Have you ever stopped to consider what a brilliant mind reader you are? If someone in your field of view experiences a sudden happy thought or a wave of anger, you do not need to be told. You just seem to know. Of course, this ability is not based on psychic powers but on the reading of small clues: a distinctive curl of the lips for joy, a clenching of the jaw for pique. Think of how a mime, working without words, can evoke an entire story, with multiple characters, each with their own intentions, beliefs and desires—all because we are remarkably skilled at imagining the mental lives of others.
At the Massachusetts Institute of Technology, Rebecca Saxe, 33, is part of a scientific movement to better understand this ability, known as theory of mind. Saxe established that there is a single location in the brain, the right temporoparietal junction, where this thinking is centered. The finding surprised neuroscientists because theory of mind is an abstract and involved ability, the kind they would have expected to involve large swaths of the cortex. Yet, according to Saxe, this little section of brain, just behind the right ear, drives much of what we associate with humanity—conversation, friendship, love, empathy, morality. And art: theory of mind is why humans write novels and why they read them.