Twin Research and Human Genetics

Articles

Heritability of Verbal and Performance Intelligence in a Pediatric Longitudinal Sample

Inge L.C. van Soelena1 c1, Rachel M. Brouwera2, Marieke van Leeuwena3, René S. Kahna4, Hilleke E. Hulshoff Pola5 and Dorret I. Boomsmaa6

a1 Department of Biological Psychology, VU University Amsterdam, The Netherlands; Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, University Medical Center Utrecht, The Netherlands. ilc.van.soelen@psy.vu.nl

a2 Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, University Medical Center Utrecht, The Netherlands.

a3 Department of Psychosocial Research and Epidemiology, The Netherlands Cancer Insititute, Amsterdam, The Netherlands.

a4 Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, University Medical Center Utrecht, The Netherlands.

a5 Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, University Medical Center Utrecht, The Netherlands.

a6 Department of Biological Psychology, VU University Amsterdam, The Netherlands.

Abstract

The longitudinal stability of IQ is well-documented as is its increasing heritability with age. In a longitudinal twin study, we addressed the question to what extent heritability and stability differ for full scale (FSIQ), verbal (VIQ), and performance IQ (PIQ) in childhood (age 9–11 years), and early adolescence (age 12–14 years). Genetic and environmental influences and correlations over time were evaluated in an extended twin design, including Dutch twins and their siblings. Intelligence was measured by the Wechsler Intelligence Scale for children — Third version (WISC III). Heritability in childhood was 34% for FSIQ, 37% for VIQ, and 64% for PIQ, and increased up to 65%, 51%, and 72% in early adolescence. The influence of common environment decreased between childhood and early adolescence from explaining 43% of the phenotypic variance for FSIQ to 18% and from 42% for VIQ to 26%. For PIQ common environmental influences did not play a role, either in childhood or in early adolescence. The stability in FSIQ and VIQ across the 3-year interval (rp) was .72 for both measures and was explained by genetic and common environmental correlations across time (FSIQ, rg = .96, rc = 1.0; VIQ, rg =.78, rc = 1.0). Stability of PIQ (rp =.56) was lower and was explained by genetic influences (rg = .90). These results confirm the robust findings of increased heritability of general cognitive abilities during the transition from childhood to adolescence. Interestingly, results for PIQ differ from those for FSIQ and VIQ, in that no significant contribution of environment shared by siblings from the same family was detected.

(Received November 16 2010)

(Accepted December 20 2010)

Keywords

  • intelligence quotient (IQ);
  • verbal IQ;
  • performance IQ;
  • childhood;
  • adolescence;
  • longitudinal model;
  • development

Correspondence:

c1 ADDRESS FOR CORRESPONDENCE: Inge L.C. van Soelen, Department of Biological Psychology, VU University, Van der Boechorststraat 1, 1081 BT, Amsterdam, The Netherlands.

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