Others' actions reduce crossmodal integration in peripersonal space.

Specific mechanisms integrate visual-tactile information close to the body to guide voluntary action [1, 2] and to enable rapid self-defense in peripersonal space [3-5]. In social interactions, others frequently act in one's peripersonal space, thereby changing the relevance of near-body events for one's own actions. Such changes of stimulus relevance may thus affect visual-tactile integration. Here we show that crossmodal processing in peripersonal space is reduced for perceptual events that another person acts upon. Participants performed a visual-tactile interference task [6] in which spatially incongruent visual distractors in the peripersonal space are known to interfere with judging the location of a tactile stimulus [7-10]. Participants performed the task both alone and with a partner who responded to the visual distractors. Performing the task together reduced the crossmodal interference effect on tactile judgments, but only if the partner occupied the participant's peripersonal space (experiment 1) and if she responded to all, rather than only a subset, of the visual distractors (experiment 2). These results show that others' actions can modulate multisensory integration in peripersonal space in a top-down fashion. Such modulations may serve to guide voluntary action and to allow others' actions in a space of self-defense.