddie’s bedroom has no measurable effect. We also know that IQ is about 70% heritable. But we misinterpret that finding to conclude that the environment – whatever the hell that means – is responsible for the remaining 30%.

    That’s not what it means. In fact in practical terms it means that the only thing that matters is heredity. All the rest of the variance is error or effects so small that they don’t matter. But instead we get financially interested groups like teacher’s unions, use that 30% figure to justify governmental subsidies for advanced teacher’s education, higher pay rates and nicer classrooms.

    • ursiform says:

      Being a Pulitzer or Nobel Prize winner doesn’t necessarily make one a good teacher. Top universities such as Harvard, and even many lesser universities, don’t choose their facility based on teaching skills. There would probably be some positive value in spending four years in classrooms with good teachers. Does anyone know of such a college?

      • j3morecharacters says:

        You know a good teacher by how far his students go. Henry Kissinger and Stanley Fischer had many successful students. Yet, was it their exceptional teaching skills or they had students with exceptional potential? I think it is some kind of “assortive mating”.

      • Harold says:

        Surely, having a good thesis advisor matters. Rather a lot I would think.

        Jaim asks, “was it their exceptional teaching skills or they had students with exceptional potential?” Of course exceptional professors get exceptional students at the doctoral level, and such Professors are surely a great resource for their students whether they are great teachers or mediocre, simply by being a fount of knowledge, easily grasping what the student is working on and directing the student down fruitful avenues of inquiry (which comes from intelligence rather than any independent teaching ability). Here I am thinking more Alonzo Church and Stephen Kleene rather than Kissinger and his students.

    • dave chamberlin says:

      “We know that IQ is about 70% heritable,” fine so far. “But we misinterpret that finding to conclude that the environment -whatever the hell that means- is responsible for the the remaining 30%.” don’t forget that environment includes some children with an optimum combination of their parents genes for high IQ and some with a lousy combination. “That’s not what it means. In fact in practical terms it means the only thing that matters is heredity. All the rest of the variance is error or effects so small they don’t matter.” I beg to differ. Mr genius marries Mrs genius, well each of them were lucky winners of an ideal combination of genes that gave them genius. Will their children be so lucky? Probably not, regression to the mean, meaning regression to average luck rather than good luck. Mr and Mrs Genius will give their little ones every opportunity so that the big bad environment won’t chip away their spectacular IQ’s. Luck will, the roll of the DNA dice.

  10. Brett says:

    I’m not sure I’m following the numbers. The probability distribution for the additive genetic contribution in the general population is a Gaussian with a variance h^2. If we sample a person from this population with an IQ of V (measured in S.D.), we can update our distribution for this particular person’s estimated additive genetic contribution to a new Gaussian with a mean of V h^2 and a narrower variance h^2 (1 – h^2).

    So with a person of IQ 160 (4 S.D.), we would estimate their genetic contribution to have a mean of 2.56 and a narrower variance of 0.23.

    Ah, now I see. But that 2.56 is measured in S.D. units distribution of intelligence as a whole. The distribution of genetic contributions in the whole population has a narrower S.D. of h, so if we normalize to that, then this person has an estimated genetic potential V h^2 / h, or +3.2 S.D. Similarly, their grab bag contribution will be V (1-h^2) = 1.44 in S.D. units of total intelligence, but V sqrt(1 – h^2) = 2.4 in S.D. units of grab-bag contributions to intelligence.

  11. Greying Wanderer says:

    Won’t selecting on one single trait automatically be negative for everything else? That’s okay if you only want one thing e.g. milk yield or racing speed but in humans?

    Doesn’t it make more sense long-term to select against overall genetic load instead which to me implies selecting on a combination of looks, health, brawn and brains. If IQ is mostly a product of lots of genes of small-effect then doing that over time would create a population with high average IQ anyway – as long as they had all the necessary small-effect genes in the first place?

  12. Would average(parents IQ)/2 + average(grandparents IQ)/2 be a reasonable simplification of the genetic IQ component detailed here?

    It’s interesting reading this alongside some of Zig Englemann’s work, who maintains that the nuture component can be varied far more than is commonly achieved by non-standard approaches. The ideas aren’t mutually exclusive, but represent quite different perspectives on the same question.

