All around the world, people are experiencing the same terrifying vision in their sleep. I’m Corinne Purtill. This is Quartz. Subscribe to our channel for more videos. The vision is virtually the same everywhere. I collected accounts from forums, chat rooms, books, and interviews, and noticed a few common themes. He is dark. He is featureless. He wears a hat. And when people see him, they feel paralyzed, unable to speak. A crushing sense of breathlessness, like something evil is pressing on their chests. And when they’re finally able to move, he’s gone. – I haven’t seen him in years. But I fear him. Yeah, I do, for sure. I wanted to speak to someone who could make sense of all of this. – I think it’s a real challenge for scientific explanations to explain why some of these themes seem to crop up time and time again. Chris is a psychologist who studies paranormal experiences. He says people who see things like the Hat Man aren’t crazy or lying. That fear, and that vision, is real. But the explanation has a lot more to do with culture than ghosts. – If you look at the way it’s interpreted across different cultures, that’s absolutely fascinating, because you’ve got the same core experience, but it’s kind of got this cultural overlay. This nightmarish figure has inspired art and myths across cultures and history. In Assyria and Babylon, an evil spirit was said to leap upon unsuspecting victims as they slept. In ancient Greece, a doctor wrote of a demon that visited his patients at night, and pressed upon their chests. Similar specters appear in folk tales told from the Arctic, to Japan, to Newfoundland. And for most of history, no one knew why. By the late 20th century, the science of sleep evolved to offer another explanation: It’s called sleep paralysis. – You’re stuck in a state where you’re awake, but the only thing you can do is move your eyes, breathe… Alon Avidan is the director of the Sleep Disorder Center at UCLA. He says we’re always paralyzed while we dream — that’s normal. But when the brain wakes up before the body does, that’s sleep paralysis. – You cannot scream. You cannot talk. In fact, a lot of people experience sleep paralysis. And it can come with terrifying visions. Sleep scientists have a specific term for this: – One unique parasomnia is called “terrifying hypnogagic hallucinations.” And what happens is, the patient wakes up and they start seeing images of other people who are trying to hurt them. But even Avidan says he doesn’t understand why all those hallucinations are so similar. – It’s fascinating, in that you take individuals across different geographic entities, and yet the dreams seem to be similar. Why does it happen? Why are the dreams not pleasant? Chris, the psychologist, thinks he might have an idea. Sleep paralysis visions are shaped by cultural influences the dreamer may not even be consciously aware of. For example, that man in the hat looks an awful lot like a figure we’ve come to associate with horror. – Who the hell is that? – The Hat Man, when I sat and thought about it, the thing that came to my mind was, Freddy Krueger, and the Nightmare on Elm Street films, were actually directly inspired by sleep paralysis. This notion that you can be attacked when you’re asleep; that’s when you’re vulnerable. And of course, Krueger wears a hat. There’s still no definitive answer for why some people see these shadowy visitors. But those who do don’t have to be haunted by them forever. – Treatment for this is to have the patient to relive and re-experience the hallucination during wakefulness, during the day, and begin to imagine positive emotions, or associate positive emotions with that image. In truth, there is no stranger lurking in the corners of our rooms at night. The Hat Man is only in our minds, and that may be even scarier. So, have you seen the hat man? Definitely tell us about it in the comments. And subscribe to our channel for more videos like this one.