13.8 points. That is how far average IQ scores among Americans rose between 1932 and 1978, by James Flynn’s 1984 count, a gain of 46 years’ worth of testing. Almost a full standard deviation.
The bottom line: people kept scoring higher even though test makers always reset the scale so that 100 is the average. Flynn worked out that the average American in 1900 would score a 67 on the year-2000 version of the test.
James Robert Flynn was born on April 28, 1934, in Washington, D.C., and died on December 11, 2020. He won a scholarship to the University of Chicago, meant to study mathematics or physics and ended up in moral and political philosophy. He finished his doctorate in 1958, at 24. In 1963 he moved his family to New Zealand, and in 1967 he joined the University of Otago in Dunedin as Foundation Professor of Political Studies and head of the politics department.
A rebuttal that became a discovery
The IQ work began almost by accident. In 1978 Flynn read an article by Arthur Jensen, a Berkeley educational psychologist, arguing that black people scored lower than white people on IQ tests because of genetic differences. Flynn planned a few pages in reply. Then he looked at historical IQ tests and saw the raw scores moving up over time.
A rise that fast could not come from genes. His conclusion: environment shapes IQ more than heredity does. His 1980 book Race, IQ and Jensen made that case.
Critics said schooling might explain the gains. So Flynn turned to Raven’s Progressive Matrices, which use visual patterns instead of words. His 1987 paper, “Massive IQ Gains in 14 Nations: What IQ Tests Really Measure”, found Raven gains of 5 to 25 points across 14 countries. Comparisons across 100 years of birth cohorts in Des Moines, Iowa, and Dumfries, Scotland, showed the same steady climb.
The label came later. Richard Herrnstein and Charles Murray used “Flynn effect” in their 1994 book The Bell Curve. Flynn often debated Jensen and Murray, and the admiration ran both ways.
Why scores rose
Flynn pointed first to education. In a 2013 TED talk he said, “We are educating people to take the hypothetical seriously, to use abstractions, and to link them logically.” The biggest gains showed up in classification and analogies. Health and nutrition are also cited as factors, along with more mentally demanding jobs. With co-worker William Dickens, Flynn proposed a model in which a challenging environment raises IQ and a higher IQ steers people toward more challenging environments.
Does the trend hold?
Some researchers report a “negative Flynn effect,” a reversal of the gains in at least a few developed countries. A 2014 meta-analysis covering 285 studies found a mean gain of 2.31 standard score points per decade and did not support a reversal. Both camps have data.
