What do we know about ourselves and our consciousness? We can at least be sure of one thing – that is, we have a physical body in which our consciousness resides, and that we are here and now and nowhere else. But even this can be challenged by an out-of-body experience: an experience during which an individual feels to be outside of his own body, which can be accompanied by the feeling of seeing oneself from a distance. The out-of-body experience (OBE) can be a part of a near-death experience, and is found in some individuals with certain neurological conditions, and it can also be induced by the drug ketamine. But this out-of-body experience can also be induced in perfectly healthy humans; as Henrik Ehrsson (2007) has shown.   

Henrik Ehrsson (2007) made use of a perceptual illusion that evoked an out-of-body experience in healthy patients. In his experiment, a participant sat down on a chair and wore goggles that were connected to two video cameras placed behind his back. The video cameras replaced the visual perception of the subject; the left camera would project the image to his left eye, and the right image would project the image to his right eye. In this way, the person would see his body from the perspective of a person sitting behind him.  Henrik Ehrsson would then stand behind the body of the participant, and then touch his real torso with a plastic rod (which was out of sight), and also the chest of the illusory body by placing another plastic rod just below the cameras. The person still felt that he was in the position of the onlooker, looking at his back. To verify and objectify the illusion of an out-of-body experience, Henrik Ehrsson (2007) also measured skin conductance response (SCR) arousal in a similar experiment. SCR measures emotional or physiological arousal, and should increase when we feel to be “hurt”. Henrik Ehrsson proved that the SCR of participants increased when their illusory body was visually hurt by the beating of a hammer; it increased more after the illusory body (which was visible to the participant) and the real body (which was invisible to the participant) were hit alternatingly – the illusory body received less hits in the second, and therefore the SCR was lower than when the illusory body received all hits.

Thus it was proven that in this experiment the participants' center of awareness – their ‘self’ – was experienced to be located outside of their body, and that they perceived their body from the perspective of another person. Henrik Ehrsson even participated in the experiment himself, and confirmed that the experiment really evoked the feeling of sitting somewhere else in the room, looking at yourself, and while you know this is yourself, it doesn’t feel like yourself; no matter how hard you try to convince yourself (Macrae, 2007). He concluded that the feeling of inhabiting your body is really only determined by perceptual processes – visual perception combined with sensory stimulation of the body. What really matters for your bodily self-awareness is “first-person visual perception” (Macrae, 2007); where are eyes are determines where we locate ourselves. 

What consequences do these kind of experiments have for our notion of consciousness, when our bodily self-consciousness can be fooled so easily? Ramachandran and  Rogers-Ramachandran (2010) even argued that “the sense of ‘owning’ your arm is not fundamentally different [from the sense of inhabiting your own body]—in evolutionary and neurological terms—from owning your car”. Does the out-of-body experiment strengthen the argument for a neural basis of consciousness? If so, is our consciousness fully dependant on perception?

Sources

Henrik Ehrsson, H. (2007). The Experimental Induction of Out-of-Body Experiences. Science, 317, 1048.

Macrae, F. (2007, 24 August). Out-of-body experiences explained away by scientists. Daily Mail. Retrieved from http://www.dailymail.co.uk/news/article-477343/Out-body-experiences-explained-away-scientists.html

Ramachrandan, V., and Rogers-Ramachandran, D. (2010, May). Hey, Is That Me over There? And other real-life tales from the bizarre realm of out-of-body experience. Scientific American Mind. Retrieved from http://www.scientificamerican.com/article.cfm?id=hey-is-that-me-over-there