The relationship between listener comprehension and intelligibility scores for speakers with dysarthria

This study examined the relationship between listener comprehension and intelligibility scores for speakers with mild, moderate, severe, and profound dysarthria. Relationships were examined across all speakers and their listeners when severity effects were statistically controlled, within severity groups, and within individual speakers with dysarthria.

Speech samples were collected from 12 speakers with dysarthria secondary to cerebral palsy. For each speaker, 12 different listeners completed 2 tasks (for a total of 144 listeners): One task involved making orthographic transcriptions, and 1 task involved answering comprehension questions. Transcriptions were scored for the number of words transcribed correctly. Responses to comprehension questions were scored on a 3-point scale according to their accuracy.

Across all speakers, the Pearson product-moment correlation between comprehension and intelligibility scores was nonsignificant when the effects of severity were factored out and residual scores were examined. Within severity groups, the same relationship was significant only for the mild group. Within individual speaker groups, the relationship was nonsignificant for all but 2 speakers with dysarthria. Percentage of correct scores for listener comprehension was descriptively higher than percentage of correct intelligibility scores for all groups.

Findings suggest that transcription intelligibility scores do not accurately reflect listener comprehension scores. Measures of both intelligibility and listener comprehension may provide a more complete description of the information-bearing capability of dysarthric speech than either measure alone.