Intelligibility of dysarthric speech: perceptions of speakers and listeners

Background: Many factors influence listener perception of dysarthric speech. Final consensus on the role of gender and listener experience is still to be reached. The speaker's perception of his/her speech has largely been ignored. Aims: (1) To compare speaker and listener perception of the intelligibility of dysarthric speech; (2) to explore the role of gender and listener experience in speech perception; and (3) to examine the relationship between speaker perceptions of intelligibility and formal clinical intelligibility ratings. Methods Procedures: Study 1 examines listener perception of intelligibility of dysarthric speech. Twenty people with acquired dysarthria, ten speech language therapists (SLTs) and 20 naive listeners heard audio recordings of dysarthric speech and used direct magnitude estimation (DME) to rate perceptions of speech intelligibility. Differences in perception across gender and listener experience (SLTs versus naive listeners) were examined. Study 2 tackles the speaker's perception of his/her own speech intelligibility. Using the same groups of participants and DME, speakers rated their own speech intelligibility. SLTs and naive listeners then rated their perception of the speakers' intelligibility. Differences in perceptions between speakers and listeners were compared. Further analysis examined differences across gender and listener experience. Finally, ratings of speakers' perception of their own intelligibility were compared with intelligibility scores on the Assessment of Intelligibility of Dysarthric Speech (ASSIDS) (1981). Outcomes Results: Study 1 showed no statistically significant differences in perception of intelligibility across the three listener groups, although results suggest that speakers rate perceptions of intelligibility differently to SLTs and naive listeners. Despite some individual differences in ratings between speakers and listeners in Study 2, overall there are no significant group differences and methodological limitations to this section of the study are highlighted. In Studies 1 and 2 there are no statistically significant differences across gender and listener experience, although SLTs are less consistent in their ratings of speech when compared with naive listeners. There is no statistically significant relationship between formal intelligibility assessment scores and the speakers' perception of intelligibility. Conclusions: This study contributes to an understanding of perceptions of dysarthric speech. The lack of gender differences in listener perception supports earlier findings in other areas of SLT. The strong relationship between SLT and naive listeners' perceptions suggests that SLTs are not more critical of dysarthric speech. The discrepancy between formal assessment measures and speakers' perceptions of intelligibility has implications for clinical practice. The need for further research in the area is highlighted.