This week's introductory psychology class introduced students to a magician's take on optical illusions. His name is Jerry Andrus and a little googling found that he makes appearances every so often in Corvalis, OR. Besides introducing young people to the wonders of the Monte Hall problem and a rotating spiral illusion, he constructed an impossible box that I think is very neat.
It's very similar to the Penrose triangle illusion. A larger than life one can be seen in Australia (see the photo to the right). There's also one located on the campus of Willamette University in Salem, OR. No Photoshopping tricks are involved. Just arrange the elements the right way and take the photo from the perfect vantage point. If you've got the time, it is possible to create a desk sized impossible triangle out of cardboard.
The Ames room is another neat optical illusion that plays on the way our sensory system processes depth. The two girls are identical twins yet one appears much larger. The diagram below shows how the room is constructed. If you have time, a desk sized one could be made. Two pennies could take the place of the girls.
What's really weird is that a couple of psychologists found that when women view their spouse inside an Ames room, they perceive less size distortion than when viewing a stranger! This effect didn't occur for men viewing their wives though, and the degree of distortion perceived was inversely related to how much love and trust each woman felt for her husband.
This shadow illusion is fun. When looking at the shaded squares it is difficult to believe they are actually the same color as the "darker" unshaded squares in the checkerboard.
Can you believe these two tables are exactly the same size?