The Nature and Nurture of High IQ: An Extended Sensitive Period for Intellectual Development

Angela M. Brant, Yuko Munakata, Dorret I. Boomsma, John C. DeFries, Claire M.A. Haworth, Matthew C. Keller, Nicholas G. Martin, Matthew McGue, Stephen A. Petrill, Robert Plomin, Sally J. Wadsworth, Margaret J. Wright, John K. Hewitt

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


IQ predicts many measures of life success, as well as trajectories of brain development. Prolonged cortical thickening observed in individuals with high IQ might reflect an extended period of synaptogenesis and high environmental sensitivity or plasticity. We tested this hypothesis by examining the timing of changes in the magnitude of genetic and environmental influences on IQ as a function of IQ score. We found that individuals with high IQ show high environmental influence on IQ into adolescence (resembling younger children), whereas individuals with low IQ show high heritability of IQ in adolescence (resembling adults), a pattern consistent with an extended sensitive period for intellectual development in more-intelligent individuals. The pattern held across a cross-sectional sample of almost 11,000 twin pairs and a longitudinal sample of twins, biological siblings, and adoptive siblings.

Original languageEnglish (US)
Pages (from-to)1487-1495
Number of pages9
JournalPsychological Science
Issue number8
StatePublished - Aug 2013

Bibliographical note

Funding Information:
This work was supported by the John Templeton Foundation through the Genetics of High Cognitive Ability Consortium (Grant 13575). The opinions expressed in this report are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. Recruitment and data collection for the Colorado Longitudinal Twin Study and the Colorado Adoption Project was funded by National Institutes of Health Grant HD010333. Support obtained for the twin studies of the Genetics of High Cognitive Ability Consortium members is outlined in Haworth et al. (2010) . J. K. Hewitt and Y. Munakata were also supported by National Institute of Mental Health Grant MH079485.


  • behavior genetics
  • cognitive ability
  • cognitive development
  • individual differences
  • intelligence


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