Carnegie Mellon researchers open window into the ability of humans to recognize faces

PITTSBURGH--Recognizing faces is effortless for most people, and it's an ability that provides great evolutionary and social advantages. But this ability is impaired in people who have suffered brain damage or in those with a rare congenital condition, and research by Carnegie Mellon University psychologists reveals startling insights into how the brains of those individuals operate. Psychology Professor Marlene Behrmann and postdoctoral associate Galia Avidan have found that people with congenital prosopagnosia--in which their ability to recognize faces is impaired from birth--are not just deficient at recognizing individuals they know, but they are also poor at simply discriminating between two faces when presented side by side. The researchers also have discovered through functional Magnetic Resonance Imaging (fMRI) scans that, contrary to their expectations, the regions of the brain that are activated when normal individuals perceive and recognize faces also are activated in individuals with congenital prosopagnosia (CP). Behrmann and Avidan will summarize the results of their findings in the April issue of the journal Trends in Cognitive Sciences.

"This now presents a large scientific challenge. Given that the impaired behavior in those individuals with prosopagnosia is a function of the brain, we need to identify the neural system that has given rise to this altered pattern of behavior," Behrmann said. "The detective work is well under way."

Unlike the acquired form of prosopagnosia--which results from brain damage such as that suffered in a stroke--congenital prosopagnosia can go undetected, as the person has no means of comparison with normal face processing skills. This can have socially debilitating consequences, and on occasion children with this condition have been misdiagnosed as having autism.

"The potential ramifications of CP are best captured in the words of one individual whom we have had the opportunity to test: 'I have always been a rather extreme introvert, uncomfortable in groups of people and in social activities. I sort of tend to want to be a hermit. However, I find it relaxing to go window-shopping in a mall. A crowd of a hundred strangers is more relaxing than a dozen neighbors whom I know,'" Behrmann said.

Behrmann and Galia said that much remains to be learned from the individuals in their research. They have begun to examine the anatomical details of the brains of their participants, and preliminary findings show that some brain structures are smaller in the region known to control face recognition. Congenital prosopagnosia seems to run in families, which suggests a genetic basis, although that is not true in every case and Behrmann cautioned against calling the condition a genetic disorder. Unfortunately, a cure for the disorder is unlikely to be found anytime soon.

"The work on CP is in its infancy and we still need to understand the psychological and neural aspects of the disorder in detail. It is possible, however, that some forms of intervention may become possible in the near future," Behrmann said.

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