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When you see a familiar face – a sibling or a close friend – is there any uncertainty prior to that moment of recognition? What about an old schoolmate or someone you've only met once or twice before? Do you sometimes need a few seconds or more to figure out who the person is? Have you ever drawn a complete blank when looking at the face of someone you should otherwise know quite well?

Most people can distinguish one face from another, but the results of a growing number of studies suggest that the ability to visually process and recognize faces is not universal and can vary tremendously from one person to the next. Some may rarely forget a face. But at the other end of the continuum are individuals who may be unable to identify any face, even if it's one of their kids, their spouse or their own reflection in a mirror. This face blindness is formally called prosopagnosia, a term that combines the Greek words for "face" and "lack of knowledge."

Prosopagnosia has long been known to occur as a result of stroke or other brain damage. But scientists now recognize that it can occur even in the absence of any disease or injury. This congenital or developmental form of face blindness can run in families, and occurs with varying degrees of severity in an estimated 2 per cent of the population. Thus, in Canada alone there may be over 650,000 individuals who are seriously impaired in their ability to tell one face from another. And many more may find remembering faces a challenge, even if the problems they experience are not as severe.

A large proportion of the human brain is devoted to processing visual information. Neuroimaging studies have revealed that specific regions within the occipital and temporal lobes are especially responsive to faces. Researchers have yet to fully explain how these areas contribute to face perception. Nevertheless, the occipital face area, near the lower back and side of the brain, appears to be critical for the initial analysis of a face and its specific features. A bit ahead of this is a region in the temporal lobe called the fusiform face area, which seems to be more heavily involved in processing the overall configuration of facial features – the nose in relation to the eyes and mouth – and otherwise representing the identity of a face as a whole.

Recent research suggests that this more holistic processing – seeing the forest instead of a bunch of trees, so to speak – is particularly important when considering individual differences in face-recognition abilities. A growing number of studies have revealed that face blindness is associated with a deficit in holistic processing. And superior face perception and recognition in a more general population has also been shown to be correlated with how strongly an individual displays holistic face processing.



Fortunately there may be hope for those who struggle to figure out if they've met someone before. Researchers have used computerized training over the course of several days to enhance individuals' attention to the overall configuration of facial features. Results suggest that such training in individuals with congenital face blindness can subsequently improve face perception, and enhance the co-ordination of activity between the occipital and fusiform areas.

Mark Fenske, co-author of The Winner's Brain: 8 Strategies Great Minds Use to Achieve Success , is a neuroscientist and associate professor at the University of Guelph.

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