Developmental dyslexia is a disorder which affects the acquisition of basic reading and spelling skills in childhood. Originally published in 1986 and reissued here with a new preface, adopting a cognitive approach to the problem, the author bases his discussion on the assumption that the mental system underlying reading competence can be represented as a set of information processors and that these components can be investigated by an application of the experimental methods of cognitive psychology. He presents a particular model of the cognitive system underlying reading competence and describes the practicalities of setting up an appropriate experimental procedure on a microprocessor.

The application of the model and procedure is illustrated by empirical studies of formally competent readers aged about 11 years and by individual analyses of a series of adolescent and young adult dyslexic cases. The results are presented in the form of ‘cognitive descriptions’ of each individual, which specify the status and functioning of each of the components of his/her information processing system. The analyses demonstrate the existence of differences of cognitive functioning among the dyslexic subjects. As the author points out, these do not fall into clearly demarcated sub-types of the kind postulated in recent discussions of acquired dyslexia but appear rather to reflect the possibility that the different processing domains can be independently affected to varying degrees.