How do humans know where the self ends and the world begins?

It’s a feeling that’s central to everyday experience and vital for survival, but it can easily be disturbed. Take the classic rubber-hand illusion. A person’s real hand is hidden from view while a rubber hand is placed in full view. When both hands get tapped at the same time, the person may begin to feel that the rubber hand is their own. But even slight variations in timing can make this uncanny feeling fade.

So how does the brain keep track of when different sensory signals come in from the body?