About 10 years ago, psychologists in Pennsylvania discovered an amazing illusion. They found that they could convince people that a rubber hand was their own by putting it on a table in front of them while stroking it in the same way as their real hand.
The now-famous "rubber hand illusion" was not only a mind-blowing party trick, it was also hugely important in understanding how sight, touch and "proprioception" - the sense of body position - combine to create a convincing feeling of body ownership, one of the foundations of self-consciousness.
In recent years that understanding has been explored further using increasingly freaky illusions. "The rubber hand illusion really inspired people," says Henrik Ehrsson, a neuroscientist at the Karolinska Institute in Stockholm, Sweden.
He is one of many researchers who have taken the illusion and run with it, creating a whole new set of "bodily illusions" that mess with our sense of self in strange and disturbing ways. "We're doing all kinds of crazy stuff," he says.