    Another little gem I came across recently was an isonoetic (lines of equal intelligence) chart of Tasmania in the early 1950’s. The author of the paper(see, Peter Scott, found that there was strong correlation between the productivity of farms (specifically, not the fertility of the ground but the productivity of the farms) and the intelligence of the children across the state.

    • ursiform says:

      Some negative environmental conditions can inhibit brain development and have a seriously detrimental effect on intelligence. Pre- and postnatal malnutrition is one example. The situation where basic needs aren’t met is different than the case where they are and you are looking at the effect of other environmental factors and whether they can improve intelligence over the case where basic needs are met.

      • Yes, that is referenced in Englemann’s work – cases where (young children’s) environmental conditions have results in 30+ point drops in IQ over the test group. Also noted are historical and recent cases of specific training substantially increasing IQ (again, in the 30+ point bracket). Like so many things in the past, it’s just not the way education is approached these days.

      • gcochran9 says:

        Oddly enough, it doesn’t look as if it actually works.

        What a surprise!

      • ursiform says:

        I’m skeptical. If a runner with average speed gets run over by a truck it may significantly slow him down. But getting a good coach is unlikely to lead to a similar improvement toward the upside.

        If a child with the genes to develop a good brain is starved before or after birth he may develop a substandard brain. But it’s hard to see how any positive influence could lead to a similar improvement toward the upside.

        Environment can have a hugely negative effect–up to and including death–but is more limited in what it can do on the upside.

      • JayMan says:


        Pretty much. Very well put.

      • ursiform says:

        Note: Greg posted while I was writing my last post. I was responding to intuitivereason’s post.

      • Skepticism is good. I’ve got no personal data on the outcomes. The results of the broad 1970’s studies seem conclusive that the methodology worked better than anything else tested, and we are seeing the same sorts of improvement in the trial schools that are being run for some of the Australian aboriginal communities currently.

      • gcochran9 says:

        I’m looking at a summary of a number of evaluations of Direct Instruction that were somewhat rigorous. Here’s what they say:
        “Issues to Consider

        This program received a “promising” rating. Many of the evaluations of Direct Instruction were experimental in design, and those that were quasi-experimental used reasonably convincing comparison groups. The results varied significantly from study to study, with ten of the studies reporting mixed results, six reporting no significant differences between groups, and four reporting solely positive and significant differences for DI students. This lack of consistency among studies suggests that the overall evidence of DI effectiveness is limited. However, when results are considered across all studies, the majority of the evaluations reported at least some significant benefit accruing to students who participated in the Direct Instruction program. These benefits were found on standardized tests of general cognitive skills, reading, and mathematics, and on high school graduation rates.

        A pattern to note is that more-recent studies of the DI program, conducted in the 1990s and later, were less likely to report significant, positive program effects for students participating in Direct Instruction. It is unclear whether this is an artifact of study methodology, more-effective comparison group programs, changes in student learning patterns, or something else.

        Two studies assessed the Direct Instruction program in special-education settings, and neither reported significant findings favoring DI. Furthermore, on one measure in the study by Cole, Dale, and Mills (1991), Mediated Learning students significantly outscored DI students.

        Additionally, two studies assessed the effects of DI on juvenile and young-adult crime and arrest rates, and DI was not shown to be effective at reducing or preventing juvenile delinquency. ”

        10 mixed studies, 6 no difference, 4 clearly positive. Weaker positive signals with time. I wouldn’t put much stock in it, considering positive publication bias and wishful thinking. Of courser I’m biased by reading about zillions of other education approaches that made similar optimistic claims and are now sleeping with the Pharaohs.

        Pretty much every big city in the US with lots of minorities (and I’m not talking about Parsees, here) has some kind of cheating scandal (by the school authorities), in a desperate attempt to boost scores for NCLB. If anyone knew how to produce real, substantial improvements, why don’t they just do it?

        Which is not to say that all approaches have been exhausted. I was familiar with a certain University high school that had lost something like 90 basketball games in a row. Once, when they were by some miracle in the lead, an extremely attractive young lady in the stands shouted “If you guys win, you can have me!”

        They won.

