Cool collection of optical illusions

dolphinsex.jpg

Scientific American is doing a whole issue on optical illusions and they've got a sampling up on their website as a slideshow. It's interesting to see how some illusions are created by physical tricks of the eyes, while others are, apparently, psychological in nature. This illusion, for instance, is supposed to be influenced by the way sexual maturity changes your frame of mind—kids see dolphins and grown-ups see, well, sex.