Comparison of Intelligibility Measures for Adults With Parkinson's Disease, Adults With Multiple Sclerosis, and Healthy Controls.

Purpose: This study obtained judgments of sentence intelligibility using orthographic transcription for comparison with previously reported intelligibility judgments obtained using a visual analog scale (VAS) for individuals with Parkinson's disease and multiple sclerosis and healthy controls (K. Tjaden, J. E. Sussman, & G. E. Wilding, 2014).

Method: Speakers read Harvard sentences in habitual, clear, loud, and slow conditions. Sentence stimuli were equated for peak intensity and mixed with multitalker babble. A total of 50 listeners orthographically transcribed sentences. Procedures were identical to those for a VAS reported in Tjaden, Sussman, and Wilding (2014).

Results: The percent correct scores from transcription were significantly higher in magnitude than the VAS scores. Multivariate linear modeling indicated that the pattern of findings for transcription and VAS was virtually the same with respect to differences among groups and speaking conditions. Correlation analyses further indicated a moderately strong, positive relationship between the two metrics. The majority of these correlations were significant. Last, intrajudge and interjudge listener reliability metrics for the two intelligibility tasks were comparable.

Conclusion: Results suggest that there may be instances when the less time-consuming VAS task may be a viable substitute for an orthographic transcription task when documenting intelligibility in mild dysarthria.