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Abstract:
A fundamental property of ambiguous visual patterns is the inevitability of perceptual reversal. The rate of alternation generally depends both upon the physical structure of the stimulus as well as the inherent rate of an individual. Here we present evidence that critical to the reversal process is the prolonged physical presence of the inducing stimulus. We demonstrate that when stimuli are shown only intermittently, the rate of perceptual alternation sharply declines to nearly zero in some subjects. In particular, we found that rotating three-dimensional bistable patterns with mean dominance times less than 10 seconds could be stabilized for periods lasting over ten minutes by correctly adjusting the duration of on and off periods. Since either perceptual state could be maintained in this way, this effect did not simply reflect a perceptual bias on the part of the observer. This trend was also present for other bistable patterns, including those involving geometric depth reversals and apparent motion correspondence. We systematically investigated the influence of stimulus on and off durations on the stability of such patterns, and found that minimizing the duration of the stimulus on time was the predominant factor in perceptual stabilization. We suggest that upon removal of the inducing stimulus a visual memory process retains and holds the last perceptual state, which persists and governs the perceptual interpretation during the subsequent presentation. Electrophysiological studies are currently underway to better elucidate the neural mechanisms contributing to this phenomenon.
