Paradoxes in the definition of dyslexia

Abstract

The definition and explanation of dyslexia have long been problematic. A causal modelling framework involving three levels of description—behavioural, cognitive and biological—can solve some seemingly intractable problems and confusions. Dyslexia can be defined as a neuro-developmental disorder with a biological origin and behavioural signs which extend far beyond problems with written language. At the cognitive level, putative causes of the behavioural signs and symptoms of the condition can be specified. These hypothetical deficits are subject to controversy, but serve as a basis for testable predictions at both the behavioural and biological levels. At all three levels, interactions with cultural influences occur. These influences have a major impact on the clinical manifestation of dyslexia, the handicap experienced by the sufferer, and the possibilities for remediation. When all these factors are considered together, paradoxes disappear and a satisfactory definition of dyslexia can be achieved. Copyright © 1999 John Wiley & Sons, Ltd