Another nice collection of optical illusions.
»Optical illusion« sounds pejorative, as if exposing a malfunction of the visual system. Rather, I view these phenomena as bringing out particular good adaptations of our visual system to standard viewing situations. These adaptations are »hard-wired« into our brains, and thus under some artificial manipulations can cause inappropriate interpretations of the visual scene. As Purkinje put it: »Illusions of the senses tell us the truth about perception« (cited by Teuber, 1960).