New study shows reversed Flynn-effect: no more rising IQ’s?

I just received this study via @wduyck and it confirms what other research has shown in different regions: the Flynn-effect has stopped.

As a quick reminder, what is the Flynn-effect?

From Wikipedia:

The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores measured in many parts of the world from roughly 1930 to the present day.

But does this increase means on tests mean that we are actually getting smarter (often described as “g”)? Flynn himself already has doubts, e.g. education more ad more mimicking IQ-tests could be also an explanation. Steven Johnson thinks it’s also because of the rising complexity of popular culture.

Or maybe it’s because of lead? Or because of better and more guessing? Or other reasons?

Maybe we can add new questions to this: why has it stopped or even reversed? Becayse This study now shows:

  • Spatial perception scores decreased from 1977 to 2014 in German-speaking countries.
  • We observed an inverse u-shaped trajectory of IQ test score changes.
  • Changes remained robust when controlling for age, sample type, and sex.
  • Decreasing performance may be due to decreasing psychometric g.

Abstract of the study:

Generational IQ changes (the Flynn effect) have been shown to be predominantly positive but differentiated according to IQ domains and countries. However, evidence from recent studies points towards a decrease of the Flynn effect globally or even a reversal in some countries. In the present meta-analysis, we show an inverse u-shaped trajectory of IQ test performance changes in a large number of samples (k = 96;N = 13,172) on a well-known test for spatial perception (the three-dimensional cubes test, 3DC) in German-speaking countries over 38 years (1977–2014). Assessment of both item response theory-based measures as well as more standard measures of classical test theory showed initial increases and a subsequent decrease of performance when controlling for age, sample type (general population vs. mixed samples vs. university students) and sex. Our results suggest saturation and diminishing returns of IQ increasing factors (e.g., life history speed) whilst negative associations of IQ changes with psychometric g may have led to the observed IQ score decrease in more recent years.


6 thoughts on “New study shows reversed Flynn-effect: no more rising IQ’s?

  1. This isn’t hard to explain.

    “Spatial perception scores decreased from 1977 to 2014 in German-speaking countries.”

    When you look at when lead regulations were implemented and the 20 year lag time for their effect, you’d expect the impact of lead to be seen in the late 1900s to early 2000s.

    In Britain, for example, the earliest lead regulation was passed in the late 1970s and the most recent lead regulation in the mid 1990s. So, you’d expect changes in IQ and violent crime rate to accordingly follow in the 1990s and 2010s. I couldn’t find exact changes of average iQ by year over that time, but in Britain there was a decrease of violent crime over that time.

    All of this fits perfectly the lead toxicity hypothesis. People just forget about the delayed effect. It takes approximately 20 years for a generation of children to reach the age when most crimes are committed.

    Mystery solved!

    1. So you are saying the the first and second world war only happend because violent people had lead pipes and were by intoxication not intelligent enough to go to war. Correlation ain’t causation.

      1. There has been decades of research on lead toxicity. This involves using such methods as the dose response curve that is used to prove the efficacy of pharmaceuticals. That is how scientific researchers determine causation. I can’t force you to inform yourself, but I can suggest that being informed is better than the alternative.

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