ABSTRACT
Deficits in reading isolated words accurately and fluently are highly correlated with word-reading deficits in context. These deficits constrain the comprehension of text (Perfetti, 1985; Shankweiler, 1989), and they are often considered to be the hallmark of developmental dyslexia. In 1982, investigators in the Colorado Learning Disabilities Research Center (CLDRC) initiated a study of identical and fraternal twins to advance our understanding of the genetic and environmental etiology of reading disabilities, including isolated word reading and related skills. In 1999, the CLDRC joined an international collaboration with investigators in Australia (Brian Byrne) and Scandinavia (Stefan Samuelsson) on a longitudinal twin study of individual differences in preliteracy and early literacy development beginning in preschool. In this chapter I will provide an overview of some of the methods, major results, and future directions for these two ongoing research programs. I want to emphasize that research in the CLDRC has been and continues to be a highly collaborative effort across our different laboratories. I serve as the Center Director in the Institute for Behavioral Genetics at the University of Colorado. The current coprinciple investigators in the CLDRC include, Brian Byrne (University of New England), Janice Keenan and Bruce Pennington (University of Denver), Shelley Smith (University of Nebraska), and John DeFvies, Sally Wadsworth and Erik Willcutt and Barbava Wise (University of Colorado).
