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What Is the Flynn Effect?

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  1. Definition

    A phenomenon observed in many countries over the 20th century in which average scores on standardized IQ tests steadily rose from one generation to the next. The size of the rise varies by country, but many studies have reported an average increase of around 3 points per generation (roughly 10 years).

  2. James Flynn's Discovery

    In 1984, New Zealand political scientist James Flynn systematically compiled and published this rising trend after re-analyzing IQ test records from multiple countries. It came to be known as the "Flynn effect" after him.

  3. Several Hypothesized Causes

    Various environmental factors have been proposed as causes, including expanded access to education, improved nutrition, greater familiarity with the format of testing itself, and modern living environments that require handling more complex information. However, the general consensus is that no single factor fully explains the phenomenon.

  4. A Recent Slowdown and Reversal

    A 2018 study by Ole Rogeberg and Bernt Bratsberg, analyzing records from roughly 730,000 Norwegian male conscripts, found that IQ scores peaked with those born around 1975 and have since declined by about 5–7 points per generation among later birth cohorts. Similar declining trends since the mid-1990s have also been observed in Finland, Denmark, France, the UK, and other developed countries.

  5. The Reversal Also Points to Environmental Causes

    The Norwegian study found that within the same family, younger siblings scored lower than their older siblings — supporting the idea that the reversal is more likely driven by environmental changes, such as shifts in educational methods or media habits, rather than genetic factors or demographic changes from immigration.

  6. Not Uniform Across All Countries

    Both the historical rise and the recent reversal of the Flynn effect vary by country and time period — it is not a universally uniform law applied around the world. Some developing countries are reportedly still seeing rising IQ score trends.

What Is the Flynn Effect?

The Flynn effect refers to the phenomenon, observed in many countries during the 20th century, of average scores on standardized IQ tests rising steadily from one generation to the next. Because this shift happened over too short a timeframe to be explained by genetic change alone, it has long been considered strong evidence that environmental factors — education, nutrition, and living conditions — significantly influence intelligence test scores.

Another Contested Theory About Group Size

Like the Flynn effect, there's another well-known concept whose precise figures and interpretation remain subject to academic debate: Dunbar's Number. See our guide to Dunbar's Number to explore it — both concepts share the trait of dealing with statistical tendencies that appear across entire populations.

Frequently Asked Questions

Does this mean people have actually gotten smarter?

It's hard to say simply yes. While IQ test scores have genuinely risen, there is still debate over whether this reflects a broad improvement in actual intellectual ability, or is driven by other factors, like growing familiarity with the test format itself.

Why are people now talking about IQ scores declining recently?

Because studies analyzing IQ records of conscripts in some developed countries — including Norway, Finland, and Denmark — have found scores declining among generations born after the mid-1990s. Researchers believe this reversal, too, is more likely explained by environmental factors like changes in educational methods or living environments than by genetics.