Journal article
The Flynn effect for fluid IQ may not generalize to all ages or ability levels: A population-based study of 10,000 US adolescents
Intelligence (Norwood), Vol.77, p.101385
11/2019
DOI: 10.1016/j.intell.2019.101385
PMCID: PMC7176308
PMID: 32322129
Abstract
Generational changes in IQ (the Flynn Effect) have been extensively researched and debated. Within the US, gains of 3 points per decade have been accepted as consistent across age and ability level, suggesting that tests with outdated norms yield spuriously high IQs. However, findings are generally based on small samples, have not been validated across ability levels, and conflict with reverse effects recently identified in Scandinavia and other countries. Using a well-validated measure of fluid intelligence, we investigated the Flynn Effect by comparing scores normed in 1989 and 2003, among a representative sample of American adolescents ages 13–18 (n = 10,073). Additionally, we examined Flynn Effect variation by age, sex, ability level, parental age, and SES. Adjusted mean IQ differences per decade were calculated using generalized linear models. Overall the Flynn Effect was not significant; however, effects varied substantially by age and ability level. IQs increased 2.3 points at age 13 (95% CI = 2.0, 2.7), but decreased 1.6 points at age 18 (95% CI = −2.1, −1.2). IQs decreased 4.9 points for those with IQ ≤ 70 (95% CI = −4.9, −4.8), but increased 3.5 points among those with IQ ≥ 130 (95% CI = 3.4, 3.6). The Flynn Effect was not meaningfully related to other background variables. Using the largest sample of US adolescent IQs to date, we demonstrate significant heterogeneity in fluid IQ changes over time. Reverse Flynn Effects at age 18 are consistent with previous data, and those with lower ability levels are exhibiting worsening IQ over time. Findings by age and ability level challenge generalizing IQ trends throughout the general population.
•When outdated norms are used, the Flynn Effect inflates IQs and potentially biases intellectual disability diagnosis•In a large US-representative adolescent sample, a Flynn Effect was found for IQs ≥ 130, and a negative effect for IQs ≤ 70•IQ changes also differed substantially by age group•A negative Flynn Effect for those with low intellectual ability suggests widening disparities in cognitive ability•Findings challenge the practice of generalizing IQ trends based on data from non-representative samples
Details
- Title: Subtitle
- The Flynn effect for fluid IQ may not generalize to all ages or ability levels: A population-based study of 10,000 US adolescents
- Creators
- Jonathan M Platt - Department of Epidemiology, Mailman School of Public Health, Columbia University, 722 West 168th Street, New York, NY 10032, United States of AmericaKatherine M Keyes - Department of Epidemiology, Mailman School of Public Health, Columbia University, 722 West 168th Street, New York, NY 10032, United States of AmericaKatie A McLaughlin - Department of Psychology, Harvard University, 33 Kirkland Street, Cambridge, MA 02138, United States of AmericaAlan S Kaufman - Yale University, Child Study Center, School of Medicine, 230 S. Frontage Road, New Haven, CT 06519, United States of America
- Resource Type
- Journal article
- Publication Details
- Intelligence (Norwood), Vol.77, p.101385
- DOI
- 10.1016/j.intell.2019.101385
- PMID
- 32322129
- PMCID
- PMC7176308
- NLM abbreviation
- Intelligence
- ISSN
- 0160-2896
- eISSN
- 1873-7935
- Publisher
- Elsevier Inc
- Grant note
- DOI: 10.13039/100000025, name: National Institute of Mental Health, award: T32-MH1304346, R01-MH103291, R01-MH106482; DOI: 10.13039/501100003986, name: Jacobs Foundation; name: OneMind Rising Star Award
- Language
- English
- Date published
- 11/2019
- Academic Unit
- Epidemiology; Injury Prevention Research Center
- Record Identifier
- 9984214674902771
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