May 25, 2005

IQ falling?

The Flynn effect refers to the increase in IQ in recent history in several populations around the world. Several explanations have been proposed for this effect, but a new study from Denmark, replicating a previous one from Norway indicates that the Flynn effect has ceased in the 1990s, and indeed IQ has slightly dropped in recent years to early '90s levels.

Personality and Individual Differences (Article in Press)

A long-term rise and recent decline in intelligence test performance: The Flynn Effect in reverse

Thomas W. Teasdale and David R. Owen


In the 1980s reviewed evidence indicated that, through the preceding decades of the last century, population performance on intelligence tests had been rising substantially, typically about 3–5 IQ points per decade, in developed countries. The phenomenon, now termed the ‘Flynn Effect’, has been variously attributed to biological and/or to social and educational factors. Although there is some evidence to suggest a slowing of the effect through the 1990s, only little evidence, to our knowledge, has yet been presented to show an arrest or reversal of the trend. Substantially replicating a recent report from Norway, we here report intelligence test results from over 500,000 young Danish men, tested between 1959 and 2004, showing that performance peaked in the late 1990s, and has since declined moderately to pre-1991 levels. A contributing factor in this recent fall could be a simultaneous decline in proportions of students entering 3-year advanced-level school programs for 16–18 year olds.


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