If, on the other hand, heritability is high, then throwing more effort/money at how we do education currently should not be expected to improve SAT scores
I agree with spkoc that this conclusion doesn’t necessarily follow from high heritability. I think it would follow from high and stable heritability across multiple attempted interventions.
An exaggerated story for the point I’m about to make: imagine you’ve never tried to improve SAT scores, and you measure the heritability. You find that, in this particular environment, genetic variance explains 100% of SAT scores. You can predict someone’s SAT scores perfectly just by looking at their genome. You decide to take the half of the population with the highest predicted scores, and keep the SAT a secret from them until the day they take the test. And for the lower half, you give them dedicated tutors to help them prepare. Given the 100% heritability, you expect scores to stay exactly the same. But wait! What no one told you was that before your intervention, the learning environment had been magically uniform for every student. There had been no environmental variance at all, and so the only thing left to explain test scores was genetics. What you didn’t realize is that your heritability estimate gave you no information at all about how environmental changes would affect scores—because there was no environmental variance at all!
A single heritability measurement only tells you, roughly, the ratio of “[existing environmental variance] times [sensitivity to environmental variance]” to “[existing genetic variance] times [sensitivity to genetic variance]”. But it doesn’t do anything to disentangle the sensitivities-to-variances from the actual variances. What if there’s practically zero variance in the environment, but a high sensitivity of the trait you’re looking at to environmental variance? You’d find heritability is very high, but changes to the environment will cause large decreases to heritability. Same thing with genes: what if your trait is 100% determined by genes, but it just so happens that everyone has the exact same genes? You’d find that genetic variance explains zero percent of your trait, but if you then tried some genetic engineering, you’d find heritability shoot upward.
In order to disentangle the “sensitivity of X to environmental variance” from “the level of environmental variance”, you’d have to run multiple interventions over time, and measure the heritability of X after each one (or be confident that your existing environment has lots of variance).
True, but “high and stable heritability” across hundreds (perhaps thousands) of attempted interventions is a pretty good description of the real-world results of education research and practice. See Freddie DeBoer’s “Education Doesn’t Work” for a brief treatment or Kathryn Paige Harden’s The Genetic Lottery for a book-length version.
I agree with spkoc that this conclusion doesn’t necessarily follow from high heritability. I think it would follow from high and stable heritability across multiple attempted interventions.
An exaggerated story for the point I’m about to make: imagine you’ve never tried to improve SAT scores, and you measure the heritability. You find that, in this particular environment, genetic variance explains 100% of SAT scores. You can predict someone’s SAT scores perfectly just by looking at their genome. You decide to take the half of the population with the highest predicted scores, and keep the SAT a secret from them until the day they take the test. And for the lower half, you give them dedicated tutors to help them prepare. Given the 100% heritability, you expect scores to stay exactly the same. But wait! What no one told you was that before your intervention, the learning environment had been magically uniform for every student. There had been no environmental variance at all, and so the only thing left to explain test scores was genetics. What you didn’t realize is that your heritability estimate gave you no information at all about how environmental changes would affect scores—because there was no environmental variance at all!
A single heritability measurement only tells you, roughly, the ratio of “[existing environmental variance] times [sensitivity to environmental variance]” to “[existing genetic variance] times [sensitivity to genetic variance]”. But it doesn’t do anything to disentangle the sensitivities-to-variances from the actual variances. What if there’s practically zero variance in the environment, but a high sensitivity of the trait you’re looking at to environmental variance? You’d find heritability is very high, but changes to the environment will cause large decreases to heritability. Same thing with genes: what if your trait is 100% determined by genes, but it just so happens that everyone has the exact same genes? You’d find that genetic variance explains zero percent of your trait, but if you then tried some genetic engineering, you’d find heritability shoot upward.
In order to disentangle the “sensitivity of X to environmental variance” from “the level of environmental variance”, you’d have to run multiple interventions over time, and measure the heritability of X after each one (or be confident that your existing environment has lots of variance).
True, but “high and stable heritability” across hundreds (perhaps thousands) of attempted interventions is a pretty good description of the real-world results of education research and practice. See Freddie DeBoer’s “Education Doesn’t Work” for a brief treatment or Kathryn Paige Harden’s The Genetic Lottery for a book-length version.