Developmental Dyslexia: Past, Present and Future

A discrepancy between reading performance and intelligence is generally held to be a defining characteristic of developmental dyslexia. However, intelligence appears not to be an important factor in distinguishing between the reading performance of different groups of poor readers. Some dyslexia researchers have interpreted this null finding as seriously questioning the existence of dyslexia as a disorder independent of general poor reading. I argue that the anti-discrepancy theorists make three conflations of separate issues: research on the cause of poor reading versus research on the cause of dyslexia; phonological deficit as cause of dyslexia versus symptom of dyslexia; research on the causes of dyslexia versus research on the diagnosis or remediation of dyslexia. Once these issues are teased apart, not only does the apparent dilemma disappear, but a new and fruitful research perspective is suggested. Insights arising from this wider research perspective should transform our understanding of the underlying cause(s) of dyslexia, inform the development of earlier and better methods of screening and remediation and contribute significantly to the understanding of human cognitive development.