The Beeblebrox Illusion: scientists convince people they have three arms

Zaphod Beeblebrox is just one ofseveralcharactersfrom science-fiction and mythology to have extra arms. It’s a common enough trope, but would it actually work in real life? Could the human mind, which is so accustomed to controlling two arms, cope with a third or fourth one? According to Arvid Guterstam from the Karolinska Institute, the answer is yes. By placing a rubber right hand next to a person’s real one, and stroking both at the same time, Guterstam managed to convince people that they had a third arm. Guterstam works in the lab of Henrik Ehrsson, who has spent many years studying how we come to feel that we own our body. It’s such a natural aspect of our lives that it seems bizarre to question it. But Ehrsson’s work shows how easy it is to mess with this sense of bodily ownership. With a combination of cameras, virtual reality headsets ...