The similarities between normal readers and developmental and acquired dyslexics

Abstract

Recently several people have suggested strong similarities between the symptoms of acquired and developmental dyslexia. It is an interesting suggestion because it offers us a new way of looking at differences among dyslexic children (always a thorny problem) and also a possible explanation for these children's difficulties. However, the symptoms in question could only be used as a basis for such an explanation if they really were distinctive, that is, did not crop up in normal children at the same reading level. We take two attempts to connect acquired with developmental dyslexia, each involving an adolescent girl who read roughly at the level of a 10-year-old child. One of these two girls (Temple & Marshall, 1983) read in a rather similar way to that of a typical phonological dyslexic. The other (Coltheart et al. 1983) resembled a typical surface dyslexic. Neither study included any comparison with normal children, and so one cannot be certain that there was anything unusual about either girl's reading patterns. We gave the tests used in the two reports just mentioned to 16 normal readers, all reading at the 10-year-level, and we found evidence for all the symptoms described in those reports in normal children as well. The symptoms were not abnormal and cannot be used to explain the two dyslexic children's difficulties. We also found strong and systematic individual differences in our normal group along a “phonological to surface” continuum. So our study does two things. One is show that the reading patterns reported by Temple and Marshall and of Coltheart et al. do not provide an explanation of the causes of these children's reading difficulties. The other is to provide a new way of looking at qualitative differences among normal readers.