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Akiyoshi Kitaoka, Ikuya Murakami; Rotating Ouchi illusion. Journal of Vision 2007;7(9):984. doi: https://doi.org/10.1167/7.9.984.
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© ARVO (1962-2015); The Authors (2016-present)
We devised a new method to observe the Ouchi illusion more easily than the original image made up of elongated checker patterns. The new image consists of ‘spiral’ checker patterns, in which black and white parallelograms are drawn along Bernoulli's spirals. Of the four ‘sides’ defining each parallelogram, the top and bottom are drawn along Bernoulli's spirals of a particular orientation while the other two are Bernoulli's spirals of a different orientation. When observers approach or move away from the image while fixating at the center, the image appears to rotate clockwise or counterclockwise depending on the orientations of the spirals assigned to the shorter sides and the longer sides. We examined apparent rotation by systematically changing the orientations of spirals. As a result, for most of the images examined, observers reported apparent rotation in the direction that agrees with the prediction from the aperture problem. That is, for the physically expanding/contracting retinal image, the perceived motion of each edge was biased toward the perpendicular direction to the local edge orientation, thus creating rotary global motion. However, the opposite direction was also reported in some cases. We argue that these results are reconciled in terms of Fourier components in the image.
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