Peripersonal Space Perception Is Similar When We Interact With Other Humans or With Humanoid Robots.

The peripersonal space is a multisensory interface between the body and the environment, which can be modulated by the presence of objects or other agents. However, how the presence of artificial agents affects the representation of peripersonal space is still poorly understood. We conducted four experiments in which participants had to judge objects' reachability for themselves or for another agent. In Experiment 1, participants performed the reachability task alone. In Experiment 2, participants interacted with another human partner. Experiment 2b was a control condition to test task's physical properties. In Experiment 3, participants performed the task with the humanoid robot iCub, programmed to exhibit motor and social behaviours. The results showed that the extent of the peripersonal space was influenced by the presence of another agent, as participants narrowed their own peripersonal space in a social context, compared to performing the task alone. Furthermore, they perceived their own peripersonal space as larger, compared to the peripersonal space of another human agent (Experiment 2) or humanoid robot (Experiment 3). This suggests that the motor repertoire of a human and a humanoid embodied artificial agent is similarly perceived. The present evidence may open new avenues for space perception in social interactions.