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Mirrors can be pretty freaking creepy. Don't believe it?

Go into the bathroom, turn off the lights, and stare at yourself in the mirror. Give it a minute or two … and you'll start to see things. Strange things.

That's what puts Bloody Mary right up there with Seven Minutes in Heaven and Truth or Dare on the list of best old-school slumber party games. In the 80s movie version, you say Bloody Mary's name three times and summon a terrifying demoness in the mirror— which, I'm doing just fine without those particular nightmares, thank you very much. It's weird that looking at your reflection for too long makes you see a face in the mirror that's distorted and definitely not yours.

That's literally the opposite of what mirrors are for. But even though it's a little freaky, it can tell us a lot about how our brains process images, especially faces. In 2010, an Italian researcher asked fifty people to look into a mirror for ten minutes in a dimly lit room and write down everything they saw.

Two-thirds of them saw a distorted version of their own face. Over a quarter saw someone that they'd never met before, or what looked like an old woman or a child. And I'm literally getting goosebumps; this is freaking me out.

Almost half reported seeing quote-unquote “fantastical and monstrous beings.” Some of this weirdness can be explained by the Troxler effect— where things in your peripheral vision start to fade as you focus on something in the middle. That's because the neurons in your eyes, like other sensing neurons, stop reacting when they get the same stimulus over and over and over again. It's kind of like how you get used to smells, or stop feeling your shirt on your skin when you're sitting still or have no idea that these glasses are always on your face even though they're always there.

But you don't just see holes— your brain tries to fill in gaps in your visual field by blending with the surrounding scenery. So staring into your reflection's eyes can make your chin, ears, and forehead fade, Cheshire Cat-style. But the Troxler effect alone doesn't explain why you see other people in the mirror.

Psychologists think that may have more to do with the way we perceive faces. Studies like the Thatcher illusion, where researchers flipped the the eyes and mouth on a picture of Margaret Thatcher upside-down to create a horrifying monster, show that we process the image of a face as a gestalt: a whole that's greater than the sum of its parts. So when certain features that you know are supposed to be part of a face are wrong or disappear, you start to have trouble processing them.

Some researchers think that's what's happening when you stare in the mirror for too long. The Troxler effect causes distortion and fading, which disrupts the assembly of various facial features into a gestalt—therefore making the face feel more like it belongs to someone, or something, else. All 50 participants in the 2010 study reported feeling some amount of dissociation from their reflection.

The way they felt about the things they saw in the mirror depended on what they saw— those that saw a terrible monster were understandably more freaked out than those that saw a rando smiling at them. But they all had the sense that the face in the mirror belonged to an “other”— a sign that high-level facial processing was being disrupted. Not recognizing your reflection might not seem like that big of a deal, but there's a good reason it freaks people out: the ability to recognize yourself in a mirror is strongly linked to your development of a sense of self.

It's something few species can do, and even we humans can't do it until we're about 20 months old. Recognizing your own reflection isn't the only indicator of self-awareness, but it's a pretty important one. Researchers think it's part of a series of milestones that lead to developing your sense of self, as well as the understanding that other people have their own beliefs and desires.

So looking in the mirror and seeing a face that's not your own might be more than just creepy. It might actually cause a bit of an identity crisis for a second there. What psychologists can't explain is why we see monsters.

Weird, creepy, Bloody Marys? Sure. But these ideas don't fully explain why we see non-human faces.

It's one of those psychological mysteries that, when solved, could teach us a lot more about how our brains work. So if you're getting chills looking at your reflection, just turn on the lights and maybe don't look quite so long at yourself in the mirror. It's not actually a monster.

Pinky swear. Alright, SciShow Psych viewers, I got an EXCITING ANNOUNCEMENT for you! Some of the SciShow team and I were talking about a problem that we often have.

People will ask us, “what do you want for Christmas or your birthday?” and then we feel kind of bad for not having a good answer to that question. But then I was thinking, there are some things that I've gotten for myself or that I want or that people have gotten for me that I really love! Because it's symbolic of my love of the world, or lets me do experiments on myself or it lets me learn more about things!

So we have put together a collection of artifacts of this universe … we got a limited number of each of these things, and we have put them up at a store called SciShow Finds. These SciShow Finds are curated by me, they are things that I would love to get in my stocking. We're going to continue adding new finds as we find them throughout the year, and the new ones will replace these old ones, so all of these products are only around for a limited time.

You're bound to have friends or family who would love these Mars Socks, trilobite fossils, or this Space Shuttle lapel pin. And, if not, maybe you want to get them for yourself or just shoot that link over to anyone who asks you what you want for Christmas and say, “You know, anything from this site would be really cool. Mom was probably going to get you socks anyway, now she's gonna get you some socks you're really gonna like.

And know that when you buy from SciShowFinds.com, or you send that link to somebody, you're also supporting SciShow. So, thanks for doing that. And thanks for watching because that's another way to support us. [OUTRO ♪].