clinical linguistics & phonetics, 2001 , vol. 15, no. 1 & 2, 145±150 Coarticulation within and between syllables by children with developmental apraxia of speech BEN MAASSEN², LIAN NIJLAND² and SJOEKE VAN DER MEULEN ²Child Neurology Centre/Medical Psychology, University Medical Centre Nijmegen, the Netherlands Dept. of Phoniatrics, University Medical Centre Utrecht, the Netherlands Keywords : developmental apraxia of speech (DAS), acoustic analysis, coarticulation, diŒerential diagnosis. Introduction Developmental apraxia of speech (DAS ) is a speech disorder that consists of the inability to produce speech sounds by moving the articulators (tongue, lips, jaw) in the right position, and to correctly sequence sounds into syllables and words. Non- speech actions, like coughing, chewing and swallowing do not necessarily cause diculties. The most salient speech characteristics of children with DAS are: largely unintelligible speech, high consonant error rates, many context-related substitutions, groping, and inconsistency of errors ( Hall et al., 1993; Thoonen et al., 1996 ). According to recent models the underlying de®cit in DAS must be localized somewhere in the transformation from a phonological representation into an arti- culo-motor programme. In their model of speech production Levelt and Wheeldon (1994 ) postulate a `syllabary’, i.e. a store of articulatory representations of syllables, as the intermediate between the phonology and motor output. Children with DAS seem to have diculties in acquiring and automating the processes of storing and retrieving a speech production plan. In a previous study (Boers et al., 1998; Nijland et al., 1999 ), we compared the coarticulation in utterances produced by children with DAS and normally speaking children. These experiments were based on a series of studies by Nittrouer and colleagues (Nittrouer, 1993; Nittrouer et al., 1996 ). Our study showed that the speech of children with DAS is more variable, and shows larger coarticulation eŒects between and within syllables than the speech of normally speaking children. The aim of the present study is to further test the `syllabary’ hypothesis, by manipulating the syllable boundary in the speech material, in otherwise identical Address correspondence to: Ben Maassen, Child Neurology Centre/Medical Psychology, University Medical Centre Nijmegen, 954 IKNC, PO Box 9101, 6500 HB Nijmegen, the Netherlands. e-mail: b.maassen@cksiknc.azn.nl Clinical Linguistics & Phonetics ISSN 0269-9206 print/ISSN 1464-5076 online Ñ 2001 Taylor & Francis Ltd http://www.tandf.co.uk/journals