The aim of this study was to enhance our insight into the underlying deficit in developmental apraxia of speech (DAS). In particular, the involvement of planning and/or programming of speech movements in context was tested by analysing coarticulatory cohesion. For this purpose, second formant frequency measurements were conducted in repetitions of nonsense utterances ([[symbol: see text]] C = /s,x,b,d/; V = /i.a.u/), and compared across nine children with DAS, six normally speaking (NS) children and six adult women. The results showed both intra- and intersyllabic anticipatory coarticulation in NS children and adult women, in which the intersyllabic coarticulation was stronger in NS children than in adult women. The children with DAS showed more variability as compared to NS children, made, on average, less distinction between the vowels, and showed individually idiosyncratic coarticulation patterns. These results are discussed in the light of a delay as well as a deviance of speech development in children with DAS.

In this study the hypothesis of motor programming involvement in developmental apraxia of speech (DAS) was investigated by studying articulatory compensation. Five children with DAS and 5 normally speaking children (age 5;0 [years;months] to 6;10), and 6 adult women produced utterances in a normal speaking condition and in a bite-block condition in which the mandible was kept in a fixed position. Throughout the utterances, the course of the second formant was used to determine articulatory compensation and the effect of the bite block on anticipatory coarticulation. Results showed that the bite-block condition in normally speaking children, like in adult women, did not affect the extent of anticipatory coarticulation. In the speech of children with DAS, the bite block had large effects on coarticulatory patterns and on vowel quality, which, contrary to expectations, had improved. These results are interpreted as a clear demonstration of deficient motor programming in DAS.

The aim of the present study was to investigate whether children with developmental apraxia of speech (DAS) show a deficit in planning syllables in speech production. Six children with DAS and six normally speaking (NS) children produced high- and low-frequency of occurrence syllable utterances, in which the syllable structure was systematically manipulated in an otherwise unchanging phoneme sequence. Anticipatory coarticulation, using second formant trajectories, and durational structure were analysed. The results showed stronger coarticulation in the children with DAS when compared to the normally speaking children. but in contrast to our expectations, in neither group was a systematic effect of syllable structure on the second format trajectory found. Effects of syllable structure did emerge for durational structure in that durational adjustments were found in the segments of the second syllable. These adjustments were less systematic in children with DAS when compared to normally speaking children. Furthermore, at the prosodic level, normally speaking children showed metrical contrasts that were not realized by the children with DAS. The latter results are interpreted as evidence for a problem in the planning of syllables in speech production of children with DAS, in particular concerning prosodic aspects, which is discussed in relation to the automation of speech production.

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