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Abstract

The visual instability that results from viewing ambiguous or conflicting patterns is thought to reflect dynamic processes that are critical for perceptual organization during normal vision. We have recently discovered a method to prolong states of perceptual dominance up to two orders of magnitude by periodically switching off and on the inducing bistable pattern. In the current study we used this paradigm to temporally interleave the presentation of pairs of ambiguous stimuli at the same location in visual space. Bistable patterns including rotating three-dimensional objects, depth reversals, and binocular rivalry, were shown alternately with appropriate blanking periods to prolong phases of perceptual dominance. We were interested under what conditions the time courses of two parallel bistable visual processes would be independent. We found that for certain pairs of ambiguous stimuli, such as 3-D balls rotating around orthogonal axes, the time course of perceptual alternation was largely parallel and independent. However, for other patterns, e.g. those differing only in color, speed, size, or position, the two stimuli were synchronized in their reversals. These results suggest that for a given visual location, perceptual organization can be biased for multiple different stimuli simultaneously, but that the independence between pairs of stimuli depends upon their similarity. We will discuss the results with respect to the critical stimulus dimensions that determine whether or not interference occurs.