Seeing the body modulates audiotactile integration

Audiotactile integration has been studied using various experimental setups but so far crossmodal congruency effects (CCEs) have not been found for tactile targets paired with auditory distractors. In the present study we investigated whether audiotactile CCEs exist and, if so, whether these CCEs have similar characteristics to those found by previous authors with visual distractors. We measured audiotactile CCEs by attaching four vibrators to the backs of participants and presented auditory stimuli from four loudspeakers placed, in separate blocks, at different distances in front of or behind the participant's body. Participants discriminated the elevation of tactile stimuli while ignoring the auditory distractors. CCEs were found only when participants were provided with noninformative vision of their own body, as seen from behind via a camera and head-mounted display; they were absent when participants did not view their body. Furthermore, in contrast to visuotactile CCEs, audiotactile CCEs did not depend on whether the distractors were presented on the same or different side as the tactile targets. The present study provides the first demonstration of an audiotactile CCE: incongruent auditory distractors impaired performance on a tactile elevation discrimination task relative to performance with congruent distractors. We show that audiotactile CCEs differ from visuotactile CCEs as they do not appear to be as sensitive to the spatial relations between the distractors and the tactile stimuli. We also show that these CCEs are modulated by vision of the body.