A team of neuroscientists in Sweden have used virtual reality to create the illusion of being invisible in a group of subjects so they could test their psychological reactions. From Plato to HG Wells and JK Rowling writers have speculated about invisibility, what people might do with the power and how they would react. In 2015 however, scientists appear to have cracked the code and actual invisibility technology is on the horizon, so the team felt that it was time to put literary speculation to the test.
A paper in the journal Scientific Reports describes the reactions of 125 subjects to the perceptual illusion of having an invisible body. Participants were asked to stand while wearing a virtual reality head set. When they looked down at their bodies, participants would see the room around them but there was nothing where their bodies should be.
Scientists then stimulated the sense of touch while miming the same stimulation. For example, subjects were touched with a paint brush while another paintbrush imitated the movements of touching in mid-air where it could be observed by the subject.
“Within less than a minute, the majority of the participants started to transfer the sensation of touch to the portion of empty space where they saw the paintbrush move and experienced an invisible body in that position. We showed in a previous study that the same illusion can be created for a single hand. The present study demonstrates that the ‘invisible hand illusion’ can, surprisingly, be extended to an entire invisible body,” said Arvid Guterstam, lead author of the present study in a statement.
The researchers further tested the method by making a stabbing motion with a knife toward the empty space where the invisible body should be. The neuroscientists report that sweat response increased in the participants on seeing the knife. That same reaction did not occur without the illusion.
Participants were also tested for a social anxiety response to standing in front of a room full of strangers.
“We found that their heart rate and self-reported stress level during the ‘performance’ was lower when they immediately prior had experienced the invisible body illusion compared to when they experienced having a physical body. These results are interesting because they show that the perceived physical quality of the body can change the way our brain processes social cues,” said Guterstam.
The researchers hope that the results of their work, in addition to providing insight for the technology of actual invisibility, will aid in the development of new therapies for social anxiety disorders.
“Follow-up studies should also investigate whether the feeling of invisibility affects moral decision-making, to ensure that future invisibility cloaking does not make us lose our sense of right and wrong, which Plato asserted over two millennia ago,” says principal investigator Dr. Henrik Ehrsson, professor at the Department of Neuroscience at Karolinska Institutet.
