PubMed1999
There has been a longstanding controversy about the existence, nature, and differentiation of developmental apraxia of speech (DAS), leading to numerous investigations of characteristics that define this articulatory disorder. An analysis of substitutions relative to target sounds led Thoonen, Maassen, Gabreëls, and Schreuder (1994) to conclude that children with DAS show a pattern of feature retention in their error productions that contrasted with that of children with normal articulation. This pattern, in which place of articulation was retained in the substituted sound less frequently than manner of production or voicing, was considered by Thoonen et al. to be of diagnostic significance. The current research re-examines this claim by comparing the retention patterns obtained by Thoonen et al. for children suspected of having DAS to patterns for children suspected of having a phonological disorder. An examination of substitutions used by 20 children who were diagnosed with and treated for phonological disorders demonstrated the same pattern of feature retention that was described for children with DAS. The results of this study showed that voicing is maintained most frequently; manner of production is the next most retained feature; and place of articulation is the feature that is retained least often when a substitute is used for a sound that isn't produced correctly. In a second analysis, this pattern of feature retention was compared to children's phonological knowledge as indexed by percent correct underlying representation (PCUR). Contrary to the findings of Thoonen et al., however, the present work found an inverse relationship between retention of place and phonological knowledge. Children with greater phonological knowledge retained place less often than children with more limited phonetic inventories. These patterns of feature retention may be representative of specific development sequences that occur during phonological acquisition.