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What is intelligence? Beyond the Flynn effect

Abstract

Around their 18th birthday, basically all Dutch males born between 1934 and 1964 unknowingly took part in a study of the malleability of intelligence. When these young men appeared before the Dutch military draft board, they took a non-verbal IQ test based on Raven’s (1960) Progressive Matrices. With a little help from Piet Vroon, James Flynn (1987) discovered that those born in 1934 (cohort of 1952) scored on average 20 IQ points lower on the test than those born in 1964 (cohort of 1982). This suggested that in only 30 years, the Dutch male population had shown an increase of more than one standard deviation in average IQ. Flynn (1987) also documented this gain in average IQ in 13 other countries over the course of the 20th century and the effect is now commonly known as the Flynn effect. The Flynn effect raises many questions: How can IQ be substantially heritable, yet show such strong gains that appear to be due to environmental factors? Were Dutch males in 1982 so much smarter than Dutch males in 1952?

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Correspondence to Jelte M. Wicherts.

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Wicherts, J.M. What is intelligence? Beyond the Flynn effect. NEJP 64, 41–43 (2008). https://doi.org/10.1007/BF03076406

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Keywords

  • Differential Item Functioning
  • General Intelligence
  • Verbal Intelligence
  • Differential Item Functioning Analysis
  • Comprehension Subtest