Comparison of intelligibility measures for adults with Parkinson's disease, Multiple Sclerosis and healthy controls
Stipancic, Kaila L.
MetadataShow full item record
Purpose: The current study sought to investigate the relationship between two metrics of sentence intelligibility in adults with Parkinson's Disease (PD), Multiple Sclerosis (MS), and healthy controls. An objective measure of intelligibility, orthographic transcription, and a subjective measure of intelligibility, Visual Analog Scaling (VAS), were the two metrics of intelligibility examined. Areas of interest included 1) comparisons of the pattern of intelligibility change in transcription and VAS, 2) strength of the relationship between these two types of intelligibility measures, and 3) differences in intralistener and interlistener reliability between the two metrics. Methods: 78 speakers and the speech samples reported in Tjaden, Sussman, and Wilding (2014) and Kuo, Tjaden, and Sussman (2014) were used in the current study. The pool of 78 speakers consisted of 32 healthy control speakers, 16 speakers with PD, and 30 speakers with MS. Speakers read Harvard Psychoacoustic Sentences in habitual, clear, fast, loud, and slow conditions. In Tjaden et al. (2014) and Kuo et al. (2014), 50 naive listeners used a VAS on a computer to estimate how much of the speaker's message was understood (e.g., from 'didn't understand anything' to 'understand everything'). In the current study, 50 naive listeners heard the same stimuli, but were instructed to type exactly what they heard. Responses were scored to obtain a percentage of key words transcribed correctly for each stimulus. Results from the current study were compared to results from the VAS task studies (Tjaden et al., 2014; Kuo et al., 2014) using descriptive statistics (e.g., mean, standard deviation, etc.), parametric statistics (e.g., multivariate linear model fit to the data in this repeated measured design), correlation analyses (e.g., between the two metrics), and metrics of reliability. Results and Discussion: Results revealed that the pattern of transcription intelligibility scores was very similar to scaled intelligibility derived from VAS. However, transcription scores were higher in magnitude than the VAS scores. In addition, correlation analyses showed the two intelligibility measures were highly correlated. Last, both interlistener and intralistener reliability were marginally higher for the VAS reported in Tjaden et al. (2014) and Kuo et al. (2014) than for the transcription data in the current study. These results suggest that a less time-consuming task, such as the VAS task, may be a viable substitute for a more time-consuming transcription task when documenting intelligibility in a clinical population to obtain an overall metric of severity for tracking disease progression and/or treatment progress.