Defining dyslexia as a developmental language disorder

Dyslexia has recently been defined as a developmental language disorder (Catts, 1989a; Kamhi & Catts, 1989). In this article, the language basis of dyslexia and the current research that supports and extends it are reviewed. Research continues to indicate that phonological processing deficits lie at the core of dyslexia. However, recent evidence also suggests that these deficits may underlie the difficulties of many poor readers who do not meet the traditional definitions of dyslexia (i.e., low achievers). Rather than collapse dyslexics and low achievers into a single diagnostic category, it is argued that these groups or groups like them may be differentiated on the basis of higher-level language abilities. The role of higher-level language functioning and phonological processing in reading is further considered in an expanded view of the language basis of reading disabilities. The implications this view has for the early identification and remediation of reading disabilities are also presented.