A、Detecting one’s facially expressed emotions. B、Determining one’s gender from one’s face. C、Judging a person is pretty or not f

Some people never forget a face. Heather Sellers never remembers one. She finds it almost impossible to recognize people simply by looking at them. She remembers the books she reads as well as anyone else, but movies and TV shows are impossible to follow because all of the actors’ faces seem so similar. She can recall a name or a telephone number with ease, but she is unable to remember her own face well enough to pick it out in a group photograph. Dr. Sellers, a professor of English at Hope College in Holland, Mich., has a disorder called prosopagnosia, or face blindness, and she has had it since birth. "I see faces that are human," she said, "but they all look more or less the same. It’s like looking at a bunch of dogs: some may seem a little older or smaller or bigger, but essentially they ail look alike."
    Face blindness can be a rare result of a stroke or a brain injury, but a study published in the July issue of American Journal of Medical Genetics Part A is the first report of the prevalence of a congenital or developmental form of the disorder: The researchers say the phenomenon is much more common than previously believed: they found that 2.47 percent of 689 randomly selected students in Miinster, Germany, had the disorder. Dr.Gruter is himself prosopagnosic. His wife and co-author, Dr. Martina Gruter of the Institute for Human Genetics of the University of Munster, did not realize he was face blind until she had known him more than 20 years. The reason, she says, is he was so good at compensating for his deficits. "How do you recognize a face?" she asked. "For most people, this is a silly question. You just do. But people who have prosopagnosia can tell you exactly why they recognize a person. Thomas consciously looks for the details that others notice unconsciously." Dr. Thomas Gruter’s experience in this respect is typical of people with face blindness. They develop alternate strategies for identifying people —they remember their clothes, manners, gait, hairstyle or voice, and by using such techniques, many can compensate quite well. "Until very recently, not remembering faces was not considered to be a medical condition," Dr. Thomas Gruter said. "It was not even known to most physicians as such. The term ’prosopagnosia’ was not taught to students of medicine or psychology." Most people "would consider it a bad habit," he said, "much like forgetting the names of people you are introduced to, or being unable to find your way around town." Dr. Martina Gruter said many considered her husband and his father, who is also face blind, to be simply "absent-minded professors" who occasionally may net recognize someone because they are preoccupied with higher thoughts. People with face blindness can typically understand facially expressed emotions --they know whether a face is happy or sad, angry or puzzled. They can detect subtle facial cues, determine gender and even agree with everyone else about which faces are attractive and which are not. In other words, they see the face clearly, they just do not know whose face they are looking at, and cannot remember it once they stop looking. Even familiar faces can be unrecognizable. Dr. Sellers, for example, said she could summon no picture in her mind of her own mother’s face. Dr. Sellers discovered her own problem only a year ago, at the age of 40. She was doing research for a novel involving a character with schizophrenia. "I kept coming across the term ’face recognition’," she said. "It kept ringing a bell, although the phenomenon is quite different for people with schizophrenia. But once I had the term, I searched for it on the Internet. The minute I knew the concept of face blindness existed, I knew I had it." The phenomenon has been investigated with functional MRI brain scans, a form of imaging that shows in real time which parts of the brain are active, and it is known that a part of the brain called the fusiform gyms responds much more strongly to faces than to other objects. Researchers have detected differing responses in this part of the brain among people with face blindness compared with normal subjects. "If you show a normal person two different faces in a row," said Bradley Duchaine, a lecturer in psychology at University College London, "their brain response is different with each one. With some prosopagnosics, you don’t see this different response. It looks like something is not working in those areas of the brain involved with faces." Face blindness is sometimes accompanied by other problems, especially difficulty in finding one’s way around or, for example, distinguishing one car or dog from another.