Cite as:
Ashida H, Kitaoka A, Sakurai K, 2002, "A Fourier approach to the Ouchi-type anomalous-motion illusion" Perception 31 ECVP Abstract Supplement

A Fourier approach to the Ouchi-type anomalous-motion illusion

H Ashida, A Kitaoka, K Sakurai

An illusory sliding motion is perceived in a rectangular checkerboard pattern that is surrounded by an orthogonally oriented pattern (Ouchi illusion: Spillmann et al, 1993 Investigative Ophthalmology & Visual Science 34(4) 1031). This illusion has been explained in the image space by the bias toward the normal motion vector of the longer edge (Fermüller et al, 2000 Vision Research 40 77 - 96; Mather, 2000 Perception 29 721 - 727). We created a variant of the Ouchi figure by replacing the black rectangles with thin lines, which produces a comparable motion illusion. This figure has the advantage that we can mix up the spatial-frequency spectrum by randomly shifting each line element, without a significant disorder of the edge structure. A rating experiment revealed that the illusion is diminished as the line shift becomes larger, that is as the power at the fundamental spatial frequency decreases. The results suggest that the Ouchi illusion will be further understood in Fourier spatial-frequency space. The fundamental components (and possibly several harmonics) are considered crucial. The illusory relative motion must be related to the directional biases for type II plaids (Ferrera and Wilson, 1990 Vision Research 30 272 - 287), which arise in different directions in the inner and the outer areas of the Ouchi figure.

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