Orientation Misperceptions Induced by Contrast Polarity: Comment on “Contrast Polarities Determine the Direction of Café Wall Tilts” by Akiyoshi Kitaoka, Baingio Pinna, and Gavin Brelstaff (2004)

According to Kitaoka et al (2004, Perception 33 11–20), the Café Wall illusion can be reduced to misalignment effects produced locally by a large shape on a line passing nearby. I demonstrate here that the interacting units are edges and not whole shapes, and that the source of the illusion does not consist in a local tilt but in a tendency of the edges to join when they have the same contrast polarity.