Genes and cognitive ability

Nicholas W. Papageorge and Kevin Thom write,

we utilize a polygenic score (a weighted sum of individual genetic markers) constructed with the results from Okbay et al. (2016) to predict educational attainment. The markers most heavily weighted in this index are implicated in neuronal development and other biological processes that affect brain tissue. We interpret the polygenic score as a measure of one type of endowed ability.

Perhaps a newer version of the paper is here.

The paper finds that gene-environment interaction matters. But I think it is important that we now have a genetic score that can serve as a proxy for IQ. Also, this genetic score affects economic outcomes even when educational attainment is controlled for.

By the way, Robert Plomin’s forthcoming book is on my radar. This review points out the obvious, which is that the book will not be well received.

And also, Tyler Cowen points to this paper, which says that it is liberals who attribute outcomes more to genetic factors.

I can only imagine genetic effects being powerful if you hold constant the cultural context. Suppose it were possible to create reliable polygenic scores for the Big Five personality traits, plus cognitive ability. I can imagine that these scores would be useful in predicting outcomes among a group of American teenagers. But if you were to take a random sample of teenagers around the world and use nothing but these scores to predict long-term outcomes, I cannot imagine that this would work. To carry the thought experiment even further, think in terms of plopping people with identical polygenic scores into different centuries.

10 thoughts on “Genes and cognitive ability

  1. I can only imagine genetic effects being powerful if you hold constant the cultural context.

    It doesn’t have to be exactly constant. Overall, the studies show that genetics is a major (often the largest, depending on details) predictor of outcomes for people living ordinary lives in the West. In other words, changing the cultural context from, say, a lower-class apartment block in Chicago to upper-middle-class suburban Oklahoma is probably not as determinative of a many aspects of person’s future as that person’s genes, but being adopted by Saudi royalty or Rwanda peasants would probably be more determinative.

  2. Also, there’s rarely a reason to use a moderately correlated genetic proxy for IQ when reliable IQ tests are cheaper and more accurate.

  3. “I can only imagine genetic effects being powerful if you hold constant the cultural context. ”

    I’d bet the other way: that if you ran similar tests you’d find they’d be ok at predicting the star Geometry students in Plato’s Academy (let no one ignorant of it enter!) or top scorers on the Chinese Imperial examination (with the caveat that a lot of these tests start to become less reliable with increasing genetic distance from the study population).

    This seems especially likely given that there’s a good amount of evidence that high IQs aren’t so much the result of different alleles but the absence of a lot of very mildly deleterious mutations, i.e., ‘genetic load’.

  4. Not all ex-commies in Eastern Europe became successful, but very many of the up & coming communists, along with many older commies, did. And a great disproportionate number of the “very successful” were ex-commies.

    High IQ was one of the characteristics. Drive to be successful, using all means available (including quite a lot under the table), was another.

  5. Another thought experiment. Two pregnant women. Both get the same test result. Your baby has Down’s syndrome. If you’re the progressive secular 34-year-old legal professional, you have an abortion. If you’re the conservative Christian 34-year-old legal professional, you have a child.

    But there aren’t a lot of conservative Christians in Iceland or Norway. So you need to imagine a hundred pregnant women. Ninety-nine have an abortion, and there’s just the one who has a child. This is narrower and deeper without being older.

    So this one woman is an extreme outlier. The vast majority of women in Iceland and Norway are eugenicists. Almost everybody agrees that a child with Down’s syndrome shouldn’t exist. These days almost everybody, left and right, is an early-1900s Progressive, and the holdouts are a tiny band of right-wing traditionalists who think eugenics is barbarous.

    What economic outcomes are the ninety-nine women predicting for someone with Down’s syndrome? Never going to be a lawyer or a judge. Never going to get a mortgage. Never going to get into a good school and appear on the Dean’s List.

    If the vast majority of everybody thinks that people with Down’s syndrome shouldn’t exist, then it makes sense to see there’s a widespread support for the idea that genetics is real, combined with some lying about the two or three highly specific exceptions to biological reality.

