Filled Pauses as a Special Case of Automatic Speech Behaviors and the Effect of Parkinson's Disease

Abstract

Purpose In Parkinson's disease (PD), there are significant changes in the basal ganglia, a structure known to be important for controlling automatic responses to cues. Changes to the basal ganglia in PD impair an individual's ability to trigger a behavior in response to cues, but more so in response to internal cues more than external ones. Filled pauses are considered a subconscious or automatic speech response to an internal cue that there are difficulties with ongoing communication. Typical speakers use filled pauses (such as uh or um) to mark silent pauses. The purpose of this study was to examine how automatic speech responses are impacted in PD by looking at filled and silent pausing behaviors, extending our understanding of the role of the basal ganglia in automatic behaviors. We hypothesized that individuals with PD would use fewer filled pauses and longer silent pauses. We also hypothesized that longer pauses would be more likely to be marked with filled pauses and that this relationship would be weaker in speakers with PD. Method Speech samples were collected via a story-retelling task from 15 individuals with PD and 18 age-matched controls. Duration and frequency of filled and silent pauses were measured using spectrographic analysis. Number and duration of marked silent pauses (those consecutive with 1 or more filled pauses) were measured. The t tests and analyses of variance were used to test our hypotheses. Results There was no significant difference in the number of silent pauses between groups, but the duration of silent pauses was significantly greater for individuals with PD. Despite this, individuals with PD produced significantly fewer filled pauses and fewer marked silent pauses. For both groups, longer silent pauses were more likely to be marked by filled pauses, but individuals with PD marked a smaller percentage of silent pauses at longer durations than controls. Conclusions Producing fewer marked silent pauses, coupled with longer silent pauses, reduces natural cues to discourse and puts people with PD at greater risk of sounding unnatural and losing their communicative turn. These results suggest that automatic responses regarding speech production difficulties are impaired by PD. This interpretation fits with nonspeech literature where automatic responses have been demonstrated to be impaired in PD.