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Swedish scientists create three arm illusion

Swedish scientists create three arm illusion

Published: 24 Feb 2011 08:37 GMT+01:00
Updated: 24 Feb 2011 08:37 GMT+01:00

Scientists working at Karolinska Institute in Stockholm have demonstrated how to fool the brain into thinking that the body has three arms.

The scientists were able to make healthy volunteers believe that they had an extra appendage by stroking the subject's right hand and a prosthetic rubber hand with two small brushes, synchronizing the strokes as perfectly as possible.

"What happens then is that a conflict arises in the brain concerning which of the right hands belongs to the participant's body," said Arvid Guterstam, one of the scientists behind the study in a statement.

Guterstam argued that the expectation was that that the brain would select only one of the hands as the body's own, presumably the real arm.

"But what we found, surprisingly, is that the brain solves this conflict by accepting both right hands as part of the body image, and the subjects experience having an extra third arm."

The team designed the experiment to test the classical question in psychology and neuroscience of how we experience our own bodies and their findings have been published in online scientific journal PLoS ONE.

In order to prove that the prosthetic arm was truly experienced as a third arm, the scientist 'threatened' either the prosthetic hand or the real hand with a kitchen knife, and measured the degree of sweating of the palm as a physiological response to this provocation.

The results demonstrated that the subjects had the same stress response when the prosthetic hand was threatened as when the real hand was, but only during the periods when they experienced the third arm illusion and not, for example when the prosthetic right arm was replaced with a left arm or a prosthetic foot.

The study involved 154 healthy volunteers and it is hoped the results may help to create new applications in prosthetics research.

"It may be possible in the future to offer a stroke patient, who has become paralysed on one side of the body, a prosthetic arm that can be used and experienced as his own," said Henrik Ehrsson at the Department of Neuroscience.

"It is also conceivable that people with demanding work situations could benefit of an extra arm, such as firemen during rescue operations, or paramedics in the field."

The Local/pvs (news@thelocal.se)

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Your comments about this article

09:48 February 24, 2011 by UScitizen
"It is also conceivable that people with demanding work situations could benefit of an extra arm"

Or fika and work at the same time!!!
10:02 February 24, 2011 by Luke R D
Or fika and fika at the same time!!! :-D
11:43 February 24, 2011 by riose
Older than dirt.

In youtube, watch?v=TCQbygjG0RU
12:46 February 24, 2011 by wenddiver
Does it work on non-swedes?
13:22 February 24, 2011 by TIMBER
Its nice to know that the scientists are checking this important work..........
13:42 February 24, 2011 by philster61
Yet another illusion created by Sweden
14:29 February 24, 2011 by Swedesmith
Could you do the same thing with my paycheck?
08:46 February 25, 2011 by loudasthunder
Can they do the same with other body parts?

It sure would make it easier to multitask : )
17:27 February 25, 2011 by jacksonjerry
Come onnnnn.. this is not newwwwwwww.. this is sooooooo oooooooooold...

search in the internet..

search in youtube..
03:38 February 26, 2011 by mfritz0
Yes, apparently this goes much farther than just appendages. Individuals equipped with stereo-vision goggles with computer generated graphics that simulate reality can actually experience out of body experiences relative to the graphic images presented in the goggles. The minds concept of reality is easily fooled. With that said, scientists studying m-theory have determined that there are eleven dimensions to reality with time being the eleventh dimension. Our mind can only comprehend three of these dimensions (length height and width, relative to time) This means that the other dimensions are probably there, but our minds have been fooled into not detecting them.
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