OSLO, July 14 — A comprehensive study of nearly 580,000 Norwegian men has documented a sustained decline in intelligence test scores beginning in the 1970s, directly challenging the long-established Flynn effect that had recorded rising IQ scores throughout the 20th century. The study, published in 2024, analyzed scores from 579,379 men born between 1962 and 1991. All were assessed as part of Norway’s mandatory military conscription program, providing what researchers describe as a comprehensive national sample.
According to the data, the earliest and steepest declines occurred among sons of high-income fathers. This wealthier group experienced the most pronounced drop in scores.
Researchers involved in the study have not identified a single cause for the reversal. They point to several possible contributing factors, including changes in family structure, reduced cognitive stimulation, and shifts in educational priorities. None of these have been confirmed as the primary driver.
The record shows that expanded upper-secondary education temporarily slowed the decline among men from lower-income backgrounds. This educational expansion appears to have acted as a buffer for those groups, but it did not halt the overall downward trend.
The Flynn effect, named after researcher James Flynn, documented rising raw intelligence test scores across multiple nations for most of the 20th century. The Norwegian data now presents a comprehensive national challenge to that narrative. The study’s strength lies in its near-total population coverage.
Because military conscription was mandatory for Norwegian men during the period studied, the test results capture the full range of cognitive ability across socioeconomic groups. The birth years span three decades, from 1962 to 1991, allowing researchers to track changes across generations. The decline’s concentration among wealthier families is the detail that has drawn the most attention from analysts.
The new data suggests that whatever is driving the shift is hitting higher-income households first and hardest. Researchers caution that the findings from Norway may not directly translate to other countries.
But the scale of the dataset — nearly 580,000 subjects — makes it one of the most robust examinations of generational intelligence trends ever conducted. The study raises questions that extend beyond academic psychology. No follow-up study has been announced, and researchers have not indicated when additional data from later birth cohorts might become available.
The current study’s authors have called for further investigation into the mechanisms behind the decline, particularly the factors affecting higher-income families. For now, the Norwegian data stands as the most detailed record yet of a trend that, if confirmed elsewhere, would mark a fundamental shift in the trajectory of human cognitive development.
