The genetics of children's oral reading performance.

Measures of reading achievement and verbal ability have been shown to be heritable. Additionally, recent evidence has been suggestive of a major gene effect on reading disability and for problem reading in a sample of normal readers. We report on the etiology of individual differences in oral reading performance, the Slosson Oral Reading Test (SORT), for which biometrical analyses have not been reported in the literature previously. Oral reading performance was measured in a large population-based sample of twins of the Virginia Twin Study of Adolescent Behavioral Development. Biometrical analyses of the SORT suggested that, in both males and females, 69% of the phenotypic variation was due to heritable influences and 13% of the variation due to shared environmental effects. While the relative importance of genetic and environmental influences is equivalent for males and females, males showed greater phenotypic variability than females.