Schrauf, M., Lingelbach, B., Wist, E.R. (1997) The scintillating grid illusion.  Vision Research ,  37,  1033-1038. 

Schrauf, M., Lingelbach, B., Wist, E.R. (1997) The scintillating grid illusion. Vision Research37, 1033-1038. 

Michael Bach is a professor of Ophthalmology at the University of Freiburg. His award winning site, 84 Optical Illusions and Visual Phenomena seems to be the best single introduction to visual illusions on the web. It receives an enormous amount of daily traffic. Most of the demonstrations are interactive animations.


This unit of inquiry requires internet access, preferably with laptops. Students work in pairs. They spend a full 20 minutes exploring Michael Bach's site in some depth. To discourage superficial surfing, students are told that several pairs will chosen at random to champion their favorite illusion. They will present to the entire class their chosen illusion and add their own insights.

To warm up the class, students could see Ramachandran's discombobulating video on the Ames room and the collection of solid illusions presented by Jerry Andress. These Youtube videos last only a few minutes but may stimulate enthusiastic discussion.