Submitted by Mark Esposito, Guest Blogger
Think reality is self-evident. Neuroscientists at Stockholm’s Karolinska Institutet aren’t so sure. Seems recent testing reveals it is quite easy to convince the human mind that it’s body has three arms.
A February article in the online journal, PLoS ONE, reports on a study in which participants were asked to test the “supernumerary hand illusion.” The subjects were asked to place their right hand on table and a prosthetic rubber arm was placed next to it. The left arm was hidden from view by a screen. A drape was placed over the right shoulder so that only the forearms of the real and prosthetic arm were visible.
When a paintbrush was applied to the index finger of the real and the fake arm, the subject noted “feeling” sensation in both the real and the fake arm. They even noted the sense that both the real and fake arms were attached to their bodies. A similar result was obtained when a knife was place close to both arms in a simulated threatening gesture.
“Our study shows that the human brain has the ability to experience an extra third arm,” says Arvid Guterstam, the study’s lead author and a neuroscience doctoral student. You might think that being born with two arms and two legs would limit your body image to this idea, he says. “But within less than a minute, you can fool the brain into believing it has an extra arm, which is quite fantastic.”
Besides being “fantastic” the study holds promise for developing new artificial limbs and helping stroke victims who’ve lost the use of a limb. It might also explain why so many seemingly reasonable folks watch Glen Beck. Self-delusion, it appears, has a genetic origin.
~Mark Esposito, Guest Blogger