Genetic and Environmental Influences on Reading and Language Ability and Disability

Our chapter describes the initially independent development and more recent convergence of two research programs on deficits in reading and related cognitive skills. At the University of Colorado, a multidisciplinary behavioral-genetic study of identical and fraternal twins from the 3rd through 12th grades has been underway since 1982 with continuous funding from the National Institutes of Health (DeFries et al., 1997). At the University of New England in New South Wales, Australia, Brian Byrne and colleagues have been supported by the Australian Research Council to explore the precursors of early reading development through longitudinal studies of children beginning in preschool, prior to formal reading instruction, and subsequently followed through the early grades. Most recently, the Australian and Colorado research programs have converged in an international (including Scandinavia with Stefan Samuelsson) longitudinal preschool twin study of genetic and environmental influences on prereading and early reading development.