Scientists recreate 'Invisible Man'
Volunteers have experienced what it feels like to disappear in an experiment echoing the HG Wells story "The Invisible Man".
Scientists created the illusion using 3D virtual reality headsets that projected an image of empty space when participants looked down at their own bodies.
The trick was completed by stroking each volunteer with a paint brush which in the display appeared to be touching an invisible surface.
Researchers then explored the psychological effects of invisibility - just as HG Wells did in his 1897 novella about a power-mad scientist who makes himself invisible and is eventually driven insane.
The real-life experiment suggested that far from being psychologically damaging, invisibility might prove therapeutic for people suffering from social anxiety disorder.
In the study, the 125 volunteers were each exposed to a socially stressful situation by being made to stand in front of a group of strangers.
Their heart rates and stress levels turned out to be lower when they were first rendered "invisible".
Lead scientist Arvid Guterstam, from the Karolinska Institute in Sweden, said: "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."
Previous studies using similar techniques have shown it is possible to convince volunteers that they own a rubber hand, or even a mannequin's body.
The invisibility illusion involved stroking a region of empty space with one paint brush while simultaneously touching a volunteer with another.
A camera captured the image of the empty space and projected it into the head set, so that the participant "felt" the brush coming into contact with an invisible body.
Mr Guterstam said: "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."
Volunteers reported experiencing a "hollow, transparent body" which felt so real it caused them to break into a sweat when one of the scientists stabbed at the empty space creating the illusion with a knife.
The findings are reported in the Nature journal Scientific Reports.
Principal investigator Professor Henrik Ehrsson, also from the Karolinska Institute, said: "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."