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Noah Smith @Noahpinion
, 7 tweets, 2 min read Read on Twitter
1/A quick thread on IQ measurement and public policy.

Many people believe IQ is not a good measure of intelligence.

BUT, even if that's true, we should still worry when we see things that lower IQ!

theguardian.com/environment/20…
2/The reason: If IQ is correlated with true intelligence (whatever that means), then things that reduce IQ will also reduce true intelligence, UNLESS they also increase the unobserved components of intelligence.
3/So if we think that things like air pollution, lead poisoning, and lack of education INCREASE the non-IQ parts of intelligence, then maybe we shouldn't worry when we read that these things are reducing IQ.

But we DON'T think that, do we?! That would be kind of nuts!!
4/In other words, even if you don't believe IQ by itself is a good measure of intelligence, you should still worry when you see IQ going down due to air pollution, lead, lack of education, etc.

Even if the level doesn't matter much, the CHANGE can still matter a lot!
5/So YES, you should be worried about lead's effect on IQ, even if you don't think IQ is a good measure of overall cognitive ability.

npr.org/sections/healt…
6/And YES, you should regard education's positive impact on IQ as a reason to support education, even if you don't think IQ is a good measure of overall cognitive ability.

journals.sagepub.com/doi/abs/10.117…
7/So if your response to an article about how pollution lowers IQ, or education raises IQ, or iodine raises IQ, etc., is "but IQ is hogwash", you're making a big mistake!

IQ changes are a good way to identify some of the things that hurt people's brains.

(end)
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