To Err is Human(-like): Effects of Robot Gesture on Perceived Anthropomorphism and Likability

Previous work has shown that non-verbal behaviors affect anthropomorphic inferences about artificial communicators such as virtual agents or social robots. In an experiment with a humanoid robot we investigated the effects of the robot's hand and arm gestures on the perception of humanlikeness, likability of the robot, shared reality, and future contact intentions after interacting with the robot. For this purpose, the speech-accompanying non-verbal behaviors of the humanoid robot were manipulated in three experimental conditions: (1) no gesture, (2) congruent co-verbal gesture, and (3) incongruent co-verbal gesture. We hypothesized higher ratings on all dependent measures in the two multimodal (i.e., speech and gesture) conditions compared to the unimodal (i.e., speech only) condition. The results confirm our predictions: when the robot used co-verbal gestures during interaction, it was anthropomorphized more, participants perceived it as more likable, reported greater shared reality with it, and showed increased future contact intentions than when the robot gave instructions without gestures. Surprisingly, this effect was particularly pronounced when the robot's gestures were partly incongruent with speech, although this behavior negatively affected the participants' task-related performance. These findings show that communicative non-verbal behaviors displayed by robotic systems affect anthropomorphic perceptions and the mental models humans form of a humanoid robot during interaction.