Relationship between multisensory integration and the different spaces around the body

Several spaces around the body have been described contributing to the interaction with objects (peripersonal space) or people (interpersonal and personal spaces) and presumably implying multisensory integration. We investigated the relationship between these different spaces by requiring participants to indicate when an approaching stimulus (human, robot or lamp) was reachable (peripersonal), at the most comfortable distance to interact with (interpersonal) or causes discomfort (personal). Results showed that participants preferred to place all stimuli further away than peripersonal space, but felt uncomfortable when the stimuli were well inside peripersonal space. In addition, all three spaces were positively correlated, supporting the view that peripersonal action space contributes to the regulation of social distances. We also investigated trunk-centred visuotactile multisensory integration. We found that multisensory integration extended beyond all spaces and correlated to personal space, suggesting it is involved in interactions both with objects and people but fundamentally associated with a defensive purpose.