      • Yes. There seems to be some variability in the results, and teachers unions hate it as the program can be conducted by people with minimal training in teaching. I would characterise DI as (primarily) a methodology for teaching under-performing students to perform tasks that they would otherwise find difficult to learn, by breaking them down into their simplest components and ensuring that each component task is learnt before proceeding further. It’s probably why it is working quite well up in North Queensland as they a) find it difficult to staff the remote Aboriginal schools, and b) the average performance is characteristic of the genetics.

      • gcochran9 says:

        I’ve been thinking that there might be a way for the Aboriginals to make a great contribution to the world.

      • Well.. they certainly have distinctively different genetic advantages.

      • The fourth doorman of the apocalypse says:

        Well.. they certainly have distinctively different genetic advantages.

        Can you elaborate on those advantages?

        Is it that they are more adapted to the Australian environment prior to colonization? Lower tolerance for alcohol? Lower cultural complexity resulting in greater ability to survive after a world-wide nuclear war? More Denisovan genes?

        You must have some in mind.

      • melendwyr says:

        Aboriginal advantages? To the best of my knowledge, the native peoples of Australia demonstrate a markedly better-than-Western spatial sense, which can plausibly be attributed to having to navigate through the outback without compasses or GPS for generation after generation. (Their map-making technologies are fascinating, BTW – the combination of mnemonic techniques and abstracted artifacts look more like modern art to the naive observer.)

      • gcochran9 says:

        They have very good visual acuity, as well. But I’m thinking of the good things that would happen if they all emigrated to the United States.

      • Richard Sharpe says:

        They have very good visual acuity

        But then the Chinese have been successful without such good visual acuity. (Or, at least, some of them have had remarkable reproductive success.) What’s up with that?

      • The fourth doorman of the apocalypse says:

        (Their map-making technologies are fascinating, BTW – the combination of mnemonic techniques and abstracted artifacts look more like modern art to the naive observer.)

        And yet the Italians invented real technology for navigating the oceans of the world that also looks a bit like art and certainly looks more like technology.

  13. Steve Sailer says:

    There are famous examples of assortative mating upon intelligence among Darwin’s ancestors and descendants: look up names like Keynes, Vaughn Williams, Wedgewood, and Benn.

  14. Steve Sailer says:

    Also, look up Huxleys and Arnolds, such as Nobel laureate Arnold Huxley, who was the third most famous son in his own family.

  15. Anonymous says:

    I would love to see Visscher and colleagues do a sibling similarity study of IQ, as they have done for height and BMI. It could put to rest the heritability question once and for all.

    • steve says:

      Genome-wide association studies establish that human intelligence is highly heritable and polygenic

      General intelligence is an important human quantitative trait that accounts for much of the variation in diverse cognitive abilities. Individual differences in intelligence are strongly associated with many important life outcomes, including educational and occupational attainments, income, health and lifespan. Data from twin and family studies are consistent with a high heritability of intelligence, but this inference has been controversial. We conducted a genome-wide analysis of 3511 unrelated adults with data on 549 692 single nucleotide polymorphisms (SNPs) and detailed phenotypes on cognitive traits. We estimate that 40% of the variation in crystallized-type intelligence and 51% of the variation in fluid-type intelligence between individuals is accounted for by linkage disequilibrium between genotyped common SNP markers and unknown causal variants. These estimates provide lower bounds for the narrow-sense heritability of the traits. We partitioned genetic variation on individual chromosomes and found that, on average, longer chromosomes explain more variation. Finally, using just SNP data we predicted ~1% of the variance of crystallized and fluid cognitive phenotypes in an independent sample (P=0.009 and 0.028, respectively). Our results unequivocally confirm that a substantial proportion of individual differences in human intelligence is due to genetic variation, and are consistent with many genes of small effects underlying the additive genetic influences on intelligence.

      • Even better: DNA Evidence for Strong Genome-Wide Pleiotropy of Cognitive and Learning Abilities (

        That is, intelligence is mostly general at the genetic level even. I couldn’t think of a greater stake in the heart of the ‘multiple intelligences’ theory.

        (Reading the paper again though I’m unable to see why they tested ‘g’ vs language and ‘g’ vs mathematics instead of language vs mathematics. Showing the latter would sound even more impressive to me. Anyone able to explain?)


