Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions

• Published in: Child development Vol. 93; no. 1; pp. e47 - e58
• Main Authors: Giangrande, Evan J., Beam, Christopher R., Finkel, Deborah, Davis, Deborah W., Turkheimer, Eric
• Format: Journal Article
• Language: English
• Published: United States Wiley 01.01.2022; Blackwell Publishing Ltd
• Subjects: Adolescent; Age Differences; Between-subjects design; Child; Childhood; Children; Cognitive Ability; Early Adolescents; Environmental aspects; Environmental factors; Environmental Influences; Genetics; Humans; Intelligence; Intelligence - genetics; Intelligence Quotient; Intelligence Tests; Monozygotic; Multilevel Analysis; Scores; Standardization; Twin studies; Twin Studies as Topic; Wechsler Scales
• ISSN: 0009-3920; 1467-8624; 1467-8624
• DOI: 10.1111/cdev.13675

This study investigated the systematic rise in cognitive ability scores over generations, known as the Flynn Effect, across middle childhood and early adolescence (7–15 years; 291 monozygotic pairs, 298 dizygotic pairs; 89% White). Leveraging the unique structure of the Louisville Twin Study (longitudinal data collected continuously from 1957 to 1999 using the Wechsler Intelligence Scale for Children [WISC], WISC–R, and WISC–III ed.), multilevel analyses revealed between‐subjects Flynn Effects—as both decrease in mean scores upon test re‐standardization and increase in mean scores across cohorts—as well as within‐child Flynn Effects on cognitive growth across age. Overall gains equaled approximately three IQ points per decade. Novel genetically informed analyses suggested that individual sensitivity to the Flynn Effect was moderated by an interplay of genetic and environmental factors.