Invisible body illusion modulates interpersonal space

Interpersonal space (e.g., IPS) refers to the physical distance individuals maintain from others during social interactions, and into which intrusion by others can cause discomfort. Here, we asked whether the size of IPS is affected by manipulation of one's own body representation. To address this issue, in Experiment 1, IPS was measured through a comfort-distance task, before and after eliciting the illusion of owning an invisible body. To rule out a general, nonspecific change in space perception consequent the illusion, we also assessed peripersonal space, e.g., PPS, the area around the body used to act on nearby objects, through a reaching-distance task. Results showed that the experience of invisibility induces a selective contraction of IPS, without affecting the perceived reaching space around the body. In Experiment 2, a tool-use manipulation produced the opposite dissociation, modifying the boundaries of PPS, but leaving IPS distance unaltered. Collectively, these findings support a close relationship between IPS and the conscious representation of the body external appearance, i.e. the body image, and suggest the existence of two functionally separate representations of the space immediately surrounding the body in humans, which may form the basis of distinct processes engaged for different behavioural contexts.