        Very different neurocognitive processes appear to be involved in cognitive abilities such as verbal and non-verbal ability as compared to learning abilities taught in schools such as reading and mathematics. However, twin studies that compare similarity for monozygotic and dizygotic twins suggest that the same genes are largely responsible for genetic influence on these diverse aspects of cognitive function. It is now possible to test this evidence for strong pleiotropy using DNA alone from samples of unrelated individuals. Here we used this new method with 1.7 million DNA markers for a sample of 2,500 unrelated children at age 12 to investigate for the first time the extent of pleiotropy between general cognitive ability (aka intelligence) and learning abilities (reading, mathematics and language skills). We also compared these DNA results to results from twin analyses using the same sample and measures. The DNA-based method revealed strong genome-wide pleiotropy: Genetic correlations were greater than 0.70 between general cognitive ability and language, reading, and mathematics, results that were highly similar to twin study estimates of genetic correlations. These results indicate that genes related to diverse neurocognitive processes have general rather than specific effects.

      • Anonymous says:

        I’ve seen both of these studies before, though I don’t recall reading either of them. Regardless, they’re both based around looking at genetic similarity between unrelated individuals. The problem with this method is that genetic differences are confounded with environmental differences. For instance, in the US, having genetic variants common in sub-Saharan Africa correlates with being poorer than average and a below average IQ. Thus poverty could be entirely responsible for low black IQ (not my position, just making a point) and one would still find that people who shared genetic markers for African ancestry were more alike in IQ than would be expected by chance.

        Visscher’s method is to compare the genetic similarity of full siblings to their phenotypic similarity. Since siblings don’t share exactly 50% of their genome, those that are more alike genetically should be more alike phenotypically assuming narrow sense heritability is non-zero. The degree to which the genotypic similarity predicts phenotypic similarity allows for precise estimates of narrow sense heritability totally free of any confounding factors.

  16. BB753 says:

    Yao Ming, the tallest Chinese BB player, was bred by the Chinese authorities, so to speak, by encouraging the marriage of his tall BB player parents. Or so the story goes.
    The People´s Republic might have been doing similar human experiments with high IQ couples. Who knows?

  17. Jim says:

    The cheating scandals publicly reported as well as the UNC scandal are probably only the tip of the iceberg.

  18. j3morecharacters says:

    Say we accept as truth that 70% of human capabilities are inherited and the rest is chance (not environment). In that world, the worth of education for those who cannot learn would tend to zero. In such a world (and I believe we do live in such a world) how could humanity organize itself in a more efficient, rational way?

  19. j3morecharacters says:

    P.S.: I’m not discarding the possibility that American democracy, that has created such an abundance of wealth and scientific advance, is such a system.

  20. kai says:

    Easy: sexually attractive == low genetic load. My guess is that any species that is sexually selective is also quite good at estimating genetic load. When the species is not, then the sorting is done by high early mortality, or by competition and harem building.

  21. panjoomby says:

    exactly: when environment matters it is usually negative – traumatic brain injury, etc.

    “good” teaching (breaking things down into steps, etc.) spreads the distribution out even more, b/c higher ability folks benefit more from good teaching than lower ability folks. good teaching creates wider gaps (“gasp”)

    • Ja, I think I heard this referred to as the “iron law of psychometrics” once, but couldn’t find the paper. Any takers?

      This is a principle most people would accept for any other skill than IQ; if you sent children to music and dance academies from age 6-18 those with innate talent would become really good, while us nerds would still not be able to carry a tune nor follow along with the rhythm even after thirteen years of instruction.

      • melendwyr says:

        Is there any empirical basis for the idea that ‘nerds’ lack rhythm and musical skill? My entire family is nerdy, and they’re all quite musical. Rather a lot of famous physicists also had musical interests, although not necessarily the talent and time to become truly good. Feynmann had his bongos, Einstein his violin (but was supposedly terrible). Mozart might have been a brilliant mathematician if he hadn’t been encouraged to go into music.

        I do find myself wondering what’s responsible for specific affiinities and talents, if the mechanism behind high IQ is general; anecdotes and experience strongly argue that Could there be two different phenomena involved, and truly brilliant people have both generally efficient brains and neural architecture that’s focused in certain areas?

