The brain relies on a constant mix of sight, touch, and movement to decide which body parts belong to you.

Your brain is always solving a puzzle to figure out where you end and the world begins. It combines what you see, what you feel, and how you move. Scientists study this using body ownership illusions, like the famous rubber hand experiment. By brushing a fake hand and your hidden real hand at the same time, your brain gets confused. It quickly accepts the fake hand as your own.