Item

Abstract

Recently Sekuler et al. [1] investigated the motion-bounce illusion and found that sound can
influence ambiguous visual motion perception. Here we investigated the motion-bounce illusion
in the tactile-auditory and the tactile-visual domain, respectively. 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 flashlight 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.