The Flynn Effect Explained: Why IQ Scores Rose for a Century

What is the Flynn effect?

In psychology, the Flynn effect is the observation that average scores on IQ tests rose substantially over the twentieth century — by roughly three points every decade in many countries. The pattern is named after political scientist and researcher James Flynn, who brought it to wide attention in the 1980s, though earlier test-makers had already noticed that norms kept drifting upward.

The simplest way to picture it: if you gave today's test, with today's scoring, to people from several generations ago, their average score would come out well below 100 — not because they were less capable in daily life, but because the test is normed against a more recent, higher-scoring population. The gains show up most strongly on abstract-reasoning tasks and least on tests of general knowledge or vocabulary.

Why did IQ scores rise over time?

There is no single agreed cause. Genes cannot change meaningfully in a few generations, so researchers look to the environment. The leading candidate explanations, usually thought to act together, are:

• Better nutrition and health, especially in early childhood, supporting brain development.
• More and longer schooling, which trains the exact abstract, classifying style of thinking that IQ tests reward.
• Smaller families and more adult attention per child.
• More cognitively demanding work, media, and technology in everyday life.
• A cultural shift toward abstract, scientific reasoning — what Flynn called putting on 'scientific spectacles' and reasoning about hypotheticals and categories.
• Greater familiarity with tests and the kinds of puzzles they use.

Is the Flynn effect still happening today?

It depends where you look, and the evidence is mixed. In many developing countries, where nutrition and schooling are still improving rapidly, gains appear to be continuing. In several wealthy countries, however, studies since the 2000s suggest the rise has stalled or even reversed.

A widely cited Norwegian study (Bratsberg & Rogeberg, 2018) found that IQ scores there peaked for people born in the mid-1970s and then declined — and, importantly, that the decline appeared within families, pointing to environmental rather than genetic causes. Similar slowdowns have been reported in some other developed nations, though findings vary by country and test.

What the Flynn effect means for your IQ score

If average raw performance kept rising, why is the average IQ always 100? Because tests are periodically re-standardized against a fresh, representative sample, which resets the mean back to 100. The Flynn effect is, in a sense, the reason re-norming is necessary in the first place.

So your IQ score is always relative to a recent comparison group of people your own age — not to your grandparents. A score of 100 today and a score of 100 fifty years ago both mean 'average for the time', even though the underlying raw performance differs.

Criticisms and limitations

The Flynn effect is well documented, but what it means is contested. The main cautions:

• Rising scores may reflect gains on the specific skills tests reward — abstract classification and on-the-spot problem solving — rather than a rise in general intelligence (often written as 'g').
• It does not mean past generations were unintelligent. People a century ago reasoned effectively within their own world; the gains are largest on the abstract tasks modern schooling emphasises.
• Some of the change could involve measurement artifacts — shifting test content, motivation, or test familiarity — rather than ability alone.
• The size, continuation, and reversal of the effect vary by country, era, and test, so global generalisations are risky.

In short, the Flynn effect is a real and important pattern, but the evidence on its exact causes — and on whether it is now reversing — remains limited. It is best read as a reminder that IQ scores are relative to a time and place, not absolute measures of worth.