To scientists, the simultaneous simplicity and complexity of mirrors make them powerful tools for exploring questions about perception and cognition in humans and other neuronally gifted species, and how the brain interprets and acts upon the great tides of sensory information from the external world. They are using mirrors to study how the brain decides what is self and what is other, how it judges distances and trajectories of objects, and how it reconstructs the richly three-dimensional quality of the outside world from what is essentially a two-dimensional snapshot taken by the retina's flat sheet of receptor cells. They are applying mirrors in medicine, to create reflected images of patients' limbs or other body parts and thus trick the brain into healing itself. Mirror therapy has been successful in treating disorders like phantom limb syndrome, chronic pain and post-stroke paralysis.
"In a sense, mirrors are the best 'virtual reality' system that we can build," said Marco Bertamini of the University of Liverpool. "The object 'inside' the mirror is virtual, but as far as our eyes are concerned it exists as much as any other object." Dr. Bertamini and his colleagues have also studied what people believe about the nature of mirrors and mirror images, and have found nearly everybody, even students of physics and math, to be shockingly off the mark.