The illusion of having a tall or short body differently modulates interpersonal and peripersonal space

The brain constructs a functional representation of the space around the body, the so called peripersonal space (PPS), which is a sensorimotor interface used to ensure suitable motor acts. However, this sector of space is also involved in social interactions. Individuals indeed, maintain an interpersonal space (IPS) indicating how close they prefer to stand relative to others. Here, we investigated whether a change in one's own body height representation can differently modulate action and social space. To this aim, we measured IPS and PPS in a similar way through a Reaching-distance and a Comfort-distance task, respectively, before and after participants experienced the illusion of having a tall (Experiment 1), or a short (Experiment 2), body. The illusion of having a tall body significantly reduced the IPS and enlarged PPS. On the other hand, the illusion of having a short body contracted the IPS, leaving the PPS intact. A further experiment (Experiment 3), showed that the illusory ownership for the tall or short body is a necessary condition to update the participants' height representation. Thus, a change in body height representation was effective to reveal a dissociation in the representation of the space around the body, depending on whether this sector of space is used for programming actions, or for regulating social interactions.