Why can’t I tickle myself?

Because if you tickle yourself, you know what to expect. When someone else tickles you they can send you into spasms by touching you in unpredictable ways. This has been demonstrated using a robotic tickling arm. People could not make themselves laugh as long as the arm moved in real time, but if a delay was introduced so they couldn’t predict the effect of their movements they found the effects ticklish again. Although tickling can be fun, it can also be unpleasant or even painful. The laughter it causes is involuntary and not necessarily a sign of pleasure.
Answered by Susan Blackmore