      • melendwyr says:

        Drat. Let’s try that again:

        [...] anecdotes and experience strongly argue that there are loose types of mental skill, even if the “multiple intelligences” thing is nonsense.

      • Endre Bakken Stovner says:

        No, there is none that I know of, it was just an example based on a stupid stereotype. The opposite is likely to be the case:

        Deary, 94: “However, there is a growing body of evidence that supports a competing hypothesis, viz. that the auditory processing-ability—intelligence association is explained by the fact that individuals with higher ability scores have superior pitch discrimination ability… A well-fitting structural equation model suggested that information- processing speed and pitch discrimination ability were both significantly associated with nonverbal and verbal IQs, and that speed was the more important factor.”

        Ruthsatz, 08: “Higher-level musicians report significantly higher mean levels on innate characteristics such as general intelligence and music audiation…”

        The point about how music school would increase the difference in skill levels between people with and without musical ability is still good though.

      • melendwyr says:

        So there are no distinctions between verbal/mathematical and spatial ability, now? When did this occur?

      • Endre Bakken Stovner says:

        My first answer was to the question whether nerds were less musical.

        “[could there] be two different phenomena involved, and truly brilliant people have both generally efficient brains and neural architecture that’s focused in certain areas”.

        You are right, abilities are modular (obvious because of idiot savants and those with localized brain damage.) But this doesn’t mean that intelligence isn’t mostly general, which is what some (most notably Gardner) has argued. This is because the efficiency of these modules is highly correlated. The reason is likely that these abilities are all to some degree affected by brain characteristics such as chemical neurotransmitters, neural conduction velocity, amount of dendritic branching, degree of myelination of axons, number of neurons etc.

        Jensen used an analogy to explain this (p. 131, The g factor), similar to mine below:

        Imagine people as factories, and modules (verbal, spatial, musical, mathematical etc.) as machines. Each factory has the same types of machine, but they differ in their capacity between factories. However, each factory has a gear chain that drives the five machines, and each gear chain moves in a constant, but different speed in each factory. Factor analyzing the efficiency of each factory, you would get high positive correlations in output of each machine between the factories.

      • Endre Bakken Stovner says:

        A corollary of this is that dumb and mediocre people are dumb and mediocre in every (intellectual) way. Even Gardner admitted that you would probably need a 120 IQ to be great in any of his multiple intelligences (p. 128, The g factor.)

  22. Patrick Boyle says:

    As it happens I used to have a girl friend who claimed to have an IQ of 160, She had a doctorate and was a professor at Stanford so she could be forgiven for thinking well of herself.

    But I estimated her IQ at only about 125. Her doctorate was in education and she was very bad at math. She wasn’t lying about her IQ so much as she was just honestly confused, She wouldn’t have known a standard deviation from a tie rod. The math pertaining to IQ isn’t particularly difficult but it is clearly beyond the capabilities of most Americans.

    I met her on That wasn’t particularly unusual. I only dated women with doctorates at that time.

    I spent two years developing a competitive product to My site was written in C# with a SQL Server backend. I had considered focusing on the very bright the way other sites focus on seniors or Christians. But the numbers are all wrong. Even an IQ of only 145 means you are one in a thousand. That kind of selection criteria will yield very damn few ‘hits’ anywhere in the country.

    • melendwyr says:

      There’s also the possibility that she did indeed have a 160+ IQ, but wasn’t particularly mathematically gifted. And frankly, her being a woman makes that a bit more plausible than if she were male.
      Linguistics and female-type brains just seem to go together. I’ve been exploring the conlanging community lately, and it’s striking how high the rate of homosexuality among linguists and the language-oriented is.

      • gcochran9 says:

        Since she had a education, I’d give 100-1 odds that she didn’t have an IQ greater or equal to 160. That’s considering that she claimed to.

    • melendwyr says:

      I wonder if there might have been schenanigans with childhood IQ tests involved. Given that the standards for G&T programs were linked to IQ tests, I’ve always wondered if there wasn’t something of an industry to inflate scores in exchange for compensation.
      She might also have had an anomalous high score in childhood that’s not reflective of adult performance.
      Or she could be lying or confused, sure.

