A perceptual and electropalatographic study of /∫/ in young people with Down's syndrome

Abstract

Speech production in young people with Down's syndrome has been found to be variable and inconsistent. Errors tend to be more in the production of sounds that typically develop later, for example, fricatives and affricates, rather than stops and nasals. It has been suggested that inconsistency in production is a result of a motor speech deficit. Late acquired fricatives such as /s/ and /∫/ are complex articulations, which may require more precise motor programming and may therefore show highly inconsistent productions. Other factors potentially affecting speech production in this population are abnormal palatal structure, hearing loss, and hypotonia. A group of 20 young people with Down's syndrome were recorded using Electropalatography (EPG), reading a wordlist containing the phrase ‘a sheep’. The wordlist contained seven other phrases and was repeated 10 times. Eight typically developing, cognitively matched children and eight adults were also recorded producing the same data set. Articulatory (EPG pattern analysis) and perceptual analyses of the 10 productions of /∫/ were carried out. /∫/ production was found to be inconsistent in the young people with Down's syndrome, with more errors both in the auditory analysis and articulatory analysis than in the typical sample, which may be due to a motor programming or motor control problem. There were a greater number of errors in the EPG analysis than in the perceptual analysis. This suggests that some young people with DS were able to produce perceptually acceptable /∫/ with atypical EPG patterns. The use of typical, adult-modelled /∫/ EPG patterns in therapy may be inappropriate for some children with DS who present with atypical palatal structures.