Entrainment, a physical phenomenon in which one individual's expressed information synchronizes with another's and vice versa, can be observed between two communicators who are interacting naturally. In this study, we focused on the "rate of utterances" as communicators' expressed information and then conducted an experiment to observe whether or not entrainment naturally occurs in the rate of utterances in speech dialogs between users and an auto response system. Specifically, participants were asked to read given dialog scripts with an auto response system that replied with different rates of utterances. The results revealed that 1) when the system's rate of utterances increased, the participants produced faster rates of utterances, 2) when the system's rates decreased, participants spoke at slower rates. These results suggest entrainment in the rate of utterances naturally occurs in speech dialogs between participants and an auto response system.

entrainment, speech interface, rate of utterances