“Participants in a recent psychological study will probably never a look at mannequins \u2013 or their own bodies \u2013 in quite the same way again. Before the study, they knew their ar ms belonged to them and synthetic ones didn \u2019t, simply because seeing is believing. Now they \u2019re not so sure. Researchers at Car negie Mellon University in Pittsburgh asked subjects to keep their eyes on a rubber ar m that was sitting on a table in front of them, With the subject \u2019s left arm hidden from view by a screen, the researchers simultaneously stroked both the rubber hand and the subject \u2019s hand with a paintbrush. Even though they knew their own hand was being stroked behind the screen, nearly all the subjects experienced the same bizarre sensation: they felt the fake hand was actually their own.<\/p>\n
According to Matthew Botvinick, the Ph.D. psychology student who coauthored the study with advisor Jonathan Cohen, awareness of self seems to depend on intricate conversations between the brain and a range of sensory inputs that it constantly receives. If those conversations become garbled by contradictory messages, the brain is even willing to stretch the bounds of where the body ends and the outside world begins in order to draw a coherent picture. \u201c It \u2019s like ventriloquism, \u201d says Botvinick, who was so spooked by the illusion when\u00a0 he tested it on himself that he let out a yelp and threw the fake hand across the room. \u201c In the experiment, when something touches the fake hand, you feel it, so the rubber hand\u00a0 appears to be an object with which you sense. And when there is an object of that kind, it \u2019s usually part of you. That seems to be one basis of self-identi\ufb01cation. \u201d<\/p>\n
To con\ufb01rm that the subjects were experiencing a true shift in their perception of themselves, researchers asked them to run their right index \ufb01nger along the underside of the table until it was directly under neath their left one. Those who had experienced the rubber-hand illusion invariably missed their real \ufb01nger altogether and pointed more closely to the fake hand. \u201c When you look at your hand, it doesn \u2019t feel as if your brain might be going through all kinds of complicated computations to arrive at the conclusion that this thing is yours, \u201d says Botvinick. \u201c You just know it \u2019s your hand. \u201d \u2014Jennifer V n Ezra, in the column \u201cNexus\u201d in Equinox, no. 99 (July 1998), p. 14.”<\/p>\n