Abstract
AimThe present study utilizes perceptual hysteresis effects to compare the ambiguity of Mona Lisa’s emotional face expression (high-level ambiguity) and of geometric cube stimuli (low-level ambiguity).MethodsIn two experiments we presented series of nine Mona Lisa variants and nine cube variants. Stimulus ambiguity was manipulated by changing Mona Lisa’s mouth curvature (Exp. 1) and the cubes’ back-layer luminance (Exp. 2). Each experiment consisted of three conditions, two with opposite stimulus presentation sequences with increasing and decreasing degrees of ambiguity, respectively, and a third condition with a random presentation sequence. Participants indicated happy or sad face percepts (Exp. 1) and alternative 3D cube percepts (Exp. 2) by key presses. We studied the influences of a priori perceptual biases (long-term memory) and presentation order (short-term memory) on perception.ResultsPerception followed sigmoidal functions of the stimulus ambiguity morphing parameters. The morphing parameter for the functions’ inflection points depended strongly on stimulus presentation order with similar effect sizes but different signs for the two stimulus types (positive hysteresis / priming for the cubes; negative hysteresis / adaptation for Mona Lisa). In the random conditions, the inflection points were located in the middle between those from the two directional conditions for the Mona Lisa stimuli. For the cube stimuli, they were superimposed on one sigmoidal function for the ordered condition.DiscussionThe hysteresis effects reflect the influence of short-term memory during the perceptual disambiguation of ambiguous sensory information. The effects for the two stimulus types are of similar size, explaining up to 34% of the perceptual variance introduced by the paradigm. We explain the qualitative difference between positive and negative hysteresis with adaptation for Mona Lisa and with priming for the cubes. In addition, the hysteresis paradigm allows a quantitative determination of the impact of adaptation and priming during the resolution of perceptual ambiguities. The asymmetric shifts of inflection points in the case of the cube stimuli is likely due to an a priori perceptual bias, reflecting an influence of long-term memory. Whether corresponding influences also exist for the Mona Lisa variants is so far unclear.
Highlights
Perceptual ambiguitiesOur senses have only limited access to the environmental information and the available sensory evidence can be to varying degrees ambiguous (e.g., [1])
They were superimposed on one sigmoidal function for the ordered condition
We introduce factors FSTM and FLTM indicating how much the stimulus parameter has to be changed in order to compensate for the memory influence
Summary
Perceptual ambiguitiesOur senses have only limited access to the environmental information and the available sensory evidence can be to varying degrees ambiguous (e.g., [1]). Like Rubin’s vase/face figure [5], Boring’s old/young woman [11], the Necker cube (ambiguity in depth perception [6]) and binocular rivalry stimuli (e.g., [12]) have been used to study ambiguity at lower processing levels (e.g., [13,14,15,16,17]) They have been in the focus of scientists from disciplines like philosophy, cognitive and neuroscience and even physics [15,16,17,18,19] for decades
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