WELLINGTON, July 14 — Three points per decade. That was the figure that mattered for generations: the steady, measurable rise in raw IQ scores across the developed world, documented first by James Flynn in his landmark 1987 paper “Massive IQ Gains in 14 Nations.” The bottom line: the Flynn effect, named for the New Zealand-based political scientist, was one of the most robust findings in intelligence research. Now, a 2024 Norwegian study of 579,379 men shows that trend has reversed.
The declines began in the 1970s, and they are hitting hardest among sons of high-income fathers. Flynn, who died in 2020 at age 86, was born in Washington, D.C., and earned his PhD from the University of Chicago.
He taught at the University of Otago in New Zealand from 1967 until his retirement. His 1987 paper brought the phenomenon of rising IQ scores to widespread attention. By the numbers, the Flynn effect had been observed in many developed countries, with scores rising about three points per decade throughout the 20th century.
Investors in human capital will note that this pattern was treated as near-universal for decades.
The reversal that changes the narrative
The 2024 Norwegian study changes that. Researchers examined cognitive test data from 579,379 men, a sample large enough to detect real shifts. The finding: a reversal of the Flynn effect, with declines beginning in the 1970s.
The figure that matters is not just the overall drop, but its distribution. The declines are particularly pronounced among sons of high-income fathers.
That is a striking detail — it suggests the reversal is not simply a story of poverty or disadvantage, but something broader affecting even privileged cohorts. Flynn’s work remains foundational to understanding generational changes in cognitive ability. He was a political scientist and intelligence researcher by training, and his career at the University of Otago gave him the academic freedom to pursue a question that had puzzled psychologists: why raw IQ scores kept climbing, even as the tests were periodically re-normed to keep the average at 100.
His answer — that the gains reflected not raw intelligence but improved ability to think abstractly and classify problems — reshaped the field. The Norwegian data now suggests that environmental factors that once pushed scores upward — better nutrition, more schooling, greater cognitive stimulation — may have plateaued or reversed in their effect.
Or new factors, such as changes in family structure, screen time, or educational methods, may be pulling scores down. The 2024 study does not name a single cause; it reports the statistical fact of decline.
What to watch next
For investors, policymakers, and anyone tracking long-term human capital trends, the stakes are clear. Cognitive ability correlates with productivity, earnings, and innovation. If the Flynn effect has truly reversed across developed nations, the consequences will show up in economic data over the coming decades.
The Norwegian study is one data point — a large one, but still one country. Researchers will now watch for similar patterns in other developed nations that once showed the rise.
The irony is not lost on those who study Flynn’s work. The man who documented the 20th century’s great cognitive rise may now be the baseline against which its 21st-century decline is measured. His 1987 paper changed how we think about intelligence.
The 2024 Norwegian study may change it again.
