In a fascinating article in the current issue of the New Yorker, Dr. Oliver Sacks reveals his personal life-long struggle with prosopagnosia, or face blindness, a condition he didn’t realize he had until middle age.

Sacks, a professor of neurology and psychiatry at Columbia University and the author of a long string of best-selling books on the brain, writes that he had always known he was very bad at recognizing faces. Yet, not until he visited an older brother in Australia (whom he hadn’t seen much for more three decades) and found that his brother had the same difficulties did it dawn on Sacks “that this was something beyond normal variation [and] that we both had a specific trait, a so-called prosopagnosia, probably with a distinctive genetic basis.”

Earlier this month, I wrote about a study that has gotten under way at the University of Minnesota on children with developmental (or present from birth) face blindness. (Face blindness can also be acquired through injury or disease.) The first child enrolled in that study, a 7-year-old boy, had developed a single friendship in school — with a girl who always wore pink. During his childhood, Sacks used similar types of distinguishing features to recognize classmates and, thus, forge friendships. “I identified particular features: Eric had heavy eyebrows and thick spectacles, and Jonathan was tall and gangly, with a mop of red hair,” he writes.

Sacks describes his prosopagnosia as “moderate.” He is not, however, referring to the run-of-the-mill (and sometimes embarrassing) problem that we all have from time to time of failing to recognize somebody we knew tangentially years ago or met only briefly more recently. (Recognizing people out of context is challenging at times for everybody.) Sacks failed to recognize his personal assistant of six years in the lobby of a Manhattan office building, even when he’d gone there purposely to connect with her before a meeting. On another occasion, he failed to recognize his psychiatrist whom he had been seeing twice a week for several years when he ran into the man in a different setting.

And Sacks’ prosopagnosia extends to himself. “[O]n several occasion I have apologized for almost bumping into a large bearded man, only to realize that the large bearded man was myself in a mirror,” he writes.

Sacks also has topographical agnosia — difficulty recognizing places — which he says often goes hand-in-hand with prosopagnosia. Once, when he went for a walk from his home with a visiting nephew, Sacks couldn’t find his way back to his house or his street. “After two hours of walking around, during which we both got thoroughly soaked, I heard a shout,” he writes. “It was my landlord; he said that he had seen me pass the house three or four times, apparently failing to recognize it.”

In his usual clear, clean prose, Sacks describes how scientists have come to understand what goes on in the brains of people with prosopagnosis (which almost always involves a lesion in a structure called the fusiform gyrus). He also describes some intriguing related conditions. One is Capgras syndrome. People with this syndrome recognize faces, but those faces no longer produce a sense of “emotional familiarity.” “Since a husband or wife or child does not convey that special warm feeling of familiarity, the Capgras patient will argue, they cannot be the real thing — they must be clever imposters, counterfeits,” writes Sacks.

Sacks also discusses “super-recognizers,” people who seem to never forget a face, including the waiter who served them a meal three years ago or the friends of a friend of a friend they met briefly at a social gathering. “[T]he difference between the best face recognizers and the worst among us is comparable to that between people with an I.Q. of 150 and those with an I.Q. of 50,” writes Sack. “As with any bell curve, the vast majority are somewhere in the middle.”

You need a subscription to read Sacks’ New Yorker piece online. But the New Yorker has posted a free 14-minute audio podcast of Sacks discussing face blindness (including his conversations with primatologist Jane Goodall and artist Chuck Close, who also have prosopagnosia) here. Chuck Close recently discussed his prosopagnosia on the Colbert Report, which you can watch here.