- Named after researcher James Flynn, the Flynn effect is the long-term rise in average IQ test scores over the 20th century.
- Genetics change far too slowly to explain such rapid gains, so the causes are environmental.
- Since around the 1990s, several countries including Norway, Denmark, Finland, France, and the UK have shown falling rather than rising scores.
- It strongly suggests that intelligence test scores reflect environment and circumstance, not a fixed biological ceiling.
What is the Flynn effect?
Named after researcher James Flynn, the Flynn effect is the long-term rise in average IQ test scores over the 20th century. Across many countries, scores climbed by roughly three points per decade. Because tests are periodically restandardized to keep the average at 100, this steady gain went largely unnoticed at first.
What likely caused the rise?
Genetics change far too slowly to explain such rapid gains, so the causes are environmental. Likely contributors include better nutrition and health, more and longer schooling, smaller families, and a modern world that rewards abstract, scientific reasoning. Familiarity with test-style thinking probably played a part too.
What is the reverse Flynn effect?
Since around the 1990s, several countries including Norway, Denmark, Finland, France, and the UK have shown falling rather than rising scores. A 2018 study by Bratsberg and Rogeberg, using data from hundreds of thousands of Norwegian conscripts, found declines even within families. That within-family pattern points to environmental causes, not changes in genes or migration.
What does the reversal tell us?
It strongly suggests that intelligence test scores reflect environment and circumstance, not a fixed biological ceiling. Proposed factors for the decline include changes in education, reading habits, media use, and the kinds of reasoning daily life now demands. The honest answer is that researchers are still debating which factors matter most.