1 In the Leaning Tower Illusion, discovered by Frederick Kingdom, Ali Yoonessi, and Elena Gheorghiu of McGill University, two identical side-by-side images of the same tilted and receding object appear to be leaning at two different angles...
2 The Leaning Tower Illusion elucidates the way in which the visual system uses perspective to help reconstruct 3-D objects. We say "reconstruct" because the visual system has no direct access to three-dimensional information about the world... Photo courtesy Thomas Haltner
3 Further analysis of similar images reveals subtleties in the way our visual system processes the perception of depth and perspective. For instance, the Leaning Tower Illusion also works with paired images of train tracks, violating the rules of perspective... Courtesy of B. Micklethwait
4 However, the illusion does not occur when viewing two leaning Japanese manga girls, even though the two cartoon images are tilted. The reason is that the cartoon girls do not appear to recede in depth, so our brain does not expect that they would converge into the distance... Courtesy of A. Kitaoka
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5 The leaning tower illusion is such a fundamental feature of our visual system that it works even if one draws a 3-D solid object as it recedes into the distance. The parallel lines give the illusion of diverging in the distance... Courtesy of Frederick Kingdom
