Vowel Intelligibility in Children With and Without Dysarthria: An Exploratory Study

Children with dysarthria due to cerebral palsy (CP) present with decreased vowel space area and reduced word intelligibility. Although a robust relationship exists between vowel space and word intelligibility, little is known about the intelligibility of vowels in this population. This exploratory study investigated the intelligibility of American-English vowels produced by children with dysarthria and typically-developing children (TD). Three CP and five TD repeated words with contrastive vowels /i-ɪ/,/æ-ɛ/,/ɑ-ʌ/,/o-u/ produced by a native American-English adult. Adult listeners transcribed the utterances orthographically and rated their ease of understanding. Overall, CP presented with less-intelligible vowels than TD. For CP, a trend was found with the lowest intelligibility for /ɑ/ (CP=7%,TD=66%), /ɪ/ (CP=30%,TD=82%), and /ʌ/ (CP=38%,TD=99%), and more heterogeneous vowel confusions; however, intelligibility differences between vowels did not reach statistical significance. Clinical implications include that, unless further studies show vowel-specific effects, treatment targeting the entire vowel system may be warranted for increasing intelligibility