Unlike referees for academic journals, the blogosphere produces a lot constructive and thought-provoking criticism. Check out Biopolitical and Tyler Cowen‘s responses to my recent post on IQ. Biopolitical immediately brought up an issue worth elaborating on:

I can see no difference between IQ and schooling as matters of policy.

1. We can change schooling. We can implement a successful policy of increasing schooling and, by doing so, achieve some economic benefits.
2. We can change IQ. We can implement a successful policy of increasing people’s IQ and, by doing so, achieve some economic benefits.

But, someone can reply, IQ is heritable!

1. Yes, IQ may be heritable.
2. But years of schooling (or any other measure of schooling) may also be heritable.


1. We can change the mean and the variance of heritable traits.
2. We can even change the heritability of traits.

As a general rule, this is entirely correct. But not for IQ. The interesting thing about IQ isn’t simply that it’s highly heritable, but at least in rich countries it’s been very difficult to find any environmental factor that can enduringly increase IQ. While many people uncomfortable with IQ research seek refuge in Dickens-Flynn, this is actually one of my main inspirations. We know lots of ways to temporarily raise IQ, but virtually nothing that permanently raises it. Even adoption at birth by a high-IQ family has zero apparent effect on adoptees’ adult IQs.

Tyler Cowen brings up the Flynn effect, but he virtually answers his own objection:

Surely this deserves some discussion of the Flynn Effect, that near-universal albeit mysterious process whereby average IQs rise each generation. Should we re-gear government policy to subsidize whatever factors deserve the credit for this phenomenon?

If the Flynn effect is “mysterious” – and it is – it’s going be to awfully hard to subsidize the factors that are responsible for it!

The bottom line is that the popular view that IQ can’t be changed (as economists would say, that it’s “perfectly inelastic”) is literally false but roughly correct for most practical purposes. Better nutrition might help in poor countries, and if someone figured out the cause(s) of the Flynn effect we might be able to permanently make people a lot smarter in rich countries too. But that’s about it.

Next post: Why Tyler underestimates the libertarian implications of IQ research.