OSLO, July 14 — The long-celebrated Flynn effect, which tracked rising intelligence test scores across many parts of the world over the 20th century, has reversed. A major new study of 579,379 Norwegian men shows that test scores are now declining, and the earliest, steepest falls are concentrated among the sons of high-income fathers. The research, published in 2024, draws on mandatory military conscription tests taken by Norwegian men aged 18 and 19.
Against this backdrop of a broad national reversal, the data reveal a striking socioeconomic fracture. Scores began falling first in the highest income quintile, and that group has experienced the most pronounced decline.
What is at stake is more than a statistical curiosity. The Flynn effect, named after the researcher James Flynn, had long been cited as evidence that human cognitive potential could be lifted by improved schooling, better nutrition, and more intellectually demanding environments. The Norwegian data suggest those gains are now being lost, and unevenly.
Researchers at the Ragnar Frisch Centre for Economic Research in Oslo and the University of Oslo conducted the analysis. They point to environmental factors as the likely drivers: changes in education, nutrition, or media consumption patterns may be reshaping cognitive development in ways that are not yet fully understood.
The wider picture includes a temporary buffer for lower-income groups. Gains from expanded upper-secondary education slowed the decline among sons of less affluent families, but that effect has not been enough to halt the overall downward trend. The data show the reversal is now general across the population.
In the corridors of European social science, this study has prompted urgent questions. Norway is a wealthy, egalitarian society with universal healthcare and strong public education. If cognitive scores are falling there, and falling fastest among the most privileged, the implications for other Western nations could be significant.
The study’s authors have not pinned the reversal on a single cause. Instead, they describe a shift in the environmental mix — the constellation of factors that shape a young person’s cognitive development from childhood through adolescence.
Screen time, changing family structures, altered reading habits, and shifts in school curricula are all plausible contributors, though the data do not isolate any one variable. The next question for researchers will be whether this pattern holds beyond Scandinavia. Comparable conscription data from other European countries, where military service remains mandatory or where cognitive testing is routine, will be closely watched.
If the Norwegian findings are replicated, the end of the Flynn effect may prove to be one of the defining demographic trends of the early twenty-first century.
