OSLO, July 14 — The scene in cognitive science is shifting under researchers’ feet. A new Norwegian study of 579,379 men documents a reversal of the long-observed rise in IQ scores, a trend that had held steady for most of the 20th century. The study, published in 2024, tracks the raw data: IQ scores rose by about 3 points per decade throughout the 1900s, a phenomenon named the Flynn effect after James Flynn in the 1980s.
That climb now appears to have stopped. The decline began in the 1970s, and the drop is most pronounced among sons of high-income fathers.
This is not a small blip in a single data set. The Norwegian study adds to a growing body of evidence that the Flynn effect may be ending — or even reversing — in developed countries. The history of IQ testing itself reaches back to the early 20th century.
The first modern test was created by Alfred Binet and Theodore Simon in 1905 in France. Lewis Terman adapted that test for American use in 1916, producing the Stanford-Binet test, which became widely used across the United States.
For decades, the story was one of steady gains. Each generation scored higher than the last. The Flynn effect became a celebrated puzzle — no one was entirely sure why it happened, but it was consistent.
Now the picture is different. The Norwegian study, which examined data from 579,379 men, shows the reversal most sharply among the sons of high-income fathers. That detail is striking.
The study is part of a cluster of recent findings from developed nations that show similar patterns. The Flynn effect, it appears, may have peaked.
What comes next is unclear. The study itself does not propose a single cause. The Norwegian data is clean and large.
A sample of nearly 580,000 men gives statisticians room to work. The finding that the decline is strongest among the sons of high earners complicates easy narratives.
The question now is whether the trend accelerates. The 2024 study documents a reversal beginning in the 1970s — that is a half-century of data pointing in one direction. For now, the Flynn effect — that steady, decades-long climb — belongs to history.
The new chapter is still being written.
