2005 volume 34(4) pages 381 – 390
doi:10.1068/p5060

Cite as:
Ashida H, Kitaoka A, Sakurai K, 2005, "A new variant of the Ouchi illusion reveals Fourier-component-based processing" Perception 34(4) 381 – 390
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A new variant of the Ouchi illusion reveals Fourier-component-based processing

Hiroshi Ashida, Akiyoshi Kitaoka, Kenzo Sakurai

Received 17 March 2003, in revised form 15 April 2004; published online 13 April 2005

Abstract. We report that anomalous motion illusion in a new variant of the Ouchi figure is well predicted by the strength of its Fourier fundamentals and harmonics. The original Ouchi figure consists of a rectangular checkerboard pattern surrounded by an orthogonal rectangular checkerboard pattern, in which illusory relative motion between the two regions is perceived. Although this illusion has been explained in terms of biases in integrating one-dimensional motion signals to determine the two-dimensional motion direction, the physiological mechanism has not been clarified. With our new stimuli, which consisted of thin lines instead of rectangles, we found that the perceived illusion is drastically reduced when the position of each line element is randomly shifted. This is not predicted by simple models of local motion integration along the visible edges. We demonstrate that the relative amplitude of the relevant Fourier fundamentals and harmonics leads to a quantitative prediction. Our analysis was successfully applied to other variants of the Ouchi figure (Khang and Essock 1997 Perception 26 585 - 597), closely predicting the reported rating. The results indicate that the underlying physiological mechanism is sensitive to the Fourier components of the stimuli rather than the visible edges.

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