I had been dating and living with a guy for three years, and he always had a full head of hair and a goatee.

That's Rebecca Watson. She's a YouTuber who does science videos under the name Skepchick.

And one day, he picked me up after work in his car. And I saw the car outside, went and I jumped into the passenger seat, and I turned and looked and I saw a complete stranger sitting in the driver's seat. And I said, "Oh, my God, I'm so sorry. I thought this was my boyfriend's car." I jumped out of the car and it's only when he yelled after me that I recognized his voice and realized that that was my boyfriend. It's just that he had shaved his head and his goatee and, you know, those were the features that made me recognize who he was. And I remember just thinking, what is wrong with me?

Rebecca didn't know it at the time, but she soon found out that she has this unusual condition called prosopagnosia or face blindness, as it's commonly known.

It's going to be pretty much impossible for me to tell you apart from other faces that bear any kind of similarity to your own.

People with prosopagnosia often have to rely on non-facial information like hair color or height to distinguish people. Even people they know well.

I tend to focus on any any strange part of a person's appearance, you know, if they have weird teeth or a big nose or a mohawk or something like that, which I also think is why I don't find conventionally attractive actors attractive. Like, give me a weirdo over anything like the "Chris" actors, Pine, whatever. They all look the same to me. They have -- they do not interest me at all. Give me a Steve Buscemi.

And what she's describing has been a constant struggle with Rebecca's dating life.

I met my current husband at a party. I met him several more times without really logging the information in my brain. And I was out with a friend at a bar. And she said, "oh, I invited Chris to come over." And I said, "who?" And she said, "you remember. Chris" And she showed me a picture on her phone. I was like, "nope, never met him." He showed up to the bar and I said, "hi, I'm Rebecca. Nice to meet you." And he said, "yeah, we've met several times." And I was like, "have we?" He said, "yeah, you know, I was at that party," and I had to tell him like, "look, the reason why I didn't think we had met before was because I have prosopagnosia." People always ask like, how did you guys meet? And I always picture that bar and he always pictures the party.

Think of it like this. When you think of your sight as a sense, you think of annual eye checkups, 20/20 vision, the ability to see the world around you as well as the people you know and love. But what if your inability to recognize people had nothing to do with your eyes? Prosopagnosia is actually a condition that happens in the brain. It's a disorder that impacts about 1 in 50 people, that's roughly 160 million people worldwide. And some can go through their entire lives not really knowing they have the condition, not knowing that other people perceive the faces that populate the world differently. In this episode, we'll explore how people with prosopagnosia see others, and what we can all learn from those who have deficits in facial recognition. I'm Dr. Sanjay Gupta, CNN's chief medical correspondent. And it's time to start chasing life.

Prosopagnosia is a condition that I've been interested in for a long time. I actually did some reporting on it 11 years ago.

The owner of this face is is looking tough, but I don't know who it is.

That's the late neuropsychologist and my friend Oliver Sacks. I was showing him a picture of Elvis Presley.

I can see your expressions and, and your attention and where your eyes look. But I see all of the features but it doesn't it doesn't quite add up to a unique image for me.

So there are people who can do all the standard processing of the face. The can tell you gender, the emotion. They can lip read all of that, but they just can't tell you who the person is. I don't like the term face blindness. I know it's in the vernacular, but the reason I don't like it is because it suggests that these people are blind to the face and they're not blind to the face. They see it, but they don't see it the way you and I do.

That's Ashok Jansari. He's a senior lecturer in neuropsychologist at Goldsmiths, University of London. He researches disorders of human memory and facial recognition, including prosopagnosia. As he said, it's not that people can't see. The problem seems to be in putting all of the different facial features together into a complete face.

If you were to see my face again, you wouldn't think "left eye, right eye, nose, mouth. That's Ashok." You see a whole. And what's gone wrong with these people is that they've lost the ability to see the whole.

Jansari hopes that his research will bring greater insight into the processes behind facial recognition. What makes it tricky is that there's different types, each caused by a different impairment to the brain, some developed and some acquired.

So the acquired is following some sort of brain insult. And the important point is that these people used to be able to recognize faces. The developmental cases are very different. These are people who at the moment, certainly with the current brain imaging techniques, we can't see any abnormalities, brain damage, and yet they have a condition. S,o we have people who can't recognize faces as well, but they've never had any brain damage. So those are referred to as developmental prosopagnosia.

Now, at the moment, there is no known cure for either case of prosopagnosia. Jansari and other researchers are still trying to get a better picture of the neuroscience behind facial recognition. And the way that they're doing this is by comparing those two types.

We're trying to work back to what does that tell us about the normal brain? And the analogy I used is that the cognitive system is a complex jigsaw. For example, Patient A is missing a particular piece that might be in the top right hand corner. Now we meet another patient, Patient B, who's got a very different type of face recognition disorder. And this one tells us what the shape is of the piece in the top left hand corner. By adding up these different pieces of jigsaw that we were finding from individual patients, we slowly move towards an idea of how you and I recognize faces.

I get that there's lots of different, as you say, flavors of of this. But I'm wondering just just sort of more simplistically, is this more of a memory issue or more of a visual issue?

