New findings from researchers at Harvard and elsewhere suggest that a surprising number of people are face-blind, so bad at recognizing faces that they routinely snub acquaintances and have trouble following movie plots. In extreme cases, they may greet siblings as strangers and struggle to discern which child is theirs at school pick-up time.

The syndrome, known medically as prosopagnosia, was long thought to be a rare neurological curiosity that resulted from brain damage.

Research has begun to suggest that most face-blindness stems from genes, rather than brain injury, and that it is far more widespread than previously suspected, with up to 2 percent of the population affected to some degree.
—Carey Goldberg, "When faces have no name," The Boston Globe, June 14, 2006

Cecilia Burman has always had a problem with faces. As a child, she struggled to pick out her own face in school photos, and she is hard-pressed today to describe her mother's features. Over the years she has offended countless friends, passing them on neighborhood streets or in office hallways like strangers. "People think I'm just snobby," says Burman, 38, a computer consultant in Stockholm. "It makes me really, really sad to lose new friends because they think I couldn't bother to say hello."

There's a name for Burman's condition: prosopagnosia or, more informally, face blindness. The disorder was thought to be exceedingly rare and mainly a result of brain injury. Until a few years ago, there were perhaps 100 documented cases, says Ken Nakayama, a professor of psychology at Harvard. But last month a team of German researchers took the first stab at charting its prevalence, and the results, published in the American Journal of Medical Genetics, were remarkable. The new study showed that prosopagnosia (from the Greek prosopon for face and agnosia for ignorance) is highly heritable and surprisingly common, afflicting, in some form, about 1 in 50 people—more than 5 million in the U.S. alone. "That's huge," says Dr. Thomas Grüter of the Institute of Human Genetics in Münster, an author of the paper and himself a prosopagnosic. "It was a real surprise."
—Sora Song, "Do I know You?," Time, July 10, 2006

I was born with a condition that makes it difficult for me to recognize faces. There is a small part of the brain that is dedicated to that job, and though it is small, when it comes to recognizing faces, it is very very good. In me, that part doesn't work, making me blind to all but the most familiar of faces.
—Bill Choisser, "Bill's Face Blindness Pages," January 1, 1997