Vowel Intelligibility in Children with and Without Dysarthria

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 (AE) vowels produced by children with dysarthria and typically developing children (TD). Three CP and five TD repeated words with contrastive vowels /i-i/, /æ-ε/, /α-∧/, /o-u/ produced by a native AE 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 /α/ (CP = 7%, TD = 66%), /i/ (CP = 30%, TD = 82%), and /∧/ (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.