Shaping unbalanced multi-party interactions through adaptive robot backchannels

Non-verbal cues used in human communication have shown to be efficient in shaping speaking interactions. When applied to virtual agents or social robots, results imply that a similar effect is expected in dyad settings. In this study, we explore how encouraging, vocal and non-vocal, backchannels can stimulate speaking participation in a game-based multi-party interaction, where unbalanced contribution is expected. We design the study using a social robot, taking part in a language game with native speakers and language learners, to evaluate how an adaptive generation of backchannels, that targets the least speaking participant to encourage more speaking contribution, affects the group and individual participant's behavior. We report results from experiments with 30 subjects divided in pairs assigned to the adaptive (encouraging) and (neutral) control condition. Our results show that the speaking participation of the least active speaker increases significantly when the robot uses an adaptive backchanneling strategy. At the same time, the participation of the more active speaker slightly decreases, which causes the combined speaking time of both participants to be similar between the Control and Experimental conditions. The adaptive strategy further leads to a 50% decrease in the difference in speaker shares between the two participants (indicating a more balanced participation) compared to the Control condition. However, this distribution between speaker ratios is not significantly different from the Control.