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Cited by 478Cognitive Abilities and TestingGenetic Associations and EpidemiologyIntergenerational and Educational Inequality Studies

The heritability of IQ

Devlin, B., Daniels, Michael, Roeder, Kathryn·1997·Nature
DOI 10.1038/41319
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Abstract

IQ heritability, the portion of a population's IQ variability attributable to the effects of genes, has been investigated for nearly a century, yet it remains controversial. Covariance between relatives may be due not only to genes, but also to shared environments, and most previous models have assumed different degrees of similarity induced by environments specific to twins, to non-twin siblings (henceforth siblings), and to parents and offspring. We now evaluate an alternative model that replaces these three environments by two maternal womb environments, one for twins and another for siblings, along with a common home environment. Meta-analysis of 212 previous studies shows that our 'maternal-effects' model fits the data better than the 'family-environments' model. Maternal effects, often assumed to be negligible, account for 20% of covariance between twins and 5% between siblings, and the effects of genes are correspondingly reduced, with two measures of heritability being less than 50%. The shared maternal environment may explain the striking correlation between the IQs of twins, especially those of adult twins that were reared apart. IQ heritability increases during early childhood, but whether it stabilizes thereafter remains unclear. A recent study of octogenarians, for instance, suggests that IQ heritability either remains constant through adolescence and adulthood, or continues to increase with age. Although the latter hypothesis has recently been endorsed, it gathers only modest statistical support in our analysis when compared to the maternal-effects hypothesis. Our analysis suggests that it will be important to understand the basis for these maternal effects if ways in which IQ might be increased are to be identified.

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  • Failure to include maternal effects in heritability models when maternal effects are present can lead to inflated estimates of direct additive genetic effects and an incomplete risk architecture.

    “Failure to include maternal effects in heritability models, when maternal effects are present, can lead to inflated estimates of direct additive genetic effects (36) and the formulation of an incomplete risk architecture.”

    From Maternal Effects as Causes of Risk for Obsessive-Compulsive Disorder (2020) · cites this paper as [36]

  • Maternal effects explain a notable share of variation in traits linked to ASD, such as preterm birth and IQ.

    “Maternal effects have been associated with a substantial proportion of the variation in several traits associated with ASD, including preterm birth 5 and intelligence quotient.6”

    From Association of Genetic and Environmental Factors With Autism in a 5-Country Cohort (2019) · cites this paper as [5]

  • Earlier work has applied liability models with full siblings and cousins to estimate additive genetic, shared environmental, and nonshared environmental effects for other outcomes.

    “Liability models using full siblings and cousins to estimate A, C, and E have been used earlier and for other outcomes (eg, skin cancer, 18,19 M component on preterm birth 5 and preeclampsia, 20,21 and comorbidity of 2 diseases).22”

    From Association of Genetic and Environmental Factors With Autism in a 5-Country Cohort (2019) · cites this paper as [5]

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Authors
Devlin, B., Daniels, M., & Roeder, K.
Affiliations
  • University of Pittsburgh (US)
  • Carnegie Mellon University (US)
Corresponding author
Devlin, B.
ORCID
Venue
Nature
Publisher
Springer Science and Business Media LLC
Published
1997-07-31
Volume
388
Issue
6641
Pages
468-471
ISSN
  • 0028-0836 (ISSN-L)
  • 1476-4687
DOI
10.1038/41319
OpenAlex
W1627711548
Semantic Scholar
c9e7c2477f830a1651ba337fbca2c5f17282e752
Cited by
478
References
47
Citations by year
2026: 2 · 2025: 3 · 2024: 5 · 2023: 7 · 2022: 11 · 2021: 18 · 2020: 29 · 2019: 12 · 2018: 6 · 2017: 19 · 2016: 13 · 2015: 16 · 2014: 22 · 2013: 20 · 2012: 29
FWCI
31.73
Type
journal article
Language
en
Open access
closed
Licence
Locations
  • Nature (publishedVersion)
  • PubMed (publishedVersion)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DigitalGeorgetown (Georgetown University Library) (submittedVersion)
Topics
  • Social Sciences › Psychology › Experimental and Cognitive Psychology › Cognitive Abilities and Testing
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic Associations and Epidemiology
  • Social Sciences › Sociology and Political Science › Intergenerational and Educational Inequality Studies
Keywords
shared environment, maternal effects, family environment, twins reared apart
MeSH terms
Adolescent, Adult, Aging, Child, Environment, Embryonic and Fetal Development, Humans, Intelligence, Models, Genetic, Twins, Models, Statistical

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