Towards a standardised assessment procedure for developmental apraxia of speech

This study addresses the assessment of developmental apraxia of speech (DAS) in children. For this, 11 children with a clear diagnosis of DAS were selected, based on documented speech history and perceptual evaluation of speech. The children with DAS, as well as 11 normal-speaking children, produced singleton real word and nonsense word imitations elicited in a standardised way. Phonetic transcriptions were analysed and errors in consonants classified. The results showed, firstly, that the children with DAS produced similar types of consonant errors as has been reported in the literature, which corroborates the method of elicitation as a valid procedure to assess relevant speech symptoms of DAS. Secondly, a large quantitative difference between children with DAS and normal-speaking children was found, in that children with DAS produced an overall higher rate of singleton consonant errors (substitutions, omissions, distortions) and cluster errors (cluster reductions) than the normal-speaking children. For the DAS group, the substitution-rate, particularly in real words (as opposed to nonsense words), was significantly correlated with severity as rated by two speech and language pathologists. This suggests that substitution-rate yields an adequate measure of severity of DAS. Thirdly, a qualitative difference between both subject groups emerged. Children with DAS did not benefit from the lexical status of the utterance (real versus nonsense word) to the same extent as normal-speaking children. Based on these findings the nature of the underlying deficits in speech production in DAS is discussed.