Richard Wiseman is Professor of the Public Understanding of Psychology at the University of Hertfordshire in the United Kingdom. He's also one of my heroes. Wiseman has made a career out of bringing the academic study of Psychology to the people, and he does it with a brilliant sense of humor and wonder. Check out the illusion he illustrates in this video. It's only a minute long and it will blow you away, it did me at any rate.
I talk a lot in my design practice about fooling the eye and making things disappear. I'm usually talking pretty figuratively but Professor Wiseman's being literal here. His video proves the point brilliantly that human brains, fantastic machines though they be, can be fooled. Remember that the next time someone sees Jesus in a Frito. Remember it too when someone like me tells you that he can make a flaw in a room disappear. If you know the rules, anything's possible.