It's more of a visual issue because we know that their memory works fine. Like my patient, David, he knows that there are famous people and he's got some stuff in the hard drive from before his brain damage. And he knows that these bloody psychologists keep showing him pictures of famous faces. So he saw this picture of me from about 18 years ago with the goatee, etc...and I wasn't there. We'd made sure I wasn't there. And we wanted to see just whether he recognized me. But he saw the elements of the face but he miscombined them. When he came to the picture of me. And I wasn't there. My my student was running the study. He said, "yes, I know who it is." And Scott said, "okay, who is it?" Thinking that he'd say, "oh, that's Ashok." And David said: "that's George Michael." And Scott was very professional and didn't laugh his head off. And he said, "on a scale of 1 to 10, how certain are you that that's George Michael? And he said: "10. That's George Michael." And what this tells us is that his memory works because he knows who George Michael is. He's that Greek guy with the goatee, beard and the gold earring.

A lot of people will say, "I'm not good with faces," right? "I'm good with names. I'm not good with faces." They don't necessarily have prosopagnosia, right? I mean, at what point does it become prosopagnosia?

And that's an important research question. And this is where the blurred boundaries between developmental and acquired prosopagnosia come in. For a start, a lot of people say to me when they find out that I work in face recognition: "I'm terrible at facial recognition." People think they're bad with face recognition because they can't remember that person's name. But they don't think that this person is their school teacher when in fact it's their boss. I always talk about the normal distribution of the bell shaped curve, which is everywhere in nature. Every four years we give medals to people who can run faster, swim faster, jump higher, etc.. They're at the extreme right hand of this bell shaped curve because they're faster or better or whatever. Then there's people who are not as good as them, but who are really good, people like ourselves, who are in the middle, we're kind of the average. Then there's the downward slope towards the left, which is worse than average. Now, at some point, we have to draw a line as to what becomes dysfunction. And that's actually a really tricky issue because the fact that I can't run a marathon or run 100 meters in 10 seconds, does that mean I've got a dysfunction? No. Just means I'm not as good as them.

I ask this next question -- I guess some people will think maybe I'm joking, although I'm not. There'll be people who come up to me in the hallways here at CNN and say: "Hey, Fareed, how are you doing?" Okay? So Fareed and I are both Indian and I love Fareed. It's you know, to be called Fareed is a compliment, I think. But but the idea of racial groups, you know, having a harder time identifying people within a racial group. Indians having a harder time identifying people who are white and vice versa. Is that real?

Yeah, it's real, but it's not for the reason that people think it is. It's not to do with racism. It's an expertize issue. So before global travel, etc., people had stayed where they were born and we were in monocultures where everyone around us was from our tribe. So someone in Italy wouldn't have seen other white people who happen to be blond and blue-eyed from Scandinavia because they didn't mix. If you're in a land of blue-eyed blonds, you need to get really good at telling apart this blue-eyed blond from that blue-eyed blond. Telling apart a Nigerian from a Ghanaian, it was like, why would you? You never see Nigerians and Ghanaians. So when you see a Nigerian and Ghanaian and and you you mistake them for one another, you're not being racist. It's just because you haven't developed the expertize to differentiate them because you haven't needed to.

I guess that's reassuring in a way, and it makes sense. You know, I'll tell you a funny story. Fareed would tell me that he would often get called -- he would be mistaken for me as well. And Fareed does all this very academic, very smart reporting on foreign policy. And I had just done a series of documentaries all about cannabis and weed, and people were coming up to me.

Equally important, I think.

I think it's important. But, you know, people are. Back up to Fareed saying, "I really love what you've done with weed, man." And Fareed didn't, he could not understand why everyone kept saying this to him for a while, which I thought was hilarious. Not racist, just hilarious.

Not racist but what I would say is that their own race bias is not a racism. But that doesn't mean that people can't try harder.

It's so fascinating, Ashok. But I got bad news. I'm actually Deepak Chopra. You've been talking to Deepak Chopra the entire time.

I knew that there was something in here that made me feel uncomfortable.

You know, earlier in our conversation, Ashok mentioned the normal distribution of the bell curve when it comes to facial recognition. Some people being okay at it, others being really bad at it. But if facial recognition is a spectrum with prosopagnosia on one end, what does that tell us about people at the other end of the spectrum?

So they're like our "Usain Bolts" who can we can run really fast or recognize faces really well,

Stick around after the break. And now back to Chasing Life.

Prosopagnosia research is still ongoing. There's not much we know about therapies or cures for the condition yet, but each time researchers learn something new about people with prosopagnosia, they get a better understanding of the mechanisms underlying the condition. Now as Jansari said, researchers like him also study those with extraordinary facial recognition abilities: the so-called super recognizers.

Theoretically, we don't we don't yet know what they're really doing, but we think that that configuration, that triangle, they get it straight away. Part of the work in this started when we had civil unrest in London in I think it was 2011.

So you can see the police are running down here in the center of Peckham, trying to reestablish order. But it's a very, very scary atmosphere.

