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Parkinson's disease impacts feedback production during verbal communication.

BACKGROUND
Parkinson's disease (PD) leads to changes in verbal communications. The focus of most studies to date has been on speech impairment, which is specifically referred to as dysarthria. Although these studies are crucial to understanding the impact of PD on verbal communication, they do not focus on the features of dialogues between people with PD (PwPD) and other people in communicative contexts.


AIMS
To investigate whether PwPD produce less feedback than typical people during dialogue, thus potentially making it more difficult for them to reach mutual comprehension (i.e., common ground) with their conversational partner.


METHODS & PROCEDURES
A matching task experiment was conducted during which an experimenter described abstract pictures to a participant, who was either a PwPD or a typical participant, so that he or she could organize these pictures in a grid. The participants could produce as much feedback as they liked.


OUTCOMES & RESULTS
PwPD were less likely to produce feedback than typical participants. This effect was mainly driven by two specific types of feedback: acknowledgment tokens and hesitations.


CONCLUSIONS & IMPLICATIONS
The results suggest that PD impacts feedback production. This could decrease the communicative abilities of PwPD in interactive contexts by affecting grounding, that is, the ability to build common ground with others. This paper is one of the first to specifically document the production of feedback markers in PwPD. Future studies should examine the extent to which our results, which were obtained in a controlled dialogue task, may be generalized to daily-life conversions. From a clinical perspective, our study points to the necessity of assessing feedback production, and more generally abilities related to common ground construction and use, during PD progression.


WHAT IS ALREADY KNOWN ON THE SUBJECT
A few studies to date have analyzed conversational interactions between people with Parkinson's disease (PwPD) and others. The main focus is usually on potential difficulties of PwPD and their partners during the interaction and the strategies adopted to "repair" these problems. Another important feature of any interaction is the production of feedback. Feedback production plays a key role in building and using common ground to ensure mutual comprehension between interlocutors. The impact of Parkinson's disease on feedback production has received little attention in the literature to date.


WHAT THIS STUDY ADDS
The purpose of this study was to compare feedback production in a dialogue task (i.e., goal-oriented interaction) in PwPD versus typical controls. Our results revealed that PwPD produced less feedback for their dialogue partners than did typical participants. This effect was mainly driven by two specific types of feedback: acknowledgment tokens and hesitations. This paper is one of the firsts to specifically document the production of feedback markers in PwPD and to illustrate that PwPD and their dialogue partners may require more time and effort to establish common ground.


CLINICAL IMPLICATIONS OF THIS STUDY
Our findings suggest that an appropriate evaluation of feedback production by speech and language therapists, as well the management of potential deficits, would be beneficial. More broadly, we believe that the evaluation and management of PwPD should take into account the theoretical framework used in this study, in particular the role of common ground in communication.