IQ tests are “normed”: Your score reflects how you did compared with other people, like being graded on a curve. But the test designers, who set the average in a given year at 100, have to keep “renorming” the tests, adding harder questions. That’s because absolute performance on IQ tests—the actual number of questions people get right—has greatly improved over the last 100 years. It’s called the Flynn effect, after James Flynn, a social scientist at New Zealand’s University of Otago who first noticed it in the 1980s.
So, what explains the rise in scores? There are a lot of possible explanations, and Drs. Pietschnig and Voracek analyze how well different theories fit their data. Genes couldn’t change that swiftly, but better nutrition and health probably played a role. Still, that can’t explain why the change affected adults’ scores more than children’s. Economic prosperity helped, too—IQ increases correlate significantly with higher gross domestic product.
The fact that more people go to school for longer likely played the most important role—more education also correlates with IQ increases. That could explain why adults, who have more schooling, benefited most. Still, the Flynn effect has a strong impact on young children. Education, just by itself, doesn’t seem to account for the whole effect.
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