Why you can't tickle yourself: what your brain knows that your skin does not

Scientists have tickled people with a helper hidden under a table, a machine from 1971 and a robot arm, all to answer one question: why do your own fingers never tickle you? The answer is a trick your brain plays every time you move. You meet the copy it keeps of every order to move, the forecast made by your cerebellum, and sensory attenuation, the turning down of your own touch. The same trick even explains why a push back always comes out harder.