Average IQ Scores Have Fallen Since 1986. Researchers Still Disagree About Why.
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Global IQ scores rose an average of 2.4 points per decade between 1948 and 1985, then slowed to 1.8 points per decade between 1986 and 2020, according to French cognitive scientist Franck Ramus, whose analysis was published by Polytechnique Insights, the research-communication outlet of France's École Polytechnique. That's a deceleration of the so-called Flynn effect, the well-documented 20th-century rise in average test scores named for researcher James Flynn, not an outright global decline. In several wealthy countries, though, the deceleration became something sharper: an actual, measured drop.
Whether "IQ is falling" or "IQ is still rising, just more slowly" depends heavily on which country and which year range a given study covers, which is a large part of why the topic remains genuinely contested among researchers rather than settled.
Norway's Records Show An Actual Decline, Not Just A Slowdown
The most methodologically decisive evidence comes from Norway. Economists Bernt Bratsberg and Ole Rogeberg analyzed roughly 730,000 IQ test results from Norwegian men who took compulsory military conscription tests between 1970 and 2009, covering birth cohorts from 1962 to 1991, in a study published in the Proceedings of the National Academy of Sciences in 2018. Scores rose through the cohort born in 1975, then declined afterward, roughly 0.2 IQ points per year, equivalent to about seven points across the full span of birth cohorts studied. Critically, the researchers compared brothers within the same families, which let them rule out two of the leading alternative explanations, that the decline reflected either dysgenic fertility patterns or compositional changes from immigration, since neither could produce a decline this large within families sharing the same parents. The drop, like the original Flynn effect rise, appears to be environmental rather than genetic.
Similar patterns, using the same kind of compulsory military or national testing data, have been documented in Denmark, Finland, the United Kingdom, France, the Netherlands and Estonia beginning in the mid-1990s, according to multiple research reviews tracking the phenomenon researchers call the "negative Flynn effect."
The Pattern Splits Along Economic Development, Not Geography Alone
A 2022 review published in the journal Intelligence, examining PISA test results from 48 countries between 2000 and 2018, found that positive Flynn effects have persisted mainly in economically less-developed countries, while trends in the most economically advanced countries were trivial or frequently negative over the same period. The same analysis found that high pre-existing national IQ and school achievement were the strongest predictors of which countries saw declining scores, a pattern the researchers said should narrow global cognitive-ability gaps between countries over coming decades even as it looks, within any single wealthy country, like a worrying local reversal.
The Decline Isn't Uniform Across What IQ Tests Measure
A canonical meta-analysis by researchers Jakob Pietschnig and Martin Voracek, covering studies published between 1909 and 2013, found that gains in crystallized intelligence, the kind of knowledge and vocabulary-based reasoning shaped by education and culture, stopped rising in the 1980s, while gains in fluid intelligence, the capacity for abstract problem-solving independent of learned knowledge, continued. More recent work has found the picture even messier: a 2024 study identified a weakening "positive manifold," the tendency for performance on different cognitive subtests to correlate with one another, suggesting that IQ scores may be measuring an increasingly fragmented set of abilities rather than one unified trait the way they did decades ago. That complicates the basic premise behind any single "IQ is falling" headline, since the sub-scores driving an overall decline aren't always the same ones across countries or studies.
Why Researchers Still Disagree
The leading environmental explanations for the reversal include a "ceiling effect," the idea that the 20th century's gains came from removing specific deficits, poor nutrition, undiagnosed lead exposure, limited schooling, that wealthy countries have now mostly resolved, leaving less room for further improvement; shifts in education away from the abstract, decontextualized reasoning style that fluid-intelligence tests reward; and changes in how people spend their free time, including less sustained reading, that may shape the same cognitive skills IQ tests measure. None of these explanations is fully settled, and they aren't mutually exclusive; a given country's decline could plausibly reflect some combination of all three. What researchers have converged on is what the decline isn't: the within-family evidence from Norway and the environmental parallel to the original Flynn effect rise have left genetic explanations for the recent drop without much support in the peer-reviewed literature, even as the specific mechanism behind it remains an open, actively studied question.
