Signals of Communicative Intent Enhance the Impact of Emotional Messages from Human Speakers, While Effects for Robots are Attenuated

Abstract

The present work investigated humans’ responses to robots’ verbal emotional expressions. To this end, the interplay of agent characteristics and signals of communicative intent on emotional word processing was examined. In two behavioral studies (N1 = 36, N2 = 72), participants watched short videos featuring different agents (humans, androids, and humanoid robots) alongside the auditory presentation of single words of varying valence (negative, neutral, and positive). In the communicative condition, the agent signaled communicative intent by looking at the participant while speaking; in the non-communicative condition, the audio played while the agent remained passive with eyes and mouth closed. After each video, participants rated the valence and arousal of the presented word. The results of both studies revealed a consistent pattern, with differences in emotional word processing based on agent type: For human agents, signals of communicative intent enhanced the emotional impact (arousal dimension) of emotional words. In contrast, for android and humanoid robot agents, the corresponding effects were smaller and statistically non-significant, indicating a relatively lower perceived relevance of direct emotional speech from robots. For all agents, the emotional meaning (valence dimension) of words was robustly conveyed without being affected by the communication manipulation. Further analyses identified the dimension of perceived animacy as a basis for the observed arousal effects. In line with theories that emphasize contextual influences on language processing, our results highlight the role of mind attribution and perceived relevance for emotional language processing in human–robot interaction.