[andriesm]

The real question is whether genetics is a substantial or a negligible influence on intelligence (or proxy measures like IQ).

If genetics is less than 5 percent I would consider that something worth ignoring.

If it is 10 percent it is substantial enough to make a difference at the extremes.

If it is 20 percent that is real serious business.

Anything higher means we should really sit up and take notice of this fact.

[AnthonyMouse]

Another issue is, what is it that you're trying to use it for?

If you're arguing against a eugenicist then it's not just about the percentage, in that case you have to distinguish between genetic and heritable. Suppose that there are some set of four genes that, in just the right combination, are worth 5 IQ points. That's, by definition, genetic, but it won't have a strong correlation with heritability because every kid has four chances to get the combination wrong. Or, if the combination does something bad, four chances to get it right even if their parents didn't. So past performance is no guarantee of future results.

By contrast, if you're trying to decide whether to allocate more resources to kids who already show promise, you care about the individual's natural potential rather than the statistical probability that it will be similar to their parents, so it doesn't matter what was more likely, it matters what actually happened. And by the point you're performing the evaluation, you can't go back in time and change things like the prenatal environment for someone who is already born, so in that context those things belong in the "nature" column and "nurture" only gets the things you could still affect.

[andriesm]

Surely what people want to "use it for" is completely orthogonal to the science itself?

Let the science science, and policy makers make policy.

I think the problem comes when we want scientists to make policy recommendations.

I think scientists should help us determine what the facts are, not decide what to do about them.

What to do is for courts and democracy and for individuals to decide?

[AnthonyMouse]

Even the choice of which question you want the scientists to answer is inherently political, because it frames the issue and causes the available data to contain the answer to that question instead of some other one, which influences (and therefore can be manipulated to influence) what conclusions can be drawn from the available information.

[rcxdude]

Please look at the examples in the article and consider re-calibrating your numbers here. The lower range of heritability means that it is mostly noise.

[skybrian]

Why is that? Odd that the article claims otherwise:

> 50% may sound like a solid heritability figure, but the associated correlation is rather modest.