Emotion musical prosody for robotic groups and entitativity

Research in human-robot interaction has focused on the relationship between a single robot and a single human participant. Only limited research has addressed the contrasting dynamic when humans interact with a group of robots. This dynamic adds additional human-robot interaction considerations, such as the level of entitativity, which is the identification of a group as a single entity as opposed to a collection of individuals. This paper proposes that emotional music prosody can play a key role in improving the interaction between humans and groups of robots by modifying the level of entitativity. Musical prosody refers to the use of pitch, rhythm and timbre features derived from language, but used without semantic meaning.We conducted a between-group experiment, presenting to subjects a group of industrial robotic arms performing a task either without sound, with the same emotional musical prosody voice for each robot, or with contrasting voices for different robots. We were able to show with significant results that the use of musical prosody improved likeability and trust over soundless gestures for groups of robots. We also demonstrate that, through subtle variations, prosody is able to alter the level of entitativity perceived by external observers. Finally, our results indicate a complex relationship between entitativity and common HRI metrics with higher levels of entitativity leading to improved performance, contradicting past literature.