Speech Output Disorders
University of Nijmegen, The Netherlands
The jury is still out on whether speech output or articulation disorders form part of the diagnostic entity specific language impairment. According to Rapin and Allen (1987), developmental apraxia of speech (their term: verbal dyspraxia) forms one cluster in the classification of SLI. They seem to apply the label SLI to all children who attend language units provided they have no other major developmental problems than in the domain of verbal communication skills. In contrast, De Jong (1999) tended to reserve the label SLI for the subgroup of grammatical SLI. The grammatical subtype of SLI is characterized by lacking or inadequate use of morphological and subject–verb agreement rules. Because of this ambiguity, and because speech disorders comprise a separate diagnostic entity, the acronym SLI is used in the sense of speech-language impairment. In the present study, the speech output of a rather heterogeneous group of children with speech-language impairment, receiving special education, is compared to children with unambiguous speech output disorders: dysartria and developmental apraxia of speech (DAS).
The speech production model that is used as a reference in the studies presented here is the model of Levelt (1989). This model comprises routines for phonological encoding and articulation, covering the processes that