A twin and adoption study of reading achievement: Exploration of shared-environmental and gene–environment-interaction effects

Existing behavior-genetic research implicates substantial influence of heredity and modest influence of shared environment on reading achievement and reading disability. Applying DeFries–Fulker analysis to a combined sample of twins and adoptees (N = 4886, including 266 reading-disabled probands), the present study replicates prior findings of considerable heritability for both reading achievement and reading disability. A simple biometric model adequately described parent and offspring data (combined N = 9430 parents and offspring) across differing types of families present in the sample Analyses yielded a high heritability estimate (around 0.70) and a negligible shared-environmentality estimate for both reading achievement and reading disability. No evidence of gene × environment interaction was found for parental reading ability and parental educational attainment, the two moderators analyzed.

► Twin and adoption study of reading achievement and disability. ► Familial phenotypic correlations were consistent with a simple biometric model. ► Heritability estimates ~ 0.70; shared-environmentality estimates < 0.10. ► Heritability not moderated by parental education or reading achievement.