NEW YORK (Reuters Health) - Millions of people may unknowingly suffer from a little-known disorder, prosopagnosia or face-blindness, according to research funded by the National Institutes of Health.
Characterized by the inability to recognize faces or to distinguish one from another, the condition can be embarrassing and socially disabling.
People with severe prosopagnosia may fail to recognize family members or close friends, or mistake complete strangers for acquaintances. Some face-blind people have trouble watching television shows or movies because they can't keep track of the characters.
As part of their research into prosopagnosia, Dr. Ken Nakayama and Richard Russell at Harvard University in Boston, and Dr. Bradley Duchaine at University College London, UK, developed a diagnostic test and related website (www.faceblind.org), which led to the identification of hundreds of face-blind individuals over the past several years -- far more than had identified previously.
"Until a few years ago, only 100 cases of prosopagnosia had been documented worldwide, but it now appears that the condition is much less rare than had previously been assumed," Nakayama said in a university statement. "Testing of 1,600 individuals found that 2 percent of the general public may have face-blindness and a German group has recently made a similar estimate."
There are two types of prosopagnosia - acquired prosopagnosia and developmental or congenital prosopagnosia. To date, most documented cases of prosopagnosia have been the acquired form, stemming from a brain injury or stroke.
"Probably the reason why these cases came to light," Russell told Reuters Health, "is that these were people who had normal face recognition and then there was some clear incident and after which they could not recognize faces and so the impairment was very obvious to them."
"But we think developmental or congenital prosopagnosia is much more common," Russell said. People with this form of the disorder have no apparent brain damage, "but for most of their lives they haven't been able to recognize faces well," Russell explained, "and until they are given a test, they may not realize they have the disorder. It's like color-blindness; many people don't know they are color blind until they are tested."
The test the researchers developed involves looking at a series of pictures of objects such as cars, tools, guns, houses, and landscapes, along with close-up cropped black and white pictures of faces. Some of the images are repeated in cycles and some are not. Subjects are asked to identify, as quickly as possible, whether each image they see is new or repeated.
Prosopagnosics who take these tests fail to recognize repetition among faces in the series, but they can easily identify repeated pictures of objects.
Think you may have the condition? Completing a questionnaire available at www.faceblind.org will give you a "pretty good sense" of how likely you are to have prosopagnosia, Russell said. At the moment, the diagnostic test for the disorder is not available online, but that's one goal, Russell said.
There aren't any treatments for face-blindness. "Right now we are at the stage of trying to understand what prosopagnosia is and raise awareness about it in the medical community and public at large," Russell said.