Effects of visual information on intelligibility of open and closed class words in predictable sentences produced by speakers with dysarthria.

This study examined the independent and interactive effects of visual information and linguistic class of words on intelligibility of dysarthric speech. Seven speakers with dysarthria participated in the study, along with 224 listeners who transcribed speech samples in audiovisual (AV) or audio-only (AO) listening conditions. Orthographic transcriptions from listeners were scored for the number of words identified correctly. Correctly identified words were then coded into two linguistic classes, open and closed. Results showed that across all speakers and listeners, the AV presentation mode resulted in significantly higher intelligibility scores than the AO mode. However, the difference was significant for only three of seven individual speakers. Results also showed that across all speakers and listeners, closed class words were more intelligible than open class words. The difference between linguistic classes was significant for six of seven individual speakers. The interaction between linguistic class and mode of presentation was not significant, indicating that the margin of benefit for closed class words was consistent across presentation modalities.