    • You seem to have a point that you’re trying to make, but you also seem a bit confused. For example, you seem to think the “idea that genetics is real” is in question. Genes are as real as any other little squiggly think you can see in a microscope. With a sufficiently powerful microscope and the right dyes, you can take any cell from a living human and see whether the person has Down’s syndrome (to use your example). Just count the chromosomes: 46 is normal, 47 means an extra chromosome (a trisomy – three versions of a chromosome, instead of the normal 2). Down’s syndrome is an extra copy of chromosome 21, and is the only survivable trisomy. In fairness, your example was the easiest case – Down’s syndrome is one of the least subtle genetic defects.

      It seems like you are disturbed by the implications of genetics for society, and that’s reasonable. So am I. But the way you’ve formulated your critique, I can’t quite figure out what you’re trying to say or what you’re suggesting be done. I encourage you to think it over, keeping in mind that the geneticists aren’t stupid – the generally accepted results of the field are backed by convincing evidence.

    • I’m thinking of the Lady Gaga song Born This Way. I’m thinking of the vegetarians and vegans who practice eugenics and believe that meat is murder. I’m thinking of the doublethink at Google. I’m thinking of people who used to know when they were in school that they had high IQs and some of their friends did not.

      If gay men, gay women and straight women are all part of nature, why make an exception for straight men? Why is their sexuality, on its own, artificial? Mere cultural conditioning? Easily fixed with a treatment of conversion therapy? That’s confusing to me.

      What’s not confusing is this no-brainer of a thought experiment. Who is more likely to have personally put into practice a policy of eugenics? The woman on the left or the woman on the right? That’s obvious.

      If you’re a eugenicist in practice, you implicitly accept that genetics is real, no matter what you say out loud when Larry Summers is on the ducking stool and you’re shouting about drowning him. It doesn’t matter what you say in your official capacity as the Dean of Harvard Law (“As an educational institution, we are especially dedicated to exposing to the light of inquiry false views about individuals or groups.”)

      The hypocrisy isn’t disturbing. Logical inconsistency isn’t disturbing. It’s more disgusting than disturbing, in the sense that any logical error is gross and ugly and lacking in elegance. People ought to face up to what they actually believe.

      • That people ought to face up to what they actually believe? That people could just believe whatever’s convenient for them, or they could make an effort to be consistent instead?

        If you believe your doctor when she’s talking about Down’s syndrome, then what about the controversial claim that women have two X chromosomes? Too risky in 2018 to make that claim? If “biological woman” is an offensive term, think up an acceptable way to say the same thing. But don’t join the mob. The emperor has no clothes.

        The emperor simultaneously says that a woman is essentially a better version of a man and also that “a woman” is an essentially meaningless term. One of these claims cancels out the other one. If women are less aggressive, less violent and less selfish than men, then these are claims about women in their essence. So which is it? Do women exist or don’t they? People have to choose.

        People have to apply a little scrutiny to their own beliefs. Dilation and extraction, but not lethal injection? Guns for cops, but not civilians too? Irish nationalism, but not the Israeli kind? Or the belief that everybody is Born This Way (Lady Gaga) except for straight men, who have been bamboozled by the patriarchy (themselves) into this false consciousness about the waist-to-hip ratio and needing to out-earn their wives?

        Or with IQ tests. Should I suppose the existence of a hidden Ashkenazi conspiracy to rig all these tests in order to humiliate and oppress the underprivileged Sephardic community? A conspiracy so vast that our Ashkenazi oppressors colluded with Chinese communists in the service of Chinese Ashkenazi supremacy? Or maybe all the geeks at Google were just given too much encouragement in school? So it’s not because they were smart that they always got good grades. The underachievers weren’t encouraged enough, and the overachievers were encouraged too much?

        • On the one hand, I also dislike hypocrisy. On the other hand, I recognize that every society’s guiding narrative is inevitably a mishmash of a bunch of conflicting ideas that are momentarily united for reasons of politics.

          On the gripping hand, I suspect that hypocrisy is necessary. It seems to me that our society incorporating a realistic view of genetic effects into our guiding narrative in a constructive manner is unlikely. Monkeys-typing-Shakespeare unlikely.

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