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We are constantly recognizing faces countless times a day, but how do our brains distinguish those faces so easily?

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Thatcher Illusion:



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We are constantly recognizing faces countless times a day, and most of us take it for granted. Of course your best friend looks different from your mom, who looks different from Beyoncé.

But if you think about it, every face is pretty similar. Most of them have two eyes, a nose, and a mouth, and only vary just a little bit in shape, and color. So, really, distinguishing faces in a crowd should be as difficult as distinguishing birds in a flock or bricks in a wall.

Luckily, you know because otherwise we'd be terrible at all interactions, humans are exceptional at perceiving faces. Part of the reason for this is a specialized brain region called the fusiform face area, or FFA. The FFA is tiny and located in the brain's temporal cortex, which is generally responsible for object recognition.

Since faces are special, they get their own private real estate there. We think that the FFA is face-specific because we can observe how the brain responds to faces compared to other objects. In fMRI experiments, which measure brain activity during specific tasks, the FFA is active when looking at faces — whether they're real people, photographs, or even drawings.

But other objects, like a cup of coffee or a building, activate other parts of the temporal cortex. Not the FFA. However, scientists are still debating if the FFA is actually specific to faces, or if it's just really good at identifying complex objects we see a lot.

Some researchers argue that if someone saw more birds than human faces, for example, their FFA might specialize for birds. And they might be better at picking out a bird from a flock than a face from a crowd. But we're still looking into these questions.

So how does this brain region help you process the world around you? Essentially, we see most objects as a collection of features. Like, we'll see something with a screen, buttons, and ports, then put all that information together to recognize it as a cell phone.

But we process faces more holistically. We know how facial features are usually arranged in relation to one another, and can see them all at once as part of a face. In fact, we might be a little too good at recognizing faces, which leads to a phenomenon called pareidolia.

You might have seen pictures of faucets, or rocks, or even toast where you can't help but see a goofy little face in there, even though you know that it isn't intentionally there. The layout of features is really important because the FFA only responds to faces in their normal arrangement and orientation. When one is upside down, you might know it's a face, but your brain doesn't treat it like one.

Take the Thatcher Illusion, named after Margaret Thatcher, whose face was originally used to demonstrate this phenomenon. If you take a picture of someone's face and flip everything upside down except for the eyes and mouth, it doesn't look that different from a normal upside-down face. That's because your brain's not viewing it as a face.

It's just a collection of features, and every feature on its own looks pretty normal. But if you flip that image over, so the eyes and mouth are upside-down while the rest of the face is upright, it becomes terrifying. Your brain recognizes it as a face, and realizes that something is very wrong overall.

For some of you, though, face identification might actually not be any easier than telling birds apart. Or you might not see random faces on inanimate objects. Estimates have found that about 1-2.5% of the world's population have a condition called prosopagnosia, or face blindness.

To them, faces aren't special and are processed like any other object. This can be the result of a brain injury like a traumatic head injury or stroke that affects the FFA. Others have congenital prosopagnosia.

As babies, they don't develop normal face recognition abilities. Based on current research, this condition is likely hereditary and also involves the FFA, but scientists are still looking into that. Fortunately, most people with prosopagnosia can still recognize their friends and family.

They just have to work harder at it. For instance, they often actively memorize distinct features about friends, like that Bonnie has long pink hair. So if Bonnie gets a haircut, they'll have trouble recognizing her.

Many of these people never even realize that they have prosopagnosia, or that they see faces differently from everyone else. They might just assume they're “bad at faces” and write it off. So human faces are an interesting paradox.

They're all quite similar, but subtle differences make them super unique, and our magnificent brains make them surprisingly easy to recognize. The most advanced computers still have difficulty recognizing faces, but our brains make this complicated thing seem very easy! Thanks, brain.

And thank you for watching this episode of SciShow Psych, with a special thanks going out to our patrons on Patreon, who make these videos possible. If you want to help support our team and free psychology education online, you can go to [ ♪ OUTRO ].