Misunderstanding the Flynn Effect


The main point that the article seems to be trying to get across is that because IQ scores have risen over time, IQ can’t be genetic in origin. Yes, scores on a g-loaded test rose. Environmental  improvements are almost certainly the cause of this. However, no one claims that IQ is a purely genetic phenomenon, that wouldn’t make sense. Of course environment effects IQ! If we lived in a world where half of all babies had their heads beaten with hammers, I would expect that the average raw performance on IQ tests would be a good deal lower and much more a result of environment than other factors.  The claim is that the variance observed in IQ in modern societies is largely heritable (read: a product of genetic and epigenetic variation). The heritability of IQ (or rather, the variance of IQ attributable to genotype) is still extremely high.

I also don’t really buy the explanations they suggest for the Flynn Effect. Are they really trying to say that schooling is responsible for the improvements? That just doesn’t make sense. Had the Flynn effect been observed before compulsory education showing up, then there might have been something to it. Practice effects have long been known to exist in IQ testing. If you give a Raven’s style pencil-and-paper IQ test to someone who’s never had any sort of test before, then taking their score at face value might be misleading. Of course, that’s not what the article was looking at. They’re looking at young adults in the 1960s. Nearly all of those kids would have had plenty of experience with tests.

They also suggest the increasing demand for abstract thinking as a driver of the Flynn effect. This argument sort of reminds of Steven Johnson’s novel-but-unconvincing idea that rising IQs are a result of the growing complexity of popular culture. These sorts of arguments are a bit better, and there may very well be something to them. Honestly, I don’t know. That being said, it’s not like this reason is anymore convincing than others that have been proposed. Lead levels (known to be associated with childhood IQ drops) in the environment have fallen. Infections in childhood can stunt brain development, so improvements in healthcare for infants, as revealed by the much reduced infant mortality rate, are another possible source of this rise. People may also just be better nourished. There’s lots of stuff at work that the article doesn’t give the proper attention to.

And finally there’s the IQ-doesn’t-matter thing. That’s just empirically not true. It predicts tons of useful stuff.


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