The Metropolitan Police of London, they were looking for 5000 suspects, which they had on CCTV camera, and they just needed to identify who it was. So, what they did is that they they published the photographs between different boroughs of of London, for different police stations. And they asked their officers when they logged in for their duty just to go through today's list. The next thing was that, let's say the average London police officer got three people.

But when it came to the super recognizers.

I worked with one police officer who recognized 183 people. And one of the faces was the guy had a balaclava covering most of his face. The CCTV camera was up on a building looking down and he wasn't even looking up, you know, smiling. It was an oblique angle on the guy's face. We don't know what they're doing, but they're doing something quite special. And just like with the people of the brain damage, we're looking at this "Usain Bolt" end of things to try to triangulate back to how do you and I recognize faces.

While having super recognizers as part of a police force can be very beneficial towards solving crimes, Ashok's research does raise the question of what happens when prosopagnosics happen to have jobs in intelligence services.

Now, the reason that this became kind of important is that if someone is working in a security role which involves facial identity, you'd think that facial identity ability would be important. Like, you know, if if you're going to go for a job as a chef, you'd need to demonstrate that you can crack an egg. But that's never been done in security forces. And there was a study in Australia where they got these border control people to look at someone's passport and a picture of them now because, you know, I don't look like my passport picture because it's a few years old. Are these the same person or not? And they were making 1 in 7 errors. Now on a plane of 250 people, 1 in 7 is a lot. And with global terrorism, that's a lot of potential shit.

In your experience to show how debilitating can this be for somebody?

So if someone was someone who had an optimistic attitude to life, they would just say, "okay, life sucks, I've got this problem, but better move on." For some people, it can be really difficult. For others. They just are very honest about it. My patient, David, basically has said to all his friends, "if I'm about to meet someone, feel free to tell them. I don't mind coming out of the closet on that one." But with the people with the developmental version, I think it is different because their trajectory and their relationship with their prosopagnosia is much more complex. Oliver Sacks talked about prosopagnosia before he realized that he might have it, himself. So there's an awareness issue. Then there's the fact that some people, they realize that they don't recognize faces. It makes them nervous going into a crowded room, you know, parties, work functions, etc. It's like I'm going to insult someone. So for them, there can be a kind of hiding. They can kind of withdraw themselves from things, anything that involves groups. You know, they don't want to be labeled as having a problem. And those are the people I fear for. So, I did want to do more work with kids with prosopagnosia, because ultimately each one of these adults was a kid.

What is the youngest that you've been able to see a diagnosis actually made? I imagine if someone has it developmental, they they have it from from birth. But at what age does it actually start to impact kids?

I think it starts showing probably when they go to senior school. In elementary or primary school, you stay in one classroom. You tend to sit in, on your table with your friends and you're always there through the whole year. So, you've got these kind of you can work out that if someone over there is talking, then it's Jimmy. Now, you can kind of bluff your way through and you might not even realize you've got this problem. You go to a high school or whatever, you move to the teacher. There are different people in each class. People are now, you know, experimenting with different hair and different clothes, etc.. Suddenly those cues that you used to be able to use before 11, they've been taken away from you. So if we can get the message out there that, look, we know you talk about dyslexia, but want that person recognition because some of these poor kids will have that problem as well. And it's going to have those emotional issues later on. I mean, these days, if you've got a thing like dyslexia or ADHD or whatever, you get special compensation, time in for exams, etc., etc., because it's understood and there isn't a stigma attached to it. So I think if we could move that towards things like prosopagnosia, that's going to be really important.

My conversation with Ashok has been really illuminating and it's also got me thinking about the way that we introduce ourselves and the way that we often run with the assumption that everyone's perception of the world is similar to ours. But that just isn't the case. The fact that some people may not even know that they have this, like Rebecca from earlier in the episode or like Oliver Sacks. Well, that's troubling, and it makes me want to make some social changes in my own life. I'm going to try and introduce myself more often because you never know who really experiences this and who doesn't. If you have prosopagnosia or think that you do reach out. There are researchers who are trying to find out more about this condition and they could actually use your help. And if you know someone who has prosopagnosia, something you can do to help them is to let them know before you have a big style change or even a haircut or a shave. Maybe you could dress a little bit more distinctly to make yourself stand out and be more recognizable to that person, especially since there are no known cures. The least we can do is to educate ourselves and others. Grace can be afforded to people in ways that they have not yet experienced. Did today's episode strike at something that may be true in your own life? Are you rethinking your facial recognition abilities or those of a loved one? Let us know. Record your thoughts as a voice memo and email them to ask Sanjay at CNN, CNN.com or give us a call at 4703960832 and leave a message. We might even include them on an upcoming episode of the podcast. We'll be back next Tuesday. Thanks for listening. Chasing Life is a production of CNN Audio. Megan Marcus is our executive producer. Our podcast is produced by Emily Liu, Andrea Kane, Anne Lagamayo, Rafa Farihah, Xavier Lopez, Grace Walker and Eden Getachew. Tommy Bazarian is our engineer. And a special thanks to Ben Tinker, Amanda Sealy and Nadia Kounang of CNN Health, as well as Rafeena Ahmad from CNN Audio.