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Seiichiro Naito, Yoshihiro Hirano, Satoshi Kikuchi; Loss of position perception and size constancy for equiluminant counterphase flickering color stimuli. Journal of Vision 2006;6(6):230. doi: https://doi.org/10.1167/6.6.230.
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© ARVO (1962-2015); The Authors (2016-present)
The subjects observed two overlapping concentric equiluminant red and green circles. Their colors alternate at 10 Hz. The circles subtended at 15 and 7 degree visual angles on a black background. Over the inner circle, a white fixation point moves slowly back and forth. Subjects would perceive the displacing motion of the stationary inner circle. It migrates back and forth sometimes following the fixation point, and at other times evading the point. The apparent motion is generally unstable and inconsistent. Nevertheless, the magnitude of the illusion could be measured. Subjects could produce an equivalent motion impression on a neighboring screen with similar non-flickering circles. The typical apparent displacement distance is approximately 10% of the inner circle radius. The luminance range over which subjects observed the illusory motion suggests that it has mangnocellular properties. While the moving fixation point helps the illusion, it is not essential to the condition. Subjects could observe indefinite motions with slow voluntary eye movements over the inner circle. The geometry of the stimuli does not necessarily have to be a circle. Two rectangles produce similar results. Additionally, the subjects observed that the size constancy is not applicable for the inner circle. They changed the observing distance back and forth by approximately a foot in a few seconds. Significant size changes of the inner circle could be observed. When he/she was going away from the screen, the inner circle would extend its size, and vice versa.
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