Modeling the Etiology of Individual Differences in Early Reading Development: Evidence for Strong Genetic Influences.

We explored the etiology of individual differences in reading development from post-kindergarten to post-4 ^th grade by analyzing data from 487 twin pairs tested in Colorado. Data from three reading measures and one spelling measure were fit to biometric latent growth curve models, allowing us to extend previous behavioral genetic studies of the etiology of early reading development at specific time points. We found primarily genetic influences on individual differences at post-1 ^st grade for all measures. Genetic influences on variance in growth rates were also found, with evidence of small, nonsignificant, shared environmental influences for two measures. We discuss our results, including their implications for educational policy.