In 1998, two scientists at the University of Pittsburgh, Pennsylvania, did something that sounds almost impossible. They successfully convinced people that a dummy rubber hand was part of their own body.
This is how it worked.
The scientists asked each participant to sit on a chair by the table. They would ask the participant to place one of their hands on the table while the other hand was hidden out of sight, either under the table or behind a screen. Then they would place the rubber hand in front of the participant, where their hidden hand would normally have been.
Next, they would stroke both their hidden hand and the rubber hand simultaneously with a paintbrush. Strangely, within moments the participants started experiencing the touch on the rubber hand. When asked where they were feeling the sensation, they pointed towards the rubber hand.
The key condition for the illusion to work was that the paintbrush strokes had to be in sync. If the strokes were out of sync, the illusion vanished.
After the initial success, the same experiment was replicated many times with slight variations. In some tests, researchers even hit the rubber hand with a hammer and participants would react in shock and distress, despite no real injury.
The experiment demonstrate an interesting thing that our brains can be tricked into believing that an object is part of us, if the conditions are appropriate.