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Mark Wexler, Pascal Mamassian; Biases in multistable displays as dynamic state variables. Journal of Vision 2014;14(10):399. doi: 10.1167/14.10.399.
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© ARVO (1962-2015); The Authors (2016-present)
Observers show idiosyncratic biases in the perception of multistable stimuli, such as in the perception of tilt from structure-from-motion stimuli and in the perception of depth order in motion transparency. By measuring biases across a sampling of all surface tilts and motion directions, we show the perception of these stimuli in a vast majority of observers is governed by internal state variables, one for preferred tilt and one for preferred motion direction. These state variables are directions in the image plane. The predominant pattern is that only tilts within 90 deg of the preferred tilt are perceived; in the motion domain, motions with direction within 90 deg of the preferred motion direction are perceived closer to the observer in transparency displays (see Mamassian & Wallace, JOV 2010, for older results on the transparency display). We measured population distributions of these state variables in nearly a thousand subjects, and have found anisotropic distributions with peaks in the cardinal directions and suprising asymmetries, as well as lack of any correlation between the shape and motion variables. The state variables can be perturbed using carefully chosen unambiguous stimuli, showing attraction to the unambiguous direction, but then systematically relax to their initial values over tens of seconds. Change in the variables does occur naturally, and seems to be driven by internal dynamics rather than external stimulation. Over a two-week period, the median change in the state variables is about 10-15 deg; over one year, it's about 20-30 deg. When measured every day over extended periods, the dynamic behavior of the state variables shows a wide variety of behaviors: periods of stability, sudden transitions, rapid there-and-back excursions, oscillations between discrete values, and slow drifts. These unsuspectedly rich patterns of behavior open a window onto the internal functioning of the visual system.
Meeting abstract presented at VSS 2014
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