The condition called "face blindness", but those who have it see perfectly fine. It's just that they can't process what anyone looks like even members of their own family. Dr. Sanjay Gupta has more in the second part of this series Mysteries of the Brain. He joins us from Atlanta. This is so fascinating, Sanjay, tell us about it.

Yeah, it really is very interesting. It's called prosopagnosia, most people do not know the face blindness like you said. Look, we've all had times when we forget a name, maybe we forget a face. But this is truly a medical condition as we learned, it can be very debilitating.

Glenn has spent his entire life forgetting faces.

Most people expect that you are going to be able to recognize them in label. / I can't really do that very effectively.

His condition is called prosopagnosia, or more commonly, face blindness. It can cause problems even identifying close family members or remembering a face just moments after turning away from it.

Glenn, whose case is more severe than most, often can’t recognize his own face.

One of the reasons that I grew out the beard, and one of the reasons that I walk around with my hats so much is to hopefully prevent me from walking into mirrors.

His condition also affects his job at a retail store. He says he won’t get promoted, because he can’t recognize his co-workers. More troubling, his inability to recognize others in social settings drives him into isolation.

I feel like, you know, it will be really nice if I could go out do this kind of thing with a bunch of other people and not be so worried about the difficulties.

Glenn's face blindness is the result of a head injury he suffered as a toddler. But many others are born with the condition. And it's not that rare. At 2006, Institute of Human Genetics study found as many as one in fifty people have some form of face blindness. Researchers still can't pinpoint the cause, but say it's most likely linked to an area of the brain called the fusiform gyrus, which shows activity in response to seeing faces.

Now that we know that prosopagnosia is much more common, I think there is gonna be much more effort to figure out how to help these people.

Blind to the faces of others, still seeing the face, the eyes…

There is no medical treatment for face blindness yet. But Glenn has a message.

Be consoled, because, though I may not remember your face, I will remember you.

This is a remarkable thing, you know. You talk a lot about children as well, who might have this sort of problem, they can't recognize other kids in the playground; they grow up with this condition, sometimes not being able to recognize your spouse either. One woman told us that in fact, she is in a crowded room and looks at a mirror with a bunch of face, she has to make a funny face like raising eyebrows to recognize her own face, so pretty remarkable, Alina(这里应该是女主播的名字).

Oh, My Gosh, this is incredible. I'm, I am curious, Sanjay. Is there any way for them to recognize other people, I mean, for instance, like with blind people, maybe there is voice recognition and, you know, you hear a familiar voice, you might not see their face, but you know who they are, so is there a way for them to do that?

Yeah, you know, it's, it's pretty remarkable. First of all, you give them an eye test, their vision is perfectly fine. There appears to be something in the way that the face, specifically the face is actually processed the way we've evolved as human beings can't recognize the face, but can recognize the objects, can recognize er, voices as you pointed out also recognize hair colors, specific distinguishing features that act as cues to let them get through the day. It can be debilitating but people seem to cope just by finding these cues.