Subtypes of developmental dyslexia

• Main Author: Wybrow, Dean P.
• Published: University of Essex 2014
• Subjects: 616.85
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654953

This thesis is an examination of the idea that dyslexia is a heterogeneous condition and can be characterised by distinct subtypes. The thesis contains four studies conducted on a sample of 41 dyslexic children and around 300 normally reading children. The first three are concerned with the theory that the dual route model of reading applies to developing as well as adult reading. Study One used a regression outlier approach to compare children's nonword reading and irregular word reading and found that roughly equal incidence of surface and phonologica l dyslexia can be found in children. Study Two found, via path analysis of component reading tasks in normal readers, that a particular well-used reading test is inappropriate for use in some studies of surface dyslexia, and Study Three showed, via analysis of predicted word reading ability compared to age, that the dual route model is capable of predicting children's reading performance. Study Four was an investigation of the hypothesis that some dyslexic children have naming speed deficits rather than phonological deficits and the further hypothesis that surface dyslexia and naming speed dyslexia are two manifestations of the same condition. Use of the regression-outlier approach to compare naming speed, nonword reading and irregular word reading found limited support for these hypotheses. The thesis shows that the dual route theory is applicable to developing reading and that dyslexia is characterised by heterogeneity. Future research should bear in mind the diverse nature of dyslexics and attempt to explain this diversity.