A longitudinal study of dyslexic children

A consensus has emerged in recent years that there is an underlying deficit in phonological awareness in many dyslexic children. In an effort to get a clearer picture of how dyslexic children develop, British researchers Margaret J. Snowling, University of York; Neil Defty, University of Durham; and Nata Goulandris, University College/London, studied the development of literacy skills in 20 dyslexic children.

At the beginning of the two-year study, when these 20 children were in the early primary grades, they were matched individually for reading age and IQ with normally developing younger readers and with a comparison group of same-age peers. The dyslexic children did significantly less well than their same-age peers on all the reading, spelling and phonological processing tasks, with the exception of naming pictures (vocabulary). However, their pattern of performance was similar to that of younger children at the same reading level.

During the study, the dyslexic children made slower progress learning to read, and they experienced persistent difficulties in nonword reading, phonological processing and spelling. At the end of the study, these children were compared to a new group of younger readers who matched their reading level. Tests revealed that their reading development was not merely delayed; it had developed differently. After two years, a pattern had emerged: the dyslexic children were worse than younger, normal readers at their same reading level in nonword reading and phonological processing, with a tendency for their spelling to be less phonetic. Many had difficulty with the order of recall in the verbal short-term memory tests as well. On average, however, their oral vocabulary continued to develop normally.

On the basis of previous research and the results of this study, these researchers theorize that dyslexia is not only a delay in reading development but a pattern of deviant processing, primarily on phonological tasks. Even when compared to children reading at the same level, dyslexic readers showed impairments in phonological skills and verbal memory. Although the dyslexic children in this study received extra help in reading and spelling, they continued to develop more slowly.

Snowling et al. point out that their research is limited by the small sample of students that they studied. However, on the basis of cumulative research, they suggest that dyslexic children are delayed in the acquisition of phonological skills in spoken language, and that this delay produces a disorder of written language development. The full impact of the dyslexic children’s difficulties in phonological processing becomes apparent only when you follow their development over time. Although they can learn to read words, dyslexic children continue to have trouble deciphering new words. Thus, even when they have learned to read, most are not able to use their knowledge to automatically add new words to their reading vocabulary. These researchers predict continuing impairments of phonological awareness and verbal short-term memory for these children.


“A Longitudinal Study of Reading Development in Dyslexic Children”, Journal of Educational Psychology, Volume 88, Number 4, December 1996 pp. 653-669.

Published in ERN March/April 1997 Volume 10 Number 2

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