Dashing for a train in a busy station at rush hour, I picked out a face in the crowd—the familiar configuration of features, the laugh lines and the mole above the right eye. I immediately knew the distinctive visage belonged to my former classmate, Robert.
Most of us are highly skilled at recognizing faces, even though they all have similar features arranged in roughly the same configuration: two eyes separated by a standard-issue nose, along with a mouth, chin and cheeks. We are similarly adept at reading facial expressions to intuit a person’s mood and at extracting information about an individual’s sex, age and direction of gaze. We do this reading within a fraction of a second, an ability that is critically important for normal social interactions.