    • Brett says:

      My back of the envelope calculation using demographic breakdowns of the U.S. population and estimates of mean population I.Q. gives me an estimate of about 10,000 total men at 160 or higher, about half of them Ashkenazi. If we assume the female distribution is narrower, with a 14 point S.D., then I get about 4,000 women at 160 or higher, about two-thirds of them Ashkenazi.

      Again, not a high population, and probably not a good target market for your dating site, but not zero.

      • gcochran9 says:

        About half of the kids in the SMPY samples were Jewish, circa 1997. So says my informant. And indeed that is what you would expect, given the differences in means. I don’t think they ever published anything about that. But that fraction has to be shrinking, with low Ashkenazi fertility and high rates of intermarriage.

      • j3morecharacters says:

        Presumably less than 5% of them were at any time searching for a partner and many of them were relatives, moved in the same circles and had bumped into each other. Not a market for an internet dating site but for a traditional “yenta” matchmaker providing personal service.

      • Patrick Boyle says:

        Brett has explained why there are so many business failures. It’s those damn envelopes.

        In reality you need a lot more customers signed up than you would think. Since the independent probabilities multiply even just few selected criteria result in almost no ‘hits’ returned. For example, how many blonds do you think are in their thirties, have a college degree and whose favorite movie is ‘Eraserhead’? Add the requirement that she also likes Thai food and there is unlikely to be anyone on the planet who is your ‘ideal’ mate.

        You can get around the tyranny of the math by various techniques to make the criteria soft edged or approximate but it still remains a big problem. If a customer is too explicit in what he wants, he will remain lonely.

  23. Greying Wanderer says:

    The industrial revolution didn’t start in a place where people had been assortatively mating on high IQ for centuries. It started in a place where people had been assortatively mating on low genetic load for centuries (weighted average of brains, looks, health).

    (Admittedly the industrial revolution itself probably messed that process up but still.)

    How many more outliers do you get when you bump up the average by 5 points?

    • Brett says:

      An increase in mean population IQ from 100 to 105, with a constant SD of 15, will increase the number of individuals at or above +4 SD about four-fold, assuming a normal distribution.

      • Greying Wanderer says:

        ty :)

      • ursiform says:

        I believe you are saying that a population with a mean of 105 will have four times more individuals who are >4 SD above the mean of the population with a mean of 100. I.e., a population with a mean of 105 will have four times as many individuals above 160 compared to a population with a mean of 100.

        Just want to be clear, because the fraction of individuals >4 SD above the mean is the same regardless of the mean.

  24. Gottlieb says:

    I understand that high IQS without a previous family inheritance (ie, a family full of intelligent people) tend, by logic, not to reproduce their phenotype high iq, because of their high intelligence is the result of random combination of events and genes.
    Super high IQS always seem to be played based on random combination of events and genes first, because they are recessive and second, that just because they are recessive they are also new. New mutations are more epigenetic than fixed, and need be tested in the environment. The super high IQS are derived from the same mutations that cause autism and etc., so we tend to see the super high IQS as autistic-like.
    The high intelligence in humans is now the extrapolation ability of the species to survive, it is an excess that begins to reduce the fitness is an excess that produces our sophisticated and complex societies, but only if we are animals, this does not seem to matter much in end of the day, what matters is passsar genes on and survive.
    This may help explain high intelligence of Ashkenazi Jews, it is interesting that they are both very inbred (especially in the past) but has also been very exogamous. Theirs group strategy is perfect, they keep inbreeding to improve the recessive traits that produce their high intellects while capturing new blood of the nations where they are. And on the idea that Jews have always sought the intelligence as essential for mating, what we see today including component could be as the future of humanity.
    The Jews have a demographic replacement strategy in which its religious core acts as a repository and maintainer of recessive traits that enhance their cognitive exceptionalities (rabbis and congregants) while the more liberal group catching through inter-ethnic marriages, new blood renew the genetic pool.
    Is a high risk strategy although…
    Ashkenazi practice hybrid vigor and endogamic vigor at same time.
    Darwin was not totally wrong, but if he came from a family with a long history of smart, then he should not have married her cousin.

    • minoritymagnet says:

      “while capturing new blood of the nations where they are.”

