Auditory and visual stimuli alter tactile motion perception

Recently Sekuler et al. [1] investigated the motion-bounce illusion and found that sound can influence ambiguous visual motion perception. Here we investigated the motionbounce illusion in the tactile-auditory and the tactile-visual domain. Using a vibro-tactile belt consisting of 7 vibrators we generated tactile apparent motion stimuli by sequentially activating neighboring motors with an onset of 200ms between the motors. Starting at the left and the right hip, two tactile motion stimuli run towards each other. On the body midline an ambiguous event was perceived: either the transition of both stimuli with continuing motion trajectories or a bounce event followed by the reversal of the movement direction. Presenting just the tactile motion stimulus resulted in an ambiguous percept. In the tactile-auditory condition the presentation of an auditory beep 200ms before the collision was sufficient to disambiguate the percept such that a significantly higher proportion of bounces was reported. The presentation of the sound at the time of the tactile collision event or 400ms before reduced the proportion bounces reported and became indistinguishable from the uni-modal baseline condition. In the tactile-visual condition the presentation of a light flash at the time of the tactile collision, 200ms or 400ms before the collision induced a higher proportion of bounce reports. This indicates that the temporal window of audio-tactile integration is comparable to that found in the visual-auditory domain. These results suggest that similar supramodal mechanisms exist for apparent motion perception.