First, Arvid Guterstam made himself invisible. When he looked down at his body, there was nothing there.
He could feel he was solid; he hadn’t vanished into thin air. He even felt a paint brush tickle his transparent belly, while the brush appeared to be stroking nothing but air.
Being invisible is “great fun,” Guterstam reports, “but it’s an eerie sensation. It’s hard to describe.”
Then he took off his virtual reality headset and was back in the laboratory, fully visible. Guterstam is a medical doctor and PhD student, and he had just pulled off the first fully convincing illusion of complete invisibility. He went on to test 125 other people, and reports Thursday in Scientific Reports that seven out of ten also felt the illusion, and it was realistic enough to make them feel and respond physically as if a group of people could not see them.
One day, just maybe, cloaking devices might make human invisibility possible. Guterstam wants to know what that will feel like—and what these people might do. How about their morals? If you take away the chance of being caught, will people, as we might suspect, lose their sense of right and wrong?
But before he can test the moral fortitude of the newly transparent, Guterstam has to get people to feel completely invisible. He and his colleagues in Henrik Ehrsson’s laboratory at Sweden’s Karolinska Institute have succeeded at many other body-morphing illusions, including making my Phenomena colleague Ed Yong feel in turn that he had left his body, shrunk to the size of a doll, and grown a third arm.
They already convinced people they had an invisible hand. But what about the whole body? “This is definitely pushing the boundaries of how bizarre an illusion of this kind can get,” Guterstam says.
This time, they had people put on a virtual-reality headset that showed the view from a second headset, mounted at head height on nothingness. If you were in this getup, a scientist would touch you with a paint brush while simultaneously touching the nothingness in the same place, as though a body were there. So as you felt the brush, your eyes would be telling you that the brush was touching your nothingness body.
When a scientist swiped a knife toward the invisible belly, people’s heart rates went up and they broke out in a sweat, the classic stress response. When put in front of an audience of serious-looking people staring them down, “visible” people also got stressed. But the “invisible” people—not so much. They felt so completely invisible that their bodies responded as though they really were invisible. Since the audience couldn’t see them, there was no reason to feel uncomfortable.
The illusion works because, as the team has learned from these tricks, it’s shockingly easy to create an out-of-body experience. Our sense that we reside within our bodies—what we can think of as our sense of self—is not fixed. Instead of being firmly locked in our body, our sense of self can float free, as if on a tether.
Our brains, it appears, create this body sense moment by moment, continuously monitoring our senses and putting the “me” where those senses say it should be. Move the senses, and you move the me. All it takes is creating a mismatch between where I see I’m being touched and where I feel it.
This is all very interesting, but what do we do with it? Well, Ehrsson’s group is also working on better prosthetic devices for amputees, that would harness the sense of self to make the prosthetic feel like a true body part. One day, we might even control robots with our movements and actually feel that we’ve jumped into the robotic body.
And then there’s the dream of actual invisibility, with all its moral dilemmas. For now, we don’t need to fret too much: The closest we’ve gotten is disappearing a cat and a goldfish, and only behind a fixed cloaking device and from the right angles.
All this talk of invisibility leads, inevitably, to The Question. A question whose answer, many believe, says something deep about each of us. If you could be the only person on Earth with a superpower, and you could choose between flight and invisibility, which would you choose?
Flight, many feel, is the noble choice. Invisibility is for thieves and perverts. Yet when we’re honest with ourselves, that’s exactly what many of us are, so invisibility maintains its secret allure.
And Arvid Guterstam? “I would probably say flying,” he says.