HENRY

Out of body experiences have long been a staple of books about alien abductions and things like The X-Files, and they’ve also been reported after certain types of neurotrauma including seizures and drug abuse. Two research groups are reporting today in Science that these can be experimentally induced, by the use of virtual reality helmets. The subjects were wearing helmets that fed video from behind them into the display, so that each person was viewing themselves from a location a few meters behind themselves.

In the first experiment, Lenggenhager et al stroked the backs of the illusory and real subjects. When the stroking of the illusory and real backs was simultaneous, the subjects reported a stronger experience of being outside their body, than when the stroking of their real backs did not coincide with the stroking of their illusory backs.

To follow this up, the experimenters then blindfolded the subjects and moved them around in the room. When asked to move back to their original location, the subjects tended to drift to a location between where their real body had been, and where their illusory body was. The drift towards the illusory body was greater when there had been simultaneous illusory/real-back stroking. Taken together, these results suggest that the strength of the illusion was probably a result of the concurrent experience of visual and tactile stimuli. (More info: abstract of Video Ergo Sum: Manipulating Bodily Self-Consciousness, doi).

In the second experiment, by Ehrsson, the experimenter first simultaneously poked the subject’s real chest and the same location on the “virtual” chest. This meant that the subjects experienced the feeling of being poked, at the same time as they saw their illusory body being poked (I get the same feeling whenever I use facebook). Again - these results suggest that it’s the correlation  between visual and tactile experience that strengthens this illusion.

To track this down further, he measured the emotional response to this by skin conductance,
when the subject’s illusory body was hit with a hammer. When the real body was poked at the same time as an illusory hammer hit, the subject’s conductance response was greater than when the real body poke did not coincide with the hammer hit. This suggests that the people were responding emotionally to this illusory body. (More info: EurekAlert, Abstract: The Experimental Induction of Out-of-Body Experiences, doi).

Posted on August 24th, 2007 by Simon Greenhill