title: Heritability of word recognition in middle-aged men varies as a function of parental education.
abstract: Although it is of lifelong importance, reading ability is studied primarily in children and adolescents. We examined variation in word recognition in 347 middle-aged male twin pairs. Overall heritability (a2) was 0.45, and shared environmental influences (c2) were 0.28. However, parental education moderated heritability such that a2 was 0.21 at the lowest parental education level and 0.69 at the highest level; c2 was 0.52 and 0.00, respectively. This constitutes a parental education x environment interaction. The higher heritability was due to a decrease in the magnitude of shared environmental factors, rather than an increase in the magnitude of genetic factors. Other cognitive studies have reported gene x environment interactions, but patterns may differ as a function of age or specific cognitive abilities. Our results suggest that shared environmental factors in families with low parental education have long-lasting effects on word recognition ability, well beyond any critical period for developing reading proficiency.
authors.affiliation: Department of Psychiatry, Institute of Behavioral Genomics, University of California, San Diego, La Jolla, CA 92093-0603, USA. wkremen@ucsd.edu
authors.forename: William S
authors.initials: WS
authors.lastname: Kremen
authors.forename: Kristen C
authors.initials: KC
authors.lastname: Jacobson
authors.forename: Hong
authors.initials: H
authors.lastname: Xian
authors.forename: Seth A
authors.initials: SA
authors.lastname: Eisen
authors.forename: Brian
authors.initials: B
authors.lastname: Waterman
authors.forename: Rosemary
authors.initials: R
authors.lastname: Toomey
authors.forename: Michael C
authors.initials: MC
authors.lastname: Neale
authors.forename: Ming T
authors.initials: MT
authors.lastname: Tsuang
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lyons
mesh_terms: D003071:Cognition; D004410:Dyslexia / Q000235:genetics*; D004522:Educational Status; D004777:Environment; D006801:Humans; D040582:Inheritance Patterns; D008297:Male; D008875:Middle Aged; D010287:Parent-Child Relations; D012660:Semantics