The Flynn effect is the rise in intelligence test scores during the 20th century: about 3 IQ points per decade in many countries. It is named after James Flynn, who documented it in the 1980s.
Why tests are re-normed
If people do better over time, old norms give inflated scores. Tests are updated every 15 to 20 years, so the average of 100 always refers to the current population.
Proposed causes
- Better nutrition and health.
- More years of schooling.
- A more abstract environment, with more symbols, screens and hypothetical reasoning.
- Smaller families.
The rise was biggest on abstract reasoning, such as matrices, and smallest on vocabulary and knowledge.
Has it reversed?
In Norway and Denmark, cohorts born since the mid-1970s score slightly lower than earlier ones. A 2018 Norwegian study comparing brothers points to environmental, not genetic, causes.
How big was the rise?
James Flynn showed that scores on IQ tests rose by about three points per decade in many countries during the 20th century. The rise was largest on reasoning tests such as matrices, and smaller on vocabulary and general knowledge.
Why it happened
- Better nutrition and health, especially in childhood.
- More and longer schooling, which trains abstract thinking.
- Smaller families and more stimulating environments.
- Familiarity with tests and with the kind of abstract problems they use.
Is the Flynn effect reversing?
Since the 1990s some countries, such as Norway, Denmark and Finland, show flat or falling scores. A large Norwegian study of brothers (Bratsberg and Rogeberg, 2018) found the decline within families too, which points to environmental causes such as changes in schooling or media, not to genes.
Because of the effect, tests must be re-normed regularly; otherwise everyone would look above average. That is also why the average IQ is always set back to 100.
Frequently asked questions
Who discovered the Flynn effect?
The New Zealand researcher James Flynn documented it in the 1980s; the name was coined by Richard Herrnstein and Charles Murray.
Are people getting less intelligent?
In some countries scores have stopped rising or fallen slightly since the 1990s, most likely for environmental reasons. It does not mean a large or permanent drop.
Sources
- Flynn, J. R. (1987). Massive IQ gains in 14 nations: What IQ tests really measure. Psychological Bulletin, 101(2), 171–191.
- Bratsberg, B. & Rogeberg, O. (2018). Flynn effect and its reversal are both environmentally caused. PNAS, 115(26), 6674–6678.