Characteristics of developmental dyslexia

Abstract

The term dyslexia is applied both to the difficulty a child may experience in learning to read and to reading problems resulting from brain damage in previously normal adults. The present study is concerned with whether the pattern of reading performance of developmental dyslexic boys across different word types resembles any of the patterns observed with acquired dyslexic patients. Single word reading is studied in 32 dyslexic boys, 16 normal readers of equivalent age and 16 younger children of equivalent reading age to the dyslexics. Cluster analysis failed to reveal any difference in pattern of reading performance between dyslexics and younger children of equivalent reading age. Subsequent analysis concentrated on the effect on the reading by dyslexics and reading age controls of material selected so as to explore the importance of a range of variables that have proved to be diagnostic of one or other type of acquired dyslexia. Clear effects of lexicality were noted with non-words being harder to read than words. Words with irregular spelling were harder than regular words, long words somewhat harder than short, and words of late age-of-acquisition were harder than words acquired at an early age. All these effects applied equally to the dyslexics and the reading age control group. There was a weak effect of imageability that was not shown by the reading age controls, while no effect of part-of-speech or word frequency was found in any of the groups. Comparison with the pattern of errors shown by adult developmental dyslexics suggested some similarity with surface dyslexia. However the acquired dyslexics were even more similar to normal children of equivalent reading age.