This is crazy. Just thinking, or believing, can bring about an actual feeling.
via Science Girl
Sight, touch and proprioception (a sense of body position) all combine to convince this person that a rubber hand is their body part. Proprioception refers to the body’s ability to perceive its own position, closing your eyes and touching your nose is one example.
Here’s one from National Geographic:
I love this idea. Gary used to teach it in Bio-anatomy.