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0 pointsA_D_E_P_T1y ago0 comments

There's this: https://pmc.ncbi.nlm.nih.gov/articles/PMC5985927/

First sentence of the conclusion: "Genetic association studies have confirmed a century of quantitative genetic research showing that inherited DNA differences are responsible for substantial individual differences in intelligence test scores."

The trouble is that, like height, IQ is governed by a vast network of "genes of small effect," so a comprehensive view has proven difficult to nail down. Progress is apparently being made, though slowly.

> There is growing evidence that group IQ heritability isn't evidence of genetic causation.

What evidence do you speak of?

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tptacek1y ago

The Plomin and von Stumm study --- easy to find critiques of it! --- is about heritability. It cited unpublished GWAS data to claim polygenic scores would predict more than 10% of educational attainment, and thus intelligence. The educational attainment GWAS study that was eventually published found less than 5%. And remember, the twin study heritability data that most people cite in threads like this claimed over 50% (twin study heritability numbers for all sorts of traits are apparently overstated by factors of 2-4x, which is wild).†

An example of evidence against the reliability of educational attainment and intelligence heritability statistics: comparing intra-family heritability (across large numbers of families) to population-wide studies: for educational attainment, it turns out there's little correlation between the two; for simpler phenotypical traits, there's almost 100% correlation.

To sum this up:

1. The 2018 Plomin study gives sharply lower genetic/EA numbers than were floating around previously (say, from the Jensen-ist era)

2. Plomin's own numbers were preliminary and overstated

3. Researchers in the field criticized that study nonetheless

4. Subsequent studies on direct heritability and molecular heritability put even lower ceilings on it (basically, all credible behavioral trait heritability work has been done after 2018 --- and in fact this is broadly true of a lot of genetics work, not just trying to statistically mine behavioral traits out of genome scoring)

5. Even those results have flunked basic sanity tests (for instance, getting wildly different results in intra-family vs population-wide studies).

It's not looking good for people fixated on this idea.

† I'm being very loosy-goosey with the numbers and units here

A_D_E_P_TOP1y ago

I don't doubt that there are methodological and empirical problems all around. The scientific literature on these points is a mess.

We might want to look at the fundamentals: How is IQ qualitatively different from height, eye color, schizophrenia -- or any other highly complex, heritable polygenic trait? (One could also extend this to the many traits that animal breeders keep an eye on.) None of them have been fully pinned-down yet, but I don't believe that they can't be fully described in principle.

It's true that GWAS for intelligence explains <5% of variance today, but GWAS for height was in the same position a decade ago. Today polygenic scores for height predict over 40% of variance.

tptacek1y ago

One obvious difference between what is known about the heritability of height and what is known about the heritability of intelligence or educational achievement is that when you put height heritability to the test, for instance by checking to see if the intra-family studies agree with the population-level studies, the height heritability stuff holds up, and the EA/IQ stuff does not. Another might be that successive rounds of study of simple phenotypical traits like height have not demolished previous estimates of heritability, while that has in fact happened in the EA/IQ case.

All this happens before we even reach questions about test-test reliability of IQ, or of whether gene-environmental interactions are uniform between Europe and other population cohorts (they do not appear to be!). It defines away SES confounding (which appears to be a significant issue). It has thus far largely ignored epigenetics. And, of course, for it to mean anything, the hypothesis also has to defend the idea that IQ/EA, at least in its genetic component, is immutable.

All that aside, I'm mostly just here to say that simple heritability statistics don't say what people on HN seem to think they say.

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tptacek1y ago

To sum this up:

1. The 2018 Plomin study gives sharply lower genetic/EA numbers than were floating around previously (say, from the Jensen-ist era)

2. Plomin's own numbers were preliminary and overstated

3. Researchers in the field criticized that study nonetheless

5. Even those results have flunked basic sanity tests (for instance, getting wildly different results in intra-family vs population-wide studies).

It's not looking good for people fixated on this idea.

† I'm being very loosy-goosey with the numbers and units here

A_D_E_P_TOP1y ago

I don't doubt that there are methodological and empirical problems all around. The scientific literature on these points is a mess.

It's true that GWAS for intelligence explains <5% of variance today, but GWAS for height was in the same position a decade ago. Today polygenic scores for height predict over 40% of variance.

tptacek1y ago

All that aside, I'm mostly just here to say that simple heritability statistics don't say what people on HN seem to think they say.

j / k navigate · click thread line to collapse