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Abstract:
Ambiguous figure reversal involves a neural mechanism that limits the number of perceptual
organizations that can be consciously experienced at a given moment. So how can perceptual
experience be stable and continuous in the presence of alternative interpretations of the same
physical stimulus? Recent demonstrations using bistable stimuli such as the Necker cube have
revealed that repetitive intermittent presentation leads to a stabilization of the percept [1,2].
According to Gepshtein and Kubovy [3] two temporal processes play an important role in the
perception of ambiguous figures: adaptation and hysteresis. In the present study we investigated
the effects of reference stimulus duration and interstimulus interval length upon transition
probability using ambiguous and unambiguous versions of the Mach Card. On the basis of previous
research findings we predicted that long preexposure periods to the reference stimulus
lead to adaptation effects. Furthermore we hypothesized that the length of the interstimulus interval
between reference and test stimulus affects the subsequent perception of the ambiguous
test stimulus. As expected, participants displayed a convex bias in their responses to the ambiguous
Mach Card reference stimulus—indicating that they perceived the ambiguous Mach
Card as a standing book with the spine pointing towards them. The results of the present experiment
suggest that prolonged duration times of ambiguous and unambiguous reference stimuli
lead to adaptation effects in the perception of the ambiguous test stimulus. Examining the effects
of different interstimulus interval lengths, we demonstrated that short reference stimulus
duration times in combination with long interstimulus intervals seem to lock the percept in
its present state and the subsequent ambiguous test stimulus will be perceived in the identical
configuration. Further analysis will reveal if different adaptation and priming mechanisms are
active for convex and concave images, given the inherent tuning of the visual system to convexity.
The investigation of these history effects will help us to identify the relative contribution of
stimulus-driven and cognitive factors to the perception of ambiguous 3D shapes.
