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The Flynn effect: a meta-analysis.

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The Flynn effect shows IQ scores rising about 2.3 points per decade, with modern tests showing a 2.9 point increase. This meta-analysis confirms the Flynn effect

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Area of Science:

  • Psychology
  • Psychometrics
  • Human Intelligence

Background:

  • The Flynn effect describes the observed increase in intelligence quotient (IQ) scores over time, leading to norm obsolescence in standardized tests.
  • Previous estimations of the Flynn effect magnitude and its moderating factors have been limited by "scorecard" approaches, leading to controversy.
  • A precise understanding of the Flynn effect's magnitude, error of measurement, and moderating variables is crucial for accurate intelligence assessment.

Purpose of the Study:

  • To conduct a meta-analysis to precisely determine the magnitude of the Flynn effect.
  • To establish the error of measurement associated with the Flynn effect.
  • To assess the impact of moderator variables on the Flynn effect's mean effect size across different IQ tests.

Main Methods:

  • A meta-analysis was performed on 285 studies (N = 14,031) conducted since 1951, involving administrations of two intelligence tests with different normative bases.
  • A subset of 53 comparisons (N = 3,951) using modern (post-1972) Stanford-Binet and Wechsler IQ tests was analyzed separately.
  • Moderator analyses examined the influence of study sample, order of administration, age, and ability level on the Flynn effect size.

Main Results:

  • The overall meta-analytic mean Flynn effect was 2.31 standard score points per decade (95% CI [1.99, 2.64]).
  • For modern IQ tests, the mean effect size was 2.93 IQ points per decade (95% CI [2.3, 3.5]), consistent with prior estimates.
  • Study sample type and order of administration significantly moderated the Flynn effect for modern tests, while age and ability level did not.

Conclusions:

  • This meta-analysis provides a precise estimate of the Flynn effect, supporting its continued existence and magnitude.
  • The Flynn effect is robust across different age groups, measures, samples, and performance levels.
  • Findings suggest the Flynn effect is not diminishing and highlight the importance of test norm updates for accurate intelligence measurement.