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The heritability of IQ

Author

Listed:
  • B. Devlin

    (University of Pittsburgh School of Medicine
    Carnegie Mellon University)

  • Michael Daniels

    (Carnegie Mellon University)

  • Kathryn Roeder

    (Carnegie Mellon University)

Abstract

IQ heritability, the portion of a population's IQ variability attributable to the effects of genes1, 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 octogenarians2, for instance, suggests that IQ heritability either remains constant through adolescence and adulthood3, or continues to increase with age2. Although the latter hypothesis has recently been endorsed4, 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.

Suggested Citation

  • B. Devlin & Michael Daniels & Kathryn Roeder, 1997. "The heritability of IQ," Nature, Nature, vol. 388(6641), pages 468-471, July.
  • Handle: RePEc:nat:nature:v:388:y:1997:i:6641:d:10.1038_41319
    DOI: 10.1038/41319
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    Citations

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    Cited by:

    1. Lex Borghans & Angela Lee Duckworth & James J. Heckman & Bas ter Weel, 2008. "The Economics and Psychology of Personality Traits," Journal of Human Resources, University of Wisconsin Press, vol. 43(4).
    2. Heckman, James J. & Kautz, Tim, 2012. "Hard evidence on soft skills," Labour Economics, Elsevier, vol. 19(4), pages 451-464.
    3. Henry T Robertson & David B Allison, 2012. "A Novel Generalized Normal Distribution for Human Longevity and other Negatively Skewed Data," PLOS ONE, Public Library of Science, vol. 7(5), pages 1-7, May.
    4. Southwick, Daniel A. & Liu, Zhaoying V. & Baldwin, Chayce & Quirk, Abigail L. & Ungar, Lyle H. & Tsay, Chia-Jung & Duckworth, Angela L., 2023. "The trouble with talent: Semantic ambiguity in the workplace," Organizational Behavior and Human Decision Processes, Elsevier, vol. 174(C).
    5. Napel, Stefan & Schneider, Andrea, 2008. "Intergenerational talent transmission, inequality, and social mobility," Economics Letters, Elsevier, vol. 99(2), pages 405-409, May.
    6. Madsen, Jakob B., 2016. "Barriers to Prosperity: Parasitic and Infectious Diseases, IQ, and Economic Development," World Development, Elsevier, vol. 78(C), pages 172-187.
    7. Gurmeet Singh Sarla, 2019. "Is a Physician Armed with Soft Skills More Successful?," International Journal of Pulmonary & Respiratory Sciences, Juniper Publishers Inc., vol. 4(1), pages 1-3, July.
    8. James Heckman & Tim Kautz, 2013. "Fostering and Measuring Skills: Interventions That Improve Character and Cognition," Working Papers 2013-019, Human Capital and Economic Opportunity Working Group.
    9. Almlund, Mathilde & Duckworth, Angela Lee & Heckman, James & Kautz, Tim, 2011. "Personality Psychology and Economics," Handbook of the Economics of Education, in: Erik Hanushek & Stephen Machin & Ludger Woessmann (ed.), Handbook of the Economics of Education, edition 1, volume 4, chapter 0, pages 1-181, Elsevier.
    10. Florian Wendelspiess Chávez Juárez, 2015. "Intergenerational transmission of education: the relative importance of transmission channels," Latin American Economic Review, Springer;Centro de Investigaciòn y Docencia Económica (CIDE), vol. 24(1), pages 1-44, December.
    11. Anger, Silke, 2011. "The Intergenerational Transmission of Cognitive and Non-Cognitive Skills During Adolescence and Young Adulthood," IZA Discussion Papers 5749, Institute of Labor Economics (IZA).
    12. Christiane Capron & Vetta Atam, 2001. "Comments on “Why Have Children in the 21st Century?”," European Journal of Population, Springer;European Association for Population Studies, vol. 17(1), pages 21-30, March.
    13. Bacolod, Marigee & Blum, Bernardo S. & Rangel, Marcos A. & Strange, William C., 2023. "Learners in cities: Agglomeration and the spatial division of cognition," Regional Science and Urban Economics, Elsevier, vol. 98(C).
    14. Samuel Bowles & Herbert Gintis, 2002. "The Inheritance of Inequality," Journal of Economic Perspectives, American Economic Association, vol. 16(3), pages 3-30, Summer.
    15. Kautz, Tim & Heckman, James J. & Diris, Ron & ter Weel, Bas & Borghans, Lex, 2014. "Fostering and Measuring Skills: Improving Cognitive and Non-Cognitive Skills to Promote Lifetime Success," IZA Discussion Papers 8696, Institute of Labor Economics (IZA).
    16. Björklund, Anders & Jäntti, Markus, 2012. "How important is family background for labor-economic outcomes?," Labour Economics, Elsevier, vol. 19(4), pages 465-474.
    17. Samuel Bowles & Herbert Gintis, 2001. "The Inheritance of Economic Status: Education, Class, and Genetics," Working Papers 01-01-005, Santa Fe Institute.
    18. Martin Kolk & Kieron J. Barclay, 2017. "Cognitive ability and fertility amongst Swedish men: evidence from 18 cohorts of military conscription," MPIDR Working Papers WP-2017-020, Max Planck Institute for Demographic Research, Rostock, Germany.

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