Courtesy: newscientistvideoWe’ve all seen optical illusions, but this illusion will surprise you like a hammer blow to your thumb. Check out the short video above if you haven’t already now. As Olaf Blanke indicates, up to 75 percent of us are partial to the rubber hand’s cheap mind trick. For this experiment, paintbrushes were used to induce the illusion. But in the context of parlor games and foreign game shows, amateur “experimenters” prefer sending a jolt through their victim’s illusory limb by smacking it with a sledge hammer! Cognitive psychologists aren’t certain what the precise neurological mechanism is behind the trick, but decreases in the temperature of participants’ out-of-view hands have been measured during the illusion. Why? One possible explanation is that there’s no reason to heat something that, as far as our feeling brain is concerned, is not there. A similar trick using mirrors has been employed to reduce phantom limb pain in amputees. The success of these illusions reveals a fundamental disconnection between what we know consciously to be true and what we physically feel. Cognitive psychologists say it makes sense to wire what we see directly into brain systems that produce physical sensation and keep conscious understanding out of the loop since something like the spotting of our hand on a sizzling hotplate is processed much faster than our fully reflective understanding of the event. We’ve all seen optical illusions, but this illusion will surprise you like a hammer blow to your thumb.