Sensations predicted from one's own movements are registered as weaker than identical sensations produced by someone else.
The canonical demonstration is self-tickling, which fails: a self-generated touch is predicted by the motor system and its sensory consequence is discounted before it reaches awareness. The mechanism keeps the world stable by subtracting what the body itself caused, which is also why a small delay or displacement between action and sensation restores the full sensation.
In practice
- A keyboard with a perceptible lag feels wrong in a way an equally slow colleague's typing does not.
- A passenger feels every movement of a car the driver does not notice making.