Illusions: Reflections on the Mind; July / August 2011; Scientific American Mind; by Vilayanur S. Ramachandran; Diane Rogers-Ramachandran; 5 Page(s)

You probably look in a mirror every day without thinking about it. But mirrors can reveal a great deal about the brain, with implications for psychology, clinical neurology and even philosophy. They can help us explore the way the brain puts together information from different sensory channels such as vision and somatic sensations (touch, muscle and joint sense). In doing so, they can reveal a lot about our sense of self. Would a person who has never looked at his reflection—even in a pool—ever develop a sophisticated self-representation?

Using two bricks, or some duct tape, prop up an 18-inch-square mirror vertically on a table. Sit so that the edge faces you. Now put your left hand on the table at the left side of the mirror (either palm up or down) and match your right-hand position on the right side. If you now look into the right side of the mirror, you will see the right hand’s reflection optically superimposed in the same place where you feel your left hand to be. (You may need to adjust the position of the left hand to achieve this sensation.) It will now look like you are viewing your own left hand, but of course you are not. Now try the following experiments.