[escepticos] Out-of-body experiences are 'all in the mind'

["Pedro J. Hernández"]

*Confirmado una vez más lo que todos ya sabíamos

Out-of-body experiences are 'all in the mind'
*
· 19:00 23 August 2007
· NewScientist.com news service
· Andy Coghlan

By deliberately scrambling a person's visual and tactile senses, it is 
now possible to give them an "out-of-body" experience.
Two procedures – which are the first to imitate an out-of-body 
experience artificially – use cameras to fool people into thinking they 
are standing or sitting somewhere else in a room. They provide the 
strongest proof yet that people only imagine floating out of their 
bodies during surgery or near-death experiences.

"The brain can trick itself, and when it is trying to interpret sensory 
information, the image it produces doesn't have to be a real 
representation," says Henrik Ehrsson, of the Institute of Neurology, 
University College London, UK, who designed the first experiment.
To trick his subjects, Ehrsson gave had them wear a head-mounted display 
that showed them footage of themselves filmed from behind, while 
preventing them from seeing anything else. He then used a plastic rod to 
prod the subject in the chest and simultaneously held a second rod in 
front of the camera behind them, to make it seem that the illusory 
"person" viewed from behind was being prodded in the chest too.
Subjects physically felt themselves being prodded, but also had the 
weird sensation that it was their alter ego in the film footage being 
prodded. "It gives you a very strong sensation you're sitting somewhere 
else," Ehrsson said at a press conference held in London.

*Not madness
*His conclusion is that our perception of self within the body is 
tightly bound to how our brains process information from our senses. 
"I'm not interested in out-of-body experiences," says Ehrrson. "I'm 
interested in why I, as myself, am located in my body – why we have 
'in-body' experiences, if you like."
He says the work is important because it de-stigmatises reports of 
out-of-body experiences by people who are on drugs, or ill with 
conditions such as migraine or epilepsy. "They don't have to be mad to 
experience these things," he says.
Ehrrson's results are echoed by a second out-of-body experiment, 
conducted by Olaf Blanke and colleagues at the Federal Polytechnic of 
Lausanne (EPFL) in Switzerland. This group also deliberately scrambled 
the visual and tactile experiences of subjects to create a sense of 
disembodiment.
In Blanke's set-up, people were fitted with 3D headsets and forced to 
watch virtual "figures" standing two metres ahead being stroked on the back.
They either saw live footage of themselves, of a dummy, or of an 
inanimate black board being stroked. Sometimes the subjects themselves 
were stroked at the same time, and sometimes not.
After watching the images for a minute, the subjects were blindfolded, 
move directly backwards and asked to walk forward to where they had been 
originally standing.

*Relocated self
*Blanke found that those who had seen either themselves or the dummy 
being stroked while also being stroked, overshot their original position 
by 25 centimetres on average, suggesting they were drawn towards the 
"person" they had watched, thinking it was actually them. But the trick 
did not work if they watched the blackboard being stroked, or if they 
had not simultaneously been stroked.
Blanke says the experiment demonstrates that the sight of a human-like 
figure combined with stroking can trick a person into subconsciously 
relocating their sense of self away from where it should have been. "The 
self was no longer within the body borders," he said at the same press 
conference. But he admits that the illusion did not create a full 
"out-of-body" experience like Ehrsson's.
Both researchers say their experiments reinforce the idea that the 
"self" is closely tied to a "within-body" position, which is dependent 
on information from the senses. "We look at 'self' with regard to 
spatial characteristics, and maybe they form the basis upon which 
self-consciousness has evolved," says Blanke.
The researchers add that the procedures could perhaps be used to create 
more realistic avatars in virtual reality computer games. The same 
technology might also be used to enable tasks such as surgery to be 
carried out remotely, linking distant surgeons more realistically to 
remotely-operated surgical tools.
Journal reference: /_Science_/_ (DOI: 10.1126/science.1142175)

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