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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 systematically investigated the influence of stimulus on and off durations on the stability
of such patterns, finding that minimizing the duration of the stimulus “on time” was
the predominant factor in perceptual stabilization.
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 time 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 suggest that upon removal of the inducing stimulus a visual memory process retains
and hold 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.
