Most of us have a powerful ability to recognize faces, and yet we hardly ever take note of it. We can commit a face to memory with a single glance, and even if we see that face only once its memory can stay fresh for years. The faces we remember may differ only in subtle tweaks of geometry: the ratio of distances between the eyes and the mouth, for example.
A small fraction of people, however, cannot recognize faces—even the faces of their parents, spouses, and children. Prosopagnosia, as this condition is known, can affect people from birth or be triggered later in life by injuries to the brain. It strikes an estimated 2 percent of Americans and is often accompanied by other types of recognition impairments, including difficulty recognizing places and objects, such as cars.
Despite the millions of people who suffer from prosopagnosia, it remains an obscure disorder, probably due to the skill with which face-blind people quietly compensate for their condition. In his recent book The Mind’s Eye, neurologist and writer Oliver Sacks makes the surprising disclosure that he has prosopagnosia. “I have had difficulty remembering faces for as long as I can remember,” he writes. Sacks, who turns 79 this year, has been publishing books for four decades. Despite his many years in the public eye, this is the first time most of his fans have learned of his condition.
