I sat in a restaurant as two young men came in the door and sat down two tables away. One sat with his back to us, the other nodded and smiled at me. I nodded in reply and tried desperately to arrive at the identity of this young man. Could it be a past classmate, or a friend from the gymnastics club?

I was dumbfounded and decided that it was simply a friendly man. But over the course of the next few minutes, the stranger repeatedly looked over to me and smiled. I then examined his face again, more exactly, and was shocked. It was my brother with whom I had spoken just one hour before at our home.

Known since 1947
Such a situation is unimaginable for most people. All of us, of course, sometimes have difficulty to recognize our new neighbors or the clerk at the counter of the flower shop. But not being able to recognize even our closest friends and family members seems impossible.

Even I had until now always been able to recognize my family. It is true I have always had some problems recognizing the faces of new friends but up to a year ago I had put that jokingly down as a "gene defect" inherited from my father, who, like his father, had always had problems with faces. It was not until I was tested by researchers at the University of Münster that I learned that my not so serious self diagnosis was actually correct. They verified that I suffer from a condition called Prosopagnosia.

The German neurologist Joachim Bodamer layed the foundation for research on Prosopagnosia. In 1947 he described the symptoms of three patients who, following a brain injury, could no longer recognize medical personnel, and some relatives, from their faces. Bodamer named the phenomenon Prosopagnosia after the Greek words prosopon, meaning the face, and agnosia, meaning non-recognition.

The term "face blindness" is a misnomer and actually describes only those individuals who cannot recognize a face as such. "There are such cases but they are extremely rare," comments Ingo Kennerknecht of the University of Münster. Prosopagnosia sufferers can recognize faces as such and can even determine the sex and emotional state of a face with little difficulty. They have problems, however, to remember faces and need also a longer time to recognize them.

More often than expected
There are two forms of Prosopagnosia. The acquired form occurs following some kind of brain injury such as trauma to the skull or a stroke. The congenital form of the disease results from genetic factors and is inheritable. Up until a few years ago the disease was considered very rare as most sufferers were not even aware that they had the condition. From a very young age, they learned to use characteristics other than the face to identify other individuals. I had always believed, for example, that all people had to memorize faces in order to recognize them again at a later time and was frequently amazed at the ability of my friends to easily understand the plots of movies while I was constantly mixing up the identities of the actors.

Based on surveys of middle school and university students in the Münster area, Kellerknecht and his colleagues estimate that about 2.5% of the population suffer from Prosopagnosia. In Switzerland, that works out to be almost 150,000 affected individuals - many in the same family since about 50% of the children of people with Prosopagnosia are also face blind.

According to Kennerknecht, a single gene defect would be enough to cause the disease but unitl now, the gene or genes responsible have not been identified. The researchers are hopeful of more insight from ongoing genetic analyses of affected individuals and families.

For everyone a friendly greeting
There is no therapy for Prosopagnosia. The affected individuals must learn to live with their disability. However, they are quite well integrated into society, notes Kennerknecht. Most sufferers, in any case, see no reason why they should look into the faces of those with whom they converse. Some do anyway, though, just to be polite.

In children, Prosopagnosia can lead to social isolation because integration into the classroom social system lasts longer than for other children. They learn over time, however, to overcome the difficulties and, over the years, adopt various strategies to recognize people. For example, when I meet a new individual I try to impress upon myself the form of their hairline or their eyelashes and ears, a scar, teeth, hands, voice or gait.

But even these attempts can go awry: even though I worked for months with my previous boss, I was unable to recognize him one morning because he had styled his hair differently. To be on the safe side there is just one solution - always give people a friendly greeting because you never know who may be standing in front of you.

Information:
http://humangenetik.klinikum.uni-muenster.de/prosopagnosie/
http://www.prosopagnosie.de