Monday, 23 Mar, 2009 Science

Virtual Hand Illusion


One of the most stunning illusions was discovered a decade ago by psychologists from Pennsylvania. In an experiment dubbed "The Rubber Hand" they managed to make people believe that a rubber hand lying next to them is their own. They put the rubber hand on a table in front of each participant and stroke it in the same way as the real hand. The experiment was very important in understanding the way our sight, touch and the sense of body position unite to form a persuasive feeling of body ownership, which is one of the basis of self-consciousness.

Recently, in an experiment inspired from the rubber hand illusion, Mel Slater, a professor of psychology at the UPC Barcelona Tech, Spain, was successful in convincing 21 people that a virtual arm, shown on a 3D display, was their own.

In his research Slater showed each study participant a computerized illustration of a right arm. For the experiment the volunteers had to stretch their arm out in front of them. Then the arm was hidden from view. With own arm hidden and a virtual shown on the monitor the participants started thinking that the virtual arm extends from their right shoulder. Just like in the famous rubber hand illusion, the professor touched and stroked each volunteer's real arm with the help of a wand that transmitted images of a virtual wand making the same moves on the virtual arm, informs NewScientist.

At a certain moment the volunteers started feeling as though the virtual arm was really their own. After that Slater turned the virtual arm 90 degrees, thus causing muscle spasms in the right shoulder of each participant, because volunteers had the feeling that their real arm was being rotated.

Currently Slater and his team are looking forward to extend the illusion. Researchers want to make a computer-generated body to feel like the real one and the ultimate goal is to make people feel the virtual world.

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