OSLO, July 14 — For decades, the notion that each generation might be slightly smarter than the last — the so-called Flynn effect — has been a fixture of psychological and educational debate. Against this backdrop, a new study from Norway, drawing on an immense pool of military conscription data, suggests that the trend may have reversed, and that the decline is most pronounced among the country’s highest earners.
The research, which analysed the test scores of 579,379 Norwegian men born between 1962 and 1991, draws on conscription records from 1970 to 2009. The cognitive test itself measures general ability across verbal, arithmetic, and spatial reasoning, with results standardised to a mean of 100 and a standard deviation of 15.
The data was sourced from Statistics Norway and the Norwegian Armed Forces, and the study controlled for birth year, father’s income, and education level. The headline finding is a decline of approximately 0.2 to 0.3 IQ points per decade across the entire sample. But the wider picture is more nuanced, and the figures shift sharply when broken down by income.
Among men in the highest income quintile, the drop was steeper — up to 0.5 points per decade. This is the group that, in the corridors of social science, has often been assumed to enjoy the greatest cognitive advantages: better schooling, more resources, and greater environmental stimulation.
That the sharpest decline appears here has already begun to generate discussion among researchers about what is at stake for societies that rely on a highly educated elite. The lowest income quintile tells a different story. Initially, this group saw a small gain of about 0.1 points per decade, a rise that researchers attribute to the expansion of educational access.
But that modest improvement did not last. In later years, even this group began to decline, mirroring the broader trend. What is at stake in these numbers is more than academic curiosity.
IQ scores, for all their limitations, correlate with a range of life outcomes, from job performance to health. A sustained decline, especially among the most advantaged, could signal shifts in the cognitive environment that are not yet fully understood.
The study’s Norwegian setting is significant. Norway has long been a laboratory for social science, thanks to its comprehensive national registries and universal military conscription, which ensures that nearly the entire male population is tested. The data set, spanning four decades and nearly 600,000 men, offers a statistical power that few other countries can match.
Yet the findings also raise questions that go beyond Scandinavia. If cognitive scores are falling among the highest earners in a wealthy, egalitarian society, what might the trend look like in nations with greater inequality or weaker educational systems?
The answer, for now, remains unclear. Researchers will now be watching to see whether the pattern holds for women, and whether later birth cohorts — those born after 1991 — continue the decline. The data set ends in 2009, meaning the most recent generation of young adults is not yet captured.
Against this backdrop, the Norwegian study is likely to become a reference point in a growing international conversation about the future of human intelligence.
