Christie's Images/Corbis

Have We Met?

We all know that sinking feeling that comes when we just can't remember someone who clearly recognizes us. So imagine how uncomfortable life might be for a person incapable of recognizing anyone--even a close friend or relative--by face alone. Preliminary results from a recent survey suggest that up to 2% of the general population may be afflicted by this condition, known as prosopagnosia or face blindness.

Developmental prosopagnosia, in which an individual has face blindness apparently from birth, was thought to be extremely rare. The first case, in fact, wasn't diagnosed until 1976. But cognitive neuroscientists Bradley Duchaine of University College London and Ken Nakayama of Harvard University say the condition may be far more common than believed.

Duchaine and Nakayama decided to use the Internet to measure the prevalence of the condition. They recruited individuals for a barrage of psychological tests, including an online facial recognition survey. Some 1600 participants were first given a relatively easy task. They were "introduced" to an individual's face with pictures flashed on screen for 3 seconds, then presented with three additional photos--one of the prior person and two of other people--and asked to choose the person they had seen before. More difficult tests followed, in which participants were introduced to more faces and then presented with pictures of the same individuals but in different poses in different lighting.

The researchers announced in a press release this week that 2% of their subjects had serious enough problems with face blindness that their daily lives would likely be affected. "Some people become socially reclusive, and some lead extremely regimented lives" to avoid bumping into someone unexpectedly, says Duchaine. "It's a neglected condition." The researchers say they have some evidence that prosopagnosia may run in families, but the neurological cause remains unclear.

"For many years, prosopagnosics were the Ivory Billed Woodpecker of neurological patients--they were rare, and some researchers even doubted that they existed," Martha Farah, a cognitive neuroscientist at the University of Pennsylvania in Philadelphia. "Now it turns out that a certain fraction of the healthy population has prosopagnosia." Cognitive scientist Nancy Kanwisher of the Massachusetts Institute of Technology in Cambridge, who has worked on brain scans of prosopagnosics, calls the new findings "really fascinating." She notes that "an ongoing mystery of developmental prosopagnosia is that these people have apparently intact face recognition areas in the brain."

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