Behavior Genetics

, Volume 40, Issue 2, pp 135–145 | Cite as

Genetic Covariation Between Brain Volumes and IQ, Reading Performance, and Processing Speed

  • Rebecca S. BetjemannEmail author
  • Erin Phinney Johnson
  • Holly Barnard
  • Richard Boada
  • Christopher M. Filley
  • Pauline A. Filipek
  • Erik G. Willcutt
  • John C. DeFries
  • Bruce F. Pennington
Original Research


Although there has been much interest in the relation between brain size and cognition, few studies have investigated this relation within a genetic framework and fewer still in non-adult samples. We analyzed the genetic and environmental covariance between structural MRI data from four brain regions (total brain volume, neocortex, white matter, and prefrontal cortex), and four cognitive measures (verbal IQ (VIQ), performance IQ (PIQ), reading ability, and processing speed), in a sample of 41 MZ twin pairs and 30 same-sex DZ twin pairs (mean age at cognitive test = 11.4 years; mean age at scan = 15.4 years). Multivariate Cholesky decompositions were performed with each brain volume measure entered first, followed by the four cognitive measures. Consistent with previous research, each brain and cognitive measure was found to be significantly heritable. The novel finding was the significant genetic but not environmental covariance between brain volumes and cognitive measures. Specifically, PIQ shared significant common genetic variance with all four measures of brain volume (r g = .58–.82). In contrast, VIQ shared significant genetic influence with neocortex volume only (r g = .58). Processing speed was significant with total brain volume (r g = .79), neocortex (r g = .64), and white matter (r g = .89), but not prefrontal cortex. The only brain measure to share genetic influence with reading was total brain volume (r g = .32), which also shared genetic influences with processing speed.


Twin design MRI Brain volume Intelligence Processing speed Reading 



Initial work on this paper was done when R. Betjemann was a postdoctoral trainee at the Institute for Behavioral Genetics, University of Colorado, Boulder, CO. This training was funded by NIMH training grant T32 MH016880-25. This project was also funded by NIH grant HD027802 to the Colorado Learning Disabilities Research Center, of which B. Pennington, J. DeFries, and E. Willcutt are Co-PIs.


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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Rebecca S. Betjemann
    • 1
    Email author
  • Erin Phinney Johnson
    • 2
    • 7
  • Holly Barnard
    • 2
    • 8
  • Richard Boada
    • 2
    • 3
  • Christopher M. Filley
    • 3
    • 4
  • Pauline A. Filipek
    • 5
  • Erik G. Willcutt
    • 6
  • John C. DeFries
    • 6
  • Bruce F. Pennington
    • 2
  1. 1.Department of Psychology, D-12Regis UniversityDenverUSA
  2. 2.University of DenverDenverUSA
  3. 3.University of Colorado Denver School of MedicineDenverUSA
  4. 4.Denver Veterans Affairs Medical CenterDenverUSA
  5. 5.University of Texas Health Science Center at HoustonHoustonUSA
  6. 6.University of ColoradoBoulderUSA
  7. 7.Waterford Research InstituteSalt Lake CityUSA
  8. 8.Neuropsychiatric InstituteUniversity of IllinoisChicagoUSA

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