Effects of word position and stress on onset cluster production : evidence from typical development, specific language impairment and dyslexia

Children with Specific Language Impairment (SLI) and dyslexia have phonological deficits that are claimed to cause their language and literacy impairments and to be responsible for the overlap between the two disorders. Little is known, however, about the phonological grammar of children with SLI and dyslexia, and indeed whether they show differences in phonological development. We designed a non-word repetition task to investigate the impact of word-position and stress on the production accuracy of onset clusters. We compared the performance of children with SLI+dyslexia, SLI-only and Dyslexia-only (mean age 11), and three groups of typically developing children (aged 5, 7 and 9). Analysis of cluster production accuracy revealed that all three clinical groups made significantly more errors on word-medial clusters compared to word-initial clusters. Unstressed clusters were more difficult than stressed clusters for the two dyslexic groups but not the SLI-only group. None of the groups of typically developing children showed an effect of word position or stress on cluster accuracy. However, all groups created new clusters significantly more frequently in initial than medial positions. These results indicate a difference in phonological grammar in children with SLI and dyslexia that could potentially shed light on the relationship between the two disorders. Furthermore, they indicate that structural position and stress are developmentally independent elements in phonological representations