A response to Sasha Gusev on IQ

The weight of evidence suggests genes matter far more than family environment.

Written by Noah Carl.

Has the heritability of IQ been substantially overestimated due to lack of controls for environmental confounding? That’s the message of two recent articles by Sasha Gusev, an associate professor at the Harvard Medical School.

I should say at the outset that the articles are very much worth reading. With the exception of one or two snarky paragraphs, they are largely free of the churlish tone Gusev became known for on Twitter. And the evidence they present is actually compelling. It’s not just the usual: “twin studies… something something… EUGENICS.” However, this doesn’t mean I’m persuaded by all or even most of the author’s claims.

And some of his claims are rather sweeping indeed. He says that molecular genetics has “thoroughly debunked” the view that “intelligence is just like any other biological trait, with individual differences explained by simple genetic causes that are easily quantifiable and culturally immutable”. (Okay, individual differences in IQ aren’t culturally “immutable”, but we knew that long before molecular genetics came along.) He also says that a trait like IQ “appears to be highly culturally and environmentally dependent” – not just culturally and environmentally dependent but highly so.¹