80 Optical Illusions & Visual Phenomena 
(Visual Illusion · Optische Täuschung)

These pages demonstrate visual phenomena, and »optical« or »visual illusions«. The latter is more appropriate, because most effects have their basis in the visual pathway, not in the optics of the eye. When I find the time I will expand the explanations, to the degree that these phenomena are really understood; any nice and thoughtful comment welcome.

You may be glad to know: There are no tasteless surprises here; you know, these infantile pranks where you scrutinize a picture and suddenly an ugly face (or the opposite end) screams at you…

Don’t distress yourself if you don’t see the effect described, even if trying carefully. For many illusions, there is a small percentage of people with perfectly normal vision who just don’t see it, for reasons currently unknown.

Most visitors of this site are not vision scientists, so you might find the explanatory attempts too highbrow. That is not on purpose, but, like any science, vision research just is not trivial. So, if the explanation seems gibberish, simply enjoy the phenomenon ;–). Otherwise, there is a short paper: Bach & Poloschek (2006) Optical Illusions primer.

»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« in 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).

Before we delve in, I’d like to express my thanks to the many visitors who gave overwhelmingly positive feedback, adding constructive advice on content, style and typography; please do keep it coming! [Or use the new guestbook.] I have also been able to improve explanations when convincing scientific evidence was sent ;-). Yes, it does take sizable resources to set up and maintain this, but it is also very rewarding, bringing me into contact with so many charming people. Should you want to give back, simply link to this page or use the donation link ;-). Any advice is appreciated – and, yes, for a non-native speaker, English does represent sizable challenges.

Thanks to Inga who created new artwork (4-2005) for the ‘eyes’. More from the Bach Family: Oliver, Christine, Andreas

Low rates from my reliable web service provider Netbeat –in spite of huge traffic– are gratefully acknowledged.