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Steve Stewart-Williams @SteveStuWill
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THREAD: 12 Things Everyone Should Know About IQ

1. IQ is one of the most heritable psychological traits – that is, individual differences in IQ are strongly associated with individual differences in genes (at least in fairly typical modern environments). www18.homepage.villanova.edu/diego.fernande…
2. The heritability of IQ *increases* from childhood to adulthood. Meanwhile, the effect of the shared environment largely fades away. In other words, when it comes to IQ, nature becomes more important as we get older, nurture less. pdfs.semanticscholar.org/7a6b/ad93d88b0…
3. IQ scores have been increasing for the last century or so, a phenomenon known as the Flynn effect. journals.sagepub.com/doi/full/10.11… (N ≈ 4 million)

(Note that the Flynn effect shows that IQ isn't 100% genetic; it doesn't show that it's 100% environmental.)
4. IQ predicts many important real world outcomes.

For example, though far from perfect, IQ is the single-best predictor of job performance we have – much better than Emotional Intelligence, the Big Five, Grit, etc. onlinelibrary.wiley.com/doi/10.1002/jo… vox.com/2016/5/24/1172…
5. Higher IQ is associated with a lower risk of death from most causes, including cardiovascular disease, respiratory disease, most forms of cancer, homicide, suicide, and accident. sciencedirect.com/science/articl… (N = 728,160)
6. Higher IQ is associated with lower rates of most forms of mental illness. ncbi.nlm.nih.gov/pmc/articles/P… (N = 1,049,663)
7. More generally, IQ tests are among the most reliable, predictive measures in psychology – one of the field's crowning achievements. aeon.co/ideas/how-clev…

If IQ isn't a valid concept, no concept in psychology is valid.
8. Despite this, many people are allergic to the concept of IQ. Ironically, this includes many intellectuals. books.google.com.my/books?id=ePNi4…
9. Perhaps as a result, there's some evidence that researchers are less likely to publish studies showing a link between IQ and grades – the reverse of the usual publication bias for positive findings. sciencedirect.com/science/articl…; although see researchgate.net/publication/32…
10. The antipathy to IQ is unfortunate. IQ predicts all things good. Interventions to boost IQ (such as salt iodization) could greatly enhance human well-being. centroeinaudi.it/images/stories…

Conversely, IQ-denial could cause real harm by stalling the development of such interventions.
11. IQ testing has other potential benefits as well. One of my favourite studies of the last few years found that universal IQ screening boosts the number of poor, female, and minority students in gifted education. pnas.org/content/113/48…

Figure: theatlantic.com/education/arch…
12. Last but not least, here's a list of ten common myths about IQ. books.google.com.my/books?id=nvbMB… HT @StuartJRitchie
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