Science Puzzle
Why Can’t You Tickle Yourself?
Try to tickle yourself and nothing happens. The same wiggling fingers on your ribs from a friend would have you helpless with laughter.
Why can't you tickle yourself?
The Answer
Because your brain saw it coming. Every time your brain sends a command to move your hand, it also keeps a copy of that command and uses it to predict exactly what you are about to feel. When the touch arrives precisely as predicted, the brain dampens the sensation. It has decided this is old news, not worth a reaction.
Tickling depends on surprise, on your nervous system being caught off guard. Your own fingers can never surprise you, because your brain scripted their every move a fraction of a second in advance. Someone else's fingers are unpredictable, so the touch arrives unfiltered and at full strength, and you squirm.
This prediction system does far more than spoil self-tickling. It is how you can hold a cup without crushing it and walk without watching your feet, because your brain is constantly forecasting the results of your own actions.
The principle: Predictive processing in the nervous system. The brain forecasts the sensory results of its own commands and suppresses them, so only unpredicted sensations feel strong.