4. BECOME A LIVING DOLL
Remember old sci-fi movies like Attack of the 50-Foot Woman or the more recent Honey, I Shrunk the Kids? Ehrsson’s team at the Karolinska Institute has reproduced a semblance of their plots by giving test subjects the sensation of swapping bodies with an 11½-inch Barbie doll or a 13-foot-tall mannequin.
As in prior self-perception experiments, participants wore head-mounted displays connected to two video cameras. This time the subjects were positioned in beds on their backs while two cameras sent them images of a tiny doll or an oversize mannequin lying on a bed next to them. The cameras assumed the same perspective as the person, looking down at the doppelgänger. When test participants gazed through their video-connected goggles toward their feet, therefore, their bodies appeared to be the size and shape of the artificial one nearby. A researcher stroked the fake body with a rod while softly touching the real body of the volunteer in exactly the same way. Participants quickly got the bizarre feeling that they were inhabiting the body of the small doll or huge mannequin.
Not content to rely on the participants’ subjective descriptions of their reactions, Ehrsson came up with objective evidence documenting the intensity of the body-projection experience. He measured the volunteers’ evoked skin-conductance response—a change in sweating, and hence electrical conductance, due to stress—while they observed someone threatening or cutting the doll with a knife. Skin conductance rose in step with the apparent level of threat, just as it does when a person faces a genuine possibility of physical harm.
During the time the volunteers felt they were inside the artificial bodies, Ehrsson and his team also asked them to look at blocks across the room and estimate how far away and how large those objects were. Then the subjects were asked to walk over to the blocks with their eyes shut. People who had projected themselves into a small body tended to overestimate how far away and how large the blocks were. For those who experienced themselves in the large fake body, the opposite was true: They thought the blocks were much smaller and closer than they actually were.
Ehrsson suggests that such out-of-body illusions could have practical uses. They might one day allow a surgeon to feel as if he or she were inhabiting a microscopic medical robot, directing operations inside a human patient. Or a worker might project himself into a giant robot, maneuvering it as if it were his own body to make repairs at a nuclear power plant.
DIY: How to get small (or large)
Want to project your body into a race car or a potted plant? Forget it. Your best bet is a humanoid form. Your target object probably needs a trunk, two arms, two legs, and a headlike thing. Even a monkey might work. But if you want to inhabit your cat or dog, the territory is uncharted; scientists have not yet attempted a human-to-animal shift in the lab. Experiments have shown that you cannot swap places with a geometric shape, even if it is stroked in synchrony with your body.
5. THE TOTAL BODY SWAP
In recent experiments, Ehrsson has tried what he describes as the most extreme example of swapping bodies yet: producing out-of-body experiences in volunteers who face their own bodies and shake their own hands, seeming to encounter themselves from the outside.
He devised an experiment in which an investigator wears a specially designed helmet equipped with two video cameras that capture images from the investigator’s viewpoint. A research subject wearing a head-mounted display stands opposite the investigator, but instead of seeing what’s in front of him, the subject sees video of the images passing in front of the investigator’s eyes. To the subject, it feels as if he is looking at himself. Then each subject is told to reach out and shake the right hand of the experimenter for two minutes, until the sensation that he is shaking hands with himself becomes overwhelming. The feeling is that of the classic out-of-body experience: You are standing outside yourself, looking in.
DIY: How to teleport yourself
Even if you aren’t a Trekkie, you probably know the phrase “Beam me up, Scotty” from the vintage Star Trek television show. In that ultimate version of high-speed travel, a person’s atoms are disconnected, transported, and reassembled at the destination of choice. A real-life (but alas, only perceptual) version of beaming is currently under development by Mel Slater, a professor of virtual environments at the ICREA research institute at the University of Barcelona. Unlike the Star Trek approach, Slater keeps bodies intact while transforming their sense of location. The participant needs to wear virtual reality gear: a motion-capture suit and goggles connected to a real-time, 3-D video of a location—a conference, to pick a dull but practical example. People at the conference would see an avatar of the participant or a humanoid robot that embodies the person who has body-swapped in. The next step is adding a sense of touch to the simulation, so a person beaming to a remote location could feel himself hugging or shaking hands with a colleague far away.
Slater’s ultimate goal is nothing less than dissolving “the boundary between the human body and surrogate representations.” If he succeeds, paralyzed people could someday be connected wirelessly to humanoid robots and experience the physical world. A few researchers have already tested implants that can read brain waves of paralyzed people. A head-mounted display connected to a video camera, auditory pickup, and other sensors in the robot would let such patients virtually move about and experience the world, even though their physical bodies are immobile. Says Slater, “They will be embodied in that robot, seeing through its eyes, interacting and talking with people, moving through the world.”