At first this might sound like a bad practical joke. Begin by tuning a radio to a station playing static. Then lie down on a couch and tape a pair of halved ping pong ballsover your eyes. Within minutes you should begin to experience a bizzare set of sensory distortions.Some people see horses prancing in the clouds or hear the voice of a dead relative. It turns out that the mind is addicted to sensation so that when there’s little to sense (that’s the purpose of ping pong balls and static) your brain ends up inventing its own.