Measuring Communication Participation to Initiate Conversation in Human–Robot Interaction

Consider a situation where a robot initiates a conversation with a person. What is the appropriate timing for such an action? Where is a good position from which to make the initial greeting? In this study, we analyze human interactions and establish a model for a natural way of initiating conversation. Our model mainly involves the participation state and spatial formation. When a person prepares to participate in a conversation and a particular spatial formation occurs, he/she feels that he/she is participating in the conversation; once he/she perceives his/her participation, he/she maintains particular spatial formations. Theories have addressed human communication related to these concepts, but they have only covered situations after people start to talk. In this research, we created a participation state model for measuring communication participation and provided a clear set of guidelines for how to structure a robot’s behavior to start and maintain a conversation based on the model. Our model precisely describes the constraints and expected behaviors for the phase of initiating conversation. We implemented our proposed model in a humanoid robot and conducted both a system evaluation and a user evaluation in a shop scenario experiment. It was shown that good recognition accuracy of interaction state in a conversation was achieved with our proposed model, and the robot implemented with our proposed model was evaluated as best in terms of appropriateness of behaviors and interaction efficiency compared with other two alternative conditions.