No, you haven't read this before (unless you're my editor), but I wouldn't blame you for feeling that way. Pretty much everyone gets that bizarre I-swear-I've-been-here-before feeling at some point. Déjà vu is still a pretty mysterious phenomenon, but researchers are putting the pieces together. And even though it can feel freaky, it turns out it might actually be a good thing. So what's actually happening when you get that weird feeling? There are a couple of different theories about the way déjà vu works, but most of them operate from the idea that it's a fairly benign — and possibly beneficial — memory issue. Essentially, it goes like this: You've seen something that was deemed inconsequential, such as a stranger's face on the subway, so you "forgot" it. Then, later, you might see someone else who looks very similar to that first person and you get a sense of eerie familiarity, but you're not really sure why because you don't readily remember the first guy. It's almost like your memory is too good, but the result is actually a false memory — you're confusing the second face for the first. Another theory, called "double perception," suggests that we're actually seeing the same thing twice, but we didn't really register it the first time. Maybe you walk into a new restaurant to meet some friends, but you glance down at your phone to check a text as soon as you get inside. So you did see the layout of the restaurant, but you were immediately distracted. Then, when you look up from your phone, you see it again but it feels like the first time — with a weird sense of having seen it before. But we know that you don't have to actually have experienced that initial thing firsthand to feel a that sense of familiarity when something uncannily reminds you of it later. For instance, people have traced their déjà vu back to places they only saw in TV shows or photos. So it's not totally surprising that more recent research — especially with the help of brain imaging and virtual reality techniques — reveals that the process is a whole lot more complicated than an overactive memory. For instance, in a 2012 study published in Consciousness and Cognition, researchers were able to induce a feeling of déjà vu (but not actual memories) in participants by having them walk through virtual 3D locations that shared specific structures. For instance, the windows in a virtual bedroom followed the same shapes as a set of wall shelves in a virtual closet. Another study, this one presented at the International Conference on Memory in 2016, found that feeling might actually be a signal that your brain's memory checking processes (not memory formation) are at work, explains New Scientist. Here, researchers read 21 participants a series of words that all related to but did not include the word "sleep" (e.g. night, pillow, dream, bed). Then, the researchers asked their participants if they'd heard a word beginning with the letter "s." They all answered correctly that they had not. However, when they were asked later whether or not they'd heard the word "sleep," the participants really freakin' felt like they had heard that word, thanks to all those other words. But they knew, because of the earlier question about the letter "s," that they hadn't. That contradiction turned out to be a perfect recipe for déjà vu. Participants' brain scans also confirmed that the parts of their brains that increased in activity when answering the question weren't areas we usually associate with memory formation (e.g. the hippocampus) but were, instead, prefrontal areas involved in making decisions. It's almost as if participants were on their way to creating a false memory of the word "sleep" but their déjà vu feeling told them something wasn't quite right. So, truthfully, we're still figuring out exactly what's going on when you get déjà vu. We can safely say it's not a glitch in the Matrix, and we can suppose that it's actually a sign of your mind's very complicated memory processes working as they should. With any luck, knowing that will help you shake that unsettling feeling next time it happens.