DO YOU EVER want to change the way you see the world? Wouldn't it be fun to hallucinate on your lunch break? Although we typically associate such phenomena with powerful drugs like LSD or mescaline, it's easy to fling open the doors of perception without them: All it takes is a basic understanding of how the mind works.

At first this sounds like a bad practical joke. Begin by turning the radio to a station playing static. Then lie down on the couch and tape a pair of halved ping pong balls over 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 is little to sense - that is the purpose of the ping-pong balls and static - your brain ends up inventing its own.

A. If you happen to have a realistic-looking rubber arm, then this hallucination is for you. Begin by hiding your actual arm behind a box on a table so that you can't see it. Then arrange the fake arm on the table, so that from your point of view it looks like it could be your hidden arm.

B. A friend should then stroke both the real hadn and the rubber hand in the same place and at the same time. After a few minutes, you should feel like the fake limb has become your own flesh.

C. Then have your friend stab the rubber hand, or hit it with a hammer: You will feel a powerful jolt of anxiety and pain, since your brain is convinced that the rubber hand is real.

This requires two chairs and a blindfold. The person wearing the blindfold should sit in the rear chair, staring at the back of the person sitting in front. THe blindfolded person should then reach around and place one hand on the other person's nose. At the same time, he should put his other hand on his own nose, and begin gently stroking both noses. After about a minute, more than 50 percent of subjects report that their nose feels incredibly long.