oh hey smart people I was just you know self eing on the Google Arts and Culture app it finds your face in famous artworks your art doppelganger if you will mine is I'm not sure but this made me wonder why do some faces look the same to us and how do we even recognize faces I mean there's nearly 8 billion people on earth does someone else have your face every day as you scroll through social media you see dozens maybe hundreds of faces your brain analyzes them and matches them to an identity without you even consciously thinking about it but what would you do if you were scrolling through Instagram and saw your own face this is a man degree this is not Amanda green and this is Amanda green again I'll let her explain a couple years ago I found my look-alike and it was the strangest but most exciting thing that's probably ever happened to me and now I have a great story to tell at parties a friend of Amanda's saw a picture online that looked like her but it wasn't Amanda it was someone who shared Amanda's face after she posted the photos the internet found her doppelganger a girl named Meredith from Indiana who Wow looks exactly like her at least I think so I think it's when it was trending in second place on BuzzFeed like under Kim Kardashian but I was like this is really bizarre but after Amanda and Meredith's photos went viral some people argued that they didn't actually look alike because it's the internet and people will argue about anything some people were like you guys look absolutely nothing alike I don't get why this is even a story and other people were like okay that's the same person posted twice it was like yeah me and Laurel but four faces even Amanda's family was divided my mom did think we looked at like my husband he said that he couldn't really see it but he kind of sucks with faces anyways so why do people see different things in the same two faces well the answer gives us a clue about what doppelgangers really are a strange side effect of how our brains process faces so what is a face well duh Joe it's the eyes and the mouth and the nose and the dimples and the cheeks the color of the eyebrows all of these features together create a picture that you present to the world your face but a picture of a face isn't really what your brain sees when you look at someone when we recognize anything we're comparing what we see with a stored mental picture that's encoded in our brain turns out special cells in our brains are active only when we look at faces and they're not active when we look at other things so what are these facial recognition neurons actually seeing this person in ariana grande's thank you next to video really looks like Lindsey Lohan but it isn't Lindsey Lohan sure her red hair and the Mean Girls outfit are part of why we're fooled but watch what happens when we overlay their faces the geometry of the face how the features are arranged with respect to one another is almost identical even if the specific features like the eyebrows and the tip of the nose are different the same thing is true for Amanda and Meredith do you really look at our mouth or our nose it might not look similar but they're in like the exact same place like if you trailer like borings across your face like my nose in my mouth and my eyes hit at the exact same places as hers in the areas of our brain that recognize faces we think certain neurons fire for eyes that are this far apart others for a mouth that's here or a nose that's this long this combination of nerves firing creates a map or a code called a facial schema to our brains a face isn't a picture it's a pattern and if one of those coded patterns shows up somewhere unexpected we can see a face even if it's not there it's an effect called pareidolia I'll take a look at this photo of George W Bush and Dick Cheney it's actually George W Bush and George W Bush did you notice recognize this guy maybe he seems a little familiar but you can't quite place it it's two people Harrison Ford and George Clooney when they're together our brains decode them as just one face and here are two photos of the same person give them a quick look okay now let's flip the image all of these are examples of how we get fooled because our brains usually don't pay attention to the details of faces we don't have cameras in our heads we're running pattern recognition software between our ears and I guess this means we need a firmware upgrade of course the more time we spend with people the better we can tell their face apart from others because our face software gets help from our long-term memory like we could all tell if the president was replaced by some body double named Dave or something right there very handsome man Thank You mr. president you come for the science but you stay for the very current pop culture references but if you don't know two people like Meredith and Amanda you're more likely to think that they look alike researchers at Cambridge University developed a face memory test that you can take for yourself as it turns out I am very good at remembering new faces and speaking of remembering faces did you notice that we just switched Amanda and Meredith's photos some people are just better at facial recognition than others and scientists don't really know why people who don't think Amanda and Meredith look alike are probably able to sense details in their face patterns that others but what if someone's life depended on your ability to recognize and tell faces apart would you trust yourself well that's exactly what dr. Tegan Lucas does she's a professional face identifier or more accurately a forensic anthropologist who specializes in facial anatomy if police need to identify someone from an image they turn to her for help to the naked eye these people may seem to look the same and then if you call someone