Feature analysis of singleton consonant errors in developmental verbal dyspraxia (DVD)

The aim of this study is to quantify diagnostic characteristics related to consonant production of developmental verbal dyspraxia (DVD). For this, a paradigmatic and syntagmatic feature-value analysis of the consonant substitution and omission errors in DVD speech was conducted. Following a three-step procedure, eleven clear cases were selected from a group of 24 children with DVD. The consonants produced in a word and nonsense-word imitation task were phonetically transcribed and transferred to confusion matrices, which allows for a feature and feature-value analysis. The analysis revealed that children with DVD (a) show low percentages of retention for place and manner of articulation and voicing, due to high substitution and omission rates; (b) show a particularly low percentage of retention of place of articulation in words, which, together with error rate, is strongly related to severity of involvement; (c) are inconsistent in their feature realization and feature preference; and (d) show a high syntagmatic error rate. These results form a quantification of diagnostic characteristics. Unexpectedly, however, very few qualitative differences in error pattern were found between children with DVD and a group of 11 age-matched children with normal speech. Thus, although the children with DVD produced higher substitution and omission rates than children with normal speech, the speech profiles of both subject groups are similar. This result stresses the importance of interpreting profiles, not isolated symptoms. The hypothesis to consider DVD as a deficit in the phonological encoding process is discussed.