08-06-2026, 06:28 PM
![[Image: Bulge02.jpg]](https://www.psy.ritsumei.ac.jp/akitaoka/Bulge02.jpg)
Summary
Akiyoshi Kitaoka's page presents his checkered illusion, a geometric optical illusion built entirely from squares that nonetheless appears to bulge outward, curve, or tilt — as seen in the flagship "A bulge" image, a version where a perfectly horizontal row of squares looks tilted counterclockwise, and variants (including one by researcher Jacques Ninio) that reproduce the effect using circles instead.
Kitaoka attributes the distortion to a contrast-polarity model, linking it to the well-known Café Wall illusion, and cites three of his peer-reviewed papers (1998, 2004, 2007) as the underlying research. Note: this source is a visual gallery with image captions and citations, not a prose article with an argument — so this is more a description of its content than a true summary.
ARTICLE
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