Abstract
The visual system continuously resolves ambiguity within the retinal information with respect to the shape as well as relative size and speed of objects by applying heuristics such as the Gestalt principles. With more than one object moving in a dynamic scene, the correspondence between object locations over time also needs to be disambiguated. Here, we study this phenomenon using displays in which two discs move toward each other, superimpose in the center of the screen, and then moved apart. This display is perceptually ambiguous because it is consistent with the interpretation of two discs streaming past each other as well as the interpretation of two discs bouncing off each other. We show that the visual system incorporates coinciding tactile information in order to disambiguate the motion paths of two dynamic objects by measuring explicit impressions (i.e., asking participants whether they perceive streaming or bouncing) as well as implicit perceptual processes (i.e. the perceived overlap between the moving discs). In the first of two experiments, we observed that the dominant interpretation of the motion paths switched from streaming to bouncing when a brief vibrotactile stimulation (applied to the left hand of the participants) coincided with the moment of overlap between the two moving discs. In the second experiment, the participants adjusted the overlap between two additional static discs until it matched with the perceived overlap of the ongoing bouncing/streaming event. The results of this experiment showed that coinciding tactile stimulation also reduced the perceived overlap between the two moving discs thus leaving a larger uncovered illusory crescent. In return, this larger crescent might induce the impression of bouncing rather than streaming. Our results therefore suggest that the tactile information indeed altered the visual percept of the dynamic event rather than the subsequent cognitive interpretation of an otherwise unaffected visual percept.
Meeting abstract presented at VSS 2017