When there is a lull in conversation, many people feel awkward and make sounds, such as "ummm" (a vocal filler), or stroke their chins or other parts of their bodies (a bodily filler). These fillers suggest the intent to recommence and continue the conversation. Thus, the purpose of conversation is to facilitate the sharing of beneficial information as well as a comfortable moment with an interlocutor. In this manner, a robot intended to help foster a comfortable or relaxing conversational atmosphere through interaction with a user (e.g., therapeutic robots) needs to be designed to convey such a cooperative demeanor to its human interlocutor. In this study, we analyze the effects of a robot's vocal and bodily fillers during awkward silences between turns in conversations with humans. The results of our study show that people feel awkward during silences, even when in conversation with a robot, and that the robot's conversational fillers help mitigate awkwardness and express a cooperative attitude in verbal interactions with people. Our experiments also revealed that subjects who were less socially adept reported feeling that their robot interlocutor was more sincere than its human counterpart.

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