A woman in her sixties, whom I will call Elsa, sought help at my memory clinic. Detailed questioning revealed that her main problem was difficulties recognizing faces. Elsa lived in a small village and could discriminate tourists from local residents (different clothing, language etc.). She was also often able to recognize people from their non-facial characteristics (e.g., voice, hairstyle, laughter, context). She avoided going to the store and other public places as she was afraid she would ignore people she knew. She found distressing that she could no longer follow films and detective programs on TV as she never recognized the characters by sight. Elsa´s medical examination revealed that she had atrophy, or loss of brain tissue, in both temporal lobes, somewhat more on the right side. Neuropsychological assessment did not show any significant cognitive impairment other than the problems recognizing familiar faces. In particular, she did not have any problems with visual perception and could easily discriminate photographs of very similar faces. Elsa had all the characteristics of pure prosopagnosia.
Prosopagnosia was first described in the 19th century but first named by Bodamer in 1947. It has now become relatively widely publicized, probably because of Olivers Sack´s book The man who mistook his wife for a hat. However, a prosopagnosic would never claim that a face is a hat or another object, or an animal. The prosopagnosic knows that he is looking at a face and sees the face perfectly well. He may even know that he is looking at the face of a young woman or a middle-aged male. He just does not recognize it. The term face blindness that is sometimes used for this condition is unfortunate as this disorder has nothing to do with poor vision and the patients are certainly not blind.
The causes of prosopagnosia
Prosopagnosia can be both acquired and congenital. Acquired prosopagnosia can for example be caused by stroke, traumatic injury and degenerative disease (i.e. dementia). It is quite rare and neuropsychologists do not meet many individuals with prosopagnosia during their careers, unless they study this disorder in particular.
Congenital prosopagnosia is, however, more common than previously thought and studies have demonstrated that its prevalence is around 2 – 2.5%. This means that around 2 out of every 100 healthy people have not developed normal ability to recognize faces. This is probably a hereditary condition. For a social animal like humans this must be quite a handicap and congenital prosopagnosics have to learn to compensate for the deficit in various ways. Do you know people who always seem a bit absentminded in a crowd, or never say hello unless you greet them first? Perhaps they have problems recognizing faces…..
Although much has been learned about prosopagnosia we still do not know the full story. Do we, for example, really have a neural circuitry that is committed to recognizing human faces or does the circuitry also allow us to distinguish between similar items within other perceptual categories? My patient, Elsa, who had been a dog breeder, did not only have problems with human faces. She also had difficulties recognizing various dog breeds.
Living with prosopagnosia
Here is an interview with the eminent neurologist Oliver Sacks who has prosopagnosia. You might, at least at first, find his description somewhat amusing. However, try to imagine what it must be like not to recognize the face of your spouse or your children. Or even a photograph of yourself!
Prosopagnosia on film
I know of one full-length movie (Faces in the crowd) whose central character, Anna, has prospopagnosia following an attack. The movie is not entirely neuropsychologically accurate. Perhaps you will pick up the flaws after reading my post and watching the interviews above. However there is some suspense. After all, it must be quite disconcerting to know that someone is out to get you and never knowing whether he is standing next to you or not.
There is also a short film, Prosopagnosia, (about 17 minutes long) that you can watch on-line
In my next post I will tell you what is known about the anatomical basis of prosopagnosia.
Kennerknecht, I., Ho, N.Y., & Wong, V.C. (2008). Prevalence of hereditary prosopagnosia (HPA) in Hong Kong Chinese population. American Journal of Medical Genetics Part A 146A, 2863–2870