      Jews are extremely endogamous. Out-marriers will be excluded from the orthodox core. There is no gene-inflow, only outflow.

      • j3morecharacters says:

        According to the latest estimates, three quarters of the Jews marry non-Jews. Their children enjoy no hybrid vigor, feel uneasy among high IQ people and tend to assimilate to the majority. There is a permanent “boiling off”, leaving a rich, concentrated soup in the pot.

      • gcochran9 says:

        I hear more like 50% intermarriage rate, in the US. Do you have a source for the higher number?

        The half-Jewish people I have know seemed comfortable enough. Sharp, too. But my sample is small.

      • melendwyr says:

        I strongly suspect you two are using different definitions of “Jews”, here.
        In any case, there do seem to be converts even to Orthodox Judaism, so the idea that the gene flow is zero is clearly wrong.

      • gcochran9 says:

        Inward gene flow had to be high in the founding process for the Ashkenazi Jews, since the great majority of their maternal lineages are European. Then for a long time it was very low. Now it’s enormous.

      • Gottlieb says:

        Religious groups works like a demographic repository of secular groups. Look to atheists in white american population. Majority of their fathers are religious. Secular jews are not extremely endogamous and the relationship between the orthodox and secular groups are very strong because the secular jews are responsable to jewish success in western societies. Secular jews are responsable to creation of Israel. Like atheists and religious christians, creatives that are on your majority composed by secular or unreligious, create the civilization and the demographic repository (religious core) maintened the basis and the demographic viability.

      • Matt says:

        There is a permanent “boiling off”, leaving a rich, concentrated soup in the pot.

        Sounds likely, but whether the rich, concentrated soup has a better taste (it may not taste “smarter”, but may taste more “Jewish” or less “cosmopolitan” in other ways) or whether there’ll be very much of it is the interesting question.

  25. Greying Wanderer says:

    “I believe you are saying that…”

    Yes, just saying there are two ways to get to the same point: focus on bumping up the average and get your outliers that way (plus lots of other benefits) or focus solely on the outliers.

  26. Gottlieb says:

    ”According to the latest estimates, three quarters of the Jews marry non-Jews. Their children enjoy no hybrid vigor, feel uneasy among high IQ people and tend to assimilate to the majority. There is a permanent “boiling off”, leaving a rich, concentrated soup in the pot.”

    I don’t believe that all (or majority) half-caste jews are like that you saying. I believe that secular jews tend to marry with high iq gentiles. Well, jews always tend to feel weird or outliers (because they are), but many white and non-white gentiles also feel the same thing and aren’t assimilate in their respective groups.
    Jews, in my perspective, is like a nomadic people or (during great part of their lifetime they were like that) and migratory species tend to be adaptable AND metamorphic.
    I also believe that jews is like a exaggerated creative subgroup of caucasian populations. Think if ”creative anglos” resolve close in a separate group??

  27. Tom says:

    Has Greg Cochran commented on this study?

    The genetic traits between humans and Neanderthals are more likely from a shared ancestry rather than interbreeding, a British study has suggested.

    • gcochran9 says:

      I remember it. Wrong, and kind of embarrassingly behind the data, even at the time. You could tell that the putatively Neanderthal segments in the human genome were much younger than the split between Neanderthals and homo sap (too similar). You could see this pretty clearly in the big paper in Science in May 2010.

      If you looked hard, deep in the supplements of that paper, you could also see signs of another archaic introgression into the Melanesians. I noticed it in the fall, but the Denisovan paper came out not much later, in December 2010 .

  28. The fourth doorman of the apocalypse says:

    Aboriginal advantages? To the best of my knowledge, the native peoples of Australia demonstrate a markedly better-than-Western spatial sense, which can plausibly be attributed to having to navigate through the outback without compasses or GPS for generation after generation.

    It is amusing that those who believe in Evolution by means of Natural Selection because it makes a convenient cudgel to beat religious people around the head are more than happy to accept that Aboriginal Australians developed a strong visual acuity and an in-built ability to navigate through wide-open spaces as a result of selection (over thousands of years) but are unwilling to accept that selection might also have operated in different ways on other people, like farmers and those who had to survive in the cold north, or those who have lived in complex civilizations for thousands of years (here I am thinking of the Chinese.)

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