Abstract
Apparent motion is an illusion in which static objects are perceived to be in motion when presented in quick succession. We investigated the interplay between cross-modal interactions of visual and tactile stimuli and attentional control over perceptual selection. We used a novel paradigm that combined apparent motion synchronously presented in both visual and tactile domains. As visual stimuli we used ambiguous motion quartets where the probabilities of horizontal and vertical percepts are equal. The tactile illusion of apparent motion was created using pairs of vibrotactile signals produced by a stimulation array of four solenoid tappers attached to the palmar surface of the upper and lower phalanxes of the middle and index fingers of the left hand. Ten subjects participated in two experiments. In Experiment 1, only visual stimuli were presented continuously in the peripheral visual field (15° from the fixation dot) and participants were instructed either to (a) passively report their percept of the apparent motion, (b) switch the direction of motion as quickly as possible, (c) hold the current motion direction as long as possible. The phase durations of the hold and switch conditions were significantly longer and shorter, respectively, than the phase durations of the passive condition. This demonstrates the ability of participants to select and attentively hold one of the alternating visual percepts. In Experiment 2, the visual stimuli were rhythmically synchronous with apparent tactile motion and the observers still had to report their perception under the three different instructions. The participants could hold the horizontal percept for significantly longer periods when the visual stimuli were presented in combination with synchronous congruent tactile stimuli. The experiments demonstrate that combinations of rhythmically synchronous visual and tactile stimuli enhance healthy observers' attentional control over what they perceive.
Meeting abstract presented at VSS 2016