chapter  25
Phonemic Integrity and Contrastiveness in Developmental Apraxia of Speech
WithHarvey M. Sussman, Thomas P. Marquardt, Jadine Doyle, Heather Knapp
Pages 16

The speech and language deficits of children diagnosed with Developmental Apraxia of Speech (DAS) have been found to span three levels of language structure: input processing, organizational processing, and output processing (Shriberg, Aram, & Kwiatkowski, 1997). The goal of our research program in DAS is to uncover an underlying core deficit that can parsimoniously account for much of the varied behavioral symptomatology of this disorder. Our initial working hypothesis is that DAS primarily involves an impoverishment in the neural representation, and hence functional operation, of phonological categories. Most researchers agree that DAS is a neurologically based disorder, but to date, documented neurological hard signs are not readily evident. In our view, DAS is a developmental neural dysmorphology involving brain tissue that, in the normal brain, subserves the formation of phonemically structured equivalence classes that function as the basic building blocks of a child’s emerging phonological system. Without a well-formed neural representation of the contrastive segmental entities of a language’s sound system, acquisition of normal articulation, morphology, prosody, and syntactic structure can be severely compromised. By focusing our inquiry on the higher order linguistic abstraction of the phonetic category, we can (a) utilize experimentally matched studies investigating categorical integrity for both speech production and perception, and (b) investigate a language entity (the phonetic category) that lies at the core of the organizational level of language structure. The production and perception studies presented next should be viewed primarily as a work in progress, as to date our DAS participant population is relatively small, precluding statistical analysis.