Disowning an arm or a leg despite the fact that it is still attached to the body is a common symptom of stroke, anorexia and schizophrenia. And, curiously, the temperature of these rejected limbs is always low. Now researchers have tricked healthy people into disowning a limb. The work implies a more complex relationship between mind and body than had been thought. The so-called ‘rubber hand illusion’ is induced by stroking a person’s hand while it is out of their sight and at the same time stroking a visible rubber hand. The trick makes the subject perceive the rubber hand to be their own. It was discovered that this feeling is accompanied by reduced blood flow and a drop in temperature in the ‘rejected’ limb. Thus the body tells the thalamus (part of the brain thought to regulate body temperature) what to do.
"The experiment suggests that the conscious sense of who we are is intimately linked to our physical bodies. This is pretty ingenious. They have shown a direct link between body ownership and the physiological system", says Henrik Ehrsson from the Karolinska Institute in Stockholm Sweden.
-New Scientist 30 Aug 08
Through its identification with the physical body, and the inanimate objects used by the body, the ego gives us an illusory sense of being a discrete self (rather than a universal Self).