If the trajectory of IQ tests is to be believed, then intelligence is increasing across the world.
But the real story is more complicated, as researchers at King’s College in London found in a study to be published in the journal Intelligence that examined the steady rise in IQ scores worldwide. They looked at 734 studies and surveys on IQ tests in 48 countries, from 1950 to 2014.
In 1950, people were getting less than half of the answers correct in non-verbal intelligence tests, on average. By 2014, that average had risen to near 70%. But the overarching increase in IQ is skewed by a more rapid increase in IQ scores in developing countries. The data show that in the countries identified as developed—including the US, Europe, South Korea, Japan—scores on the test started higher, with people on average answering just under 60% of answers correctly. Developing countries started lower at under 50% correct on average, but have increased more rapidly.
The greater gains in developing countries reflect increasing access to education, healthcare, and internet access, which allow greater access to practice tests and information. Better education also drives the choice to have smaller families, which allows parents to focus more on educating each child, says study co-author and King’s College PhD candidate Peera Wongupparaj.
Increases in IQ scores have varied among higher and lower performers, with lower and middling scorers making the greatest gains, Wongupparaj tells Quartz. That suggests that we are born with the capability to solve complex problems (the skill that IQ is intended to measure), and that greater access to education and practice is what unlocks those skills. If the capability to solve problems were increasing throughout the population, then the IQ scores would be increasing more uniformly at every performance level, Wongupparaj says.
Similarly, philosopher and psychologist James Flynn, for whom the phenomenon of increasing IQ scores is named, has said that we aren’t likely better problem solvers than we were 60 years ago; rather, we’re being asked to consider and think more critically about the sort of problems that are tested by IQ questions, he told the BBC:
“It’s like a weightlifter and swimmer. They may have the same muscles when they were fertilised in the womb, but they would have different muscles at autopsy, wouldn’t they? So today at autopsy, certain portions of our brain, for example those which use logic and abstraction, would have been exercised more and look differently. Other portions of the brain would have shrivelled a bit.”