Your space or mine: Trait anxiety affects the peripersonal space plasticity in a social context

Peripersonal space (PPS) is a plastic sector of space surrounding the body whose boundaries are mapped through multisensory integration and shifted by individual motor experiences. To date, nothing is known about PPS plasticity after a social motor interaction, and whether individual traits, such as anxiety, modulate it. Here, participants were instructed to manipulate small objects within their reaching space without tool-use, collaboratively helped by a confederate who employed a tool in her extrapersonal space. Social cooperative motor training shifts PPS's boundaries even if participants’ motor actions are confined within their reaching space. Crucially, trait anxiety steers the shift direction: engaging in a cooperative motor interaction with another unfamiliar person expands PPS in low anxiety people, whereas individuals with high anxiety show PPS shrinkage. Our results show that PPS, built from multisensory signals, plastically adapts to social cooperative interactions, to dynamically define self-other body boundaries.