Long-term persistent state in vision M Wexler, M Duyck, P Mamassian |
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Laboratoire Psychologie de la Perception, CNRS & Université Paris Descartes, France
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| Low- to mid-level vision is usually thought of as a stateless input-output process, or as involving state that persists over seconds or at most minutes, as in adaptation or multistability phenomena. Here we document two visual state parameters with much longer state dynamics. We study two stimuli, both involving depth perception from motion, whose perception is affected by strong biases in nearly every observer. These biases are continuous, angular variables that can be inferred robustly from binary perceptual reports on multiple bistable stimuli. In an experiment on about 700 subjects, we have measured population distributions of these two biases. Both distributions have local peaks in the cardinal directions and are significantly non-uniform, but are otherwise different and uncorrelated. About 250 subjects repeated the experiment two weeks later, and most had nearly unchanged biases; the median change was only 8 and 11 deg in the two parameters. In spite of this apparent stability, we also show that these biases can fluctuate spontaneously, after viewing many hundreds of stimuli but also after periods in darkness. |
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