The reason for this conundrum is that the command to tickle yourself is going through the same brain that usually responds to the sensation with a wriggly giggle, and the one cancels out the other.
Or as Sara-Jayne Blakemore, a researcher at the Institute of Cognitive Neuroscience at University College London, explained it to Scientific American in 2007:
“The cerebellum can predict sensations when your own movement causes them but not when someone else does. When you try to tickle yourself, the cerebellum predicts the sensation and this prediction is used to cancel the response of other brain areas to the tickle.”
However, schizophrenics are able to tickle themselves. Researchers say it could be because they can’t link the tickle to their initial motive.read more