Developmental dyslexia: a cognitive experimental analysis of phonological, morphemic, and visual impairments

Abstract The results of a cognitive experimental analysis of the reading functions of four developmentally dyslexic subjects are presented. Data are considered on an individual basis in an attempt to specify the primary source of disturbance in each case, and the manner in which the normal course of reading development has been distorted. Subject RO showed an effect on the analytic functioning of the visual processor, which affected speed of non-word reading, but appeared not to have prevented the construction of a normal visual word recognition system. In subject LT a phonological impairment was implicated, and this was associated with a pattern of performance similar to that of adult phonological dyslexics. Subjects GS and SE gave evidence of serial letter-by-letter reading (impaired wholistic function of the visual processor), which produced a pattern not unlike that of adult surface dyslexics (effects of spelling regularity, regularisation errors). The manner in which these impairments might disrupt the development and organisation of visual word recognition is discussed.