Drifting triangles illusion and its enhancement by shaking or blinking

K Yanaka1, T Hilano2, A Kitaoka3

1Faculty of Information Technology, Kanagawa Institute of Technology, Japan
2Kanagawa Institue of Technology, Japan
3Department of Psychology, Ritsumeikan university, Japan

Contact: yanaka@ic.kanagawa-it.ac.jp

We found a new optical illusion in which many longwise isosceles rectangles of the same shape are arranged so that their bases become mutually parallel and they appear to move in the direction of the bases of triangles contained inside them. The triangles look like a shoal of fishes swimming slowly. Various still images can be perceived as moving. Among them, CDIs and PDIs, including the Fraser-Wilcox illusion and Kitaoka’s optimized Fraser-Wilcox illusion, have a feature where the direction of motion is decided only by the illusory image. Most such illusory images require at least three gray levels, for example, black, gray, and white. The known exceptions are very rare and are only the drifting arrows and convex-directed motion illusions, both of which were found by Kitaoka [http://www.psy.ritsumei.ac.jp/~akitaoka/CRESTmeeting2012.html]. This new illusion also requires only two gray levels of black and white. In addition, it is quite simple because it consists of black rectangles on a white background and vice versa. Furthermore, the effect of the optical illusion is strengthened when the image is shaken in the direction perpendicular to the direction of illusory motion or by blinking between the original and reversed images at a frequency of several Hz.

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