like me and we would be able to tell slight differences between them because we're trying to look for very very miniscule things let's imagine a face as a Rubik's Cube it might seem like you can only get so many combinations of nose eye and mouth shapes before you get a duplicate that's something that my research concentrate on is talking about probabilities of facial characteristics and body characteristics you know the probability of finding two people with the same face or two people with the same body and we found that these probabilities are comparable with DNA and fingerprints so our face is just as unique as a fingerprint or as DNA we factor in just eight facial measurements the odds of two people having the same face are about one in a trillion so basically impossible if I look at a nose I see maybe wide or skinny or how much it sticks up dr. Lucas sees nose width bridge with tip size tip shape tip angle the angle in relation to the chin the forehead how much the nose protrudes she knows her stuff even if you take something as simple as the ear the ear is unique between each and every individual and there's enough anatomical characteristics on the ear that we can actually identify someone from here and I've had cases of that so someone has has robbed a baby with like a balaclava that was on completely the wrong way and his ear was showing then we match them up and you know I asked her about the David Schwimmer look-alike thief yeah I picked quite a few differences mostly in the nose and he had a very square chin the day we look alike and then I look they're sure like oh yeah I could put this to rest in five minutes so I asked her to compare Amanda and Meredith here is what she found sorry Amanda had a triangular eyebrow shape meaning she had a bit of an arch in the my superior corner of the eyebrows whereas Meredith had a straight eyebrow amanda had an oval face shape whereas Meredith had a more elliptical face shape amanda had a v-shaped upper lip but in Meredith she has what we call a Cupid's bow meaning they project upwards but they're more rounded and Amanda had a rounded bottom lip whereas Meredith had a w-shaped bottom lip so it kind of had those points on the bottom in Amanda she had what we call a nasolabial is it's these folds here and she's got them quite prominently even when she doesn't smile whereas Meredith doesn't have those folds at all I'm like Amanda doppelgangers are never identical matches but they don't have to be to cause problems dr. Lucas is working on a case right now involving someone who's been in prison for over a decade maybe my mistake because their face might look enough like someone else's facial recognition is very unreliable in that moment when you actually calling upon someone to recall their memory entirely unreliable so if we get fooled so often maybe computers could do better than humans but I don't know computers can see a face in someone's knee or there was the time that an automated surveillance system in China publicly shamed a woman for jaywalking after seeing her face on the side of a bus but what if we let computers teach themselves how to recognize faces maybe they could get fooled less than we do why don't you try to find the matching photo a computer can do this almost instantly a company called thorn developed this software to help find missing kids we can able to help five about thorn fed images into a machine intelligence and let it learn over time until it was able to identify where a face is pick out its important features and match similar faces together what I find most interesting is that they didn't train it to see faces like we do it's evolved its own way of recognizing faces just like our own brains evolved neural networks that help us recognize each other but where computers are machine intelligence really makes the difference is it will memorizing such a large number of levels people I think a human being can remember most it's a thousand faces or in computer it's pretty straightforward the help of machine intelligence - you can memorize a million people or several million people the AI isn't perfect but neither are our own abilities but our powers combined can have serious potential if we think of a face like a lost needle AI makes the haystack way smaller from the get-go you know I think it's really where we are mostly going to work like five-minute face is where is this one with Eclair first and enable us to do things were enabled before this it's so science tells us that technically doppelgangers don't exist every face that's ever been is unique yours mine even between identical twins but science has also shown us that we're really good at fooling ourselves even when something is right in front of our face stay curious I want to say a big thank you to brilliant org for supporting PBS Digital Studios and our show is it me or is it some evil look-alike I'll never tell but I do know it would be so much easier to learn all the things if I had a doppelganger to running around but then I'd have to figure out how we could all share a brain and all that but a much easier way to sharpen your scientific skills and have fun doing it is to check out brilliant org brilliant is about learning through actual problem solving not just watching stuff they have sequences focused on that machine learning and neural networks which are exactly what people like Rubin and his team used to train their computers to do with the universe's most complex computers our brains already do so well to solve problems like this and ones we haven't even thought of yet you need a framework for thinking about and solving them brilliance is a place that you can do that brilliant math and science done right proud to support it's ok to be smart to learn more about brilliant you can go to brilliant org slash be smart