This predictability that you develop between your own actions and the resulting sensations is the reason you cannot tickle yourself. Other people can tickle you because their tickling maneuvers are not predictable to you. And if you’d really like to, there are ways to take predictability away from your own actions so that you can tickle yourself. Imagine controlling the position of a feather with a time-delay joystick: when you move the stick, at least one second passes before the feather moves accordingly. This takes away the predictability and grants you the ability to self-tickle.
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