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Did you know we have a whole channel dedicated to the human mind, people and interactions between people? It’s called SciShow Psych! And here is a compilation of five videos from that channel explaining some common experiences you may have wondered about before.

Hosted by: Hank Green

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[Hank]: If you're watching this, you are probably a human, and we have a show that is all about you. It's called SciShow Psych, and there we talk about the human mind and people and interactions between people, and on that channel, we've explained common human experiences like riding a bike or forgetting what you were doing when you walked through the door, which might seem like simple things, but our brains always find a way to spice things up. So today we thought we'd share with you some of the weird, fascinating reasons behind simple things that a lot of us experience, and if you like it you can check out for more. We're going to kick things off with doorways. Have you ever walked into a room and forgot why you walked into that room. This is not just you, and you can blame your brain. Here is Brit one of our show hosts on SciShow Psych with more about that.
[Transition; "Do Doorways Actually Make us Forget Things?"] [Brit]: Does this sound familiar: You get up to grab your phone, or a cup of tea, or something else in the other room but once your there you have absolutely no idea why. Were you distracted? Sure, maybe, but it could also be because you walked through a doorway. Yep, according to Psychologists at the University of Notre Dame, something as simple as walking through a doorway can make you forget things. They found this out by testing undergrads in the lab. They asked students to place six blocks of various shapes and colors in a shoebox, cover it with a lid, and carry the box across one big room or into another room. There, the students were quizzed on the contents of their boxes. Had they carried a yellow sphere? What about a green cube? Most people could remember the objects most of the time, but when participants had walked through doorways, their performance was consistently worse. Something about doorways seemed to make them forget. This happens with not only real doors but in virtual enviroments, too, and even when people are asked to simply imagine crossing a threshold. It's called the location updating effect, or more simply the doorway effect. (2:01)

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You might think this is just a case of context like if you walk back into the original room maybe that can help you remember, but The Notre Dame Scientists tested this and that didn't make participants any less forgetful.

The forgetting wasn't just about being in a different room, the act of walking through the doorway was the culprit. So what's going on?

The best explanation has to do with how our brains process events. After all, you can only think about so many things at once. Working memory, our neural representation of what's currently happening is limited.

So the best way for our brains to deal with everything is to break it into chunks. According to this theory, known as the event segmentation theory, our brains create representations of events called event models which let us predict what might come next at any given moment like if you see someone tie one shoe, it's a pretty safe bet that the next thing they're going to do is tie the other one. But these event models need to be updated as the circumstances around you change.

Once someone's done tying their shoes, for example, having that model in your head isn't very useful. And that's where doorways, and other so-called event boundaries, come in. Doorways are a sign that something's changed and maybe you need to refresh.

The problem is that when your brain updates the status report, that old information isn't as accessible, even if you still need it. Psychologists also think people might have a hard time remembering things like those colored blocks in the experiments because they create two event models with those objects, one for each room. So, when it comes time to retrieve the information about what's in the box, or what you went into the other room to find, the two models compete and interfere with each other.

But, this whole system that your brain has for processing things still is useful, even if it sometimes leaves you in the kitchen wondering why you're there. That's because more often than not, passing through a door does mean that a new event is beginning, which means that it's okay to dump all of the information about the old event. So, this kind of event might be annoying but isn't really a bad thing, and it's not a sign that you're getting old or developing dementia.

Scientists actually checked this, and the doorway effect was just as strong in college students as it was in a group of older people. In fact, event boundaries like doorways sometimes might even help you remember. In a different experiment, the same Notre Dame psychologists challenged students to remember a list of words that was read aloud, half in one spot and the other half in another room or the same distance away within the same room.

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The test subjects remembered more of the words when they crossed through a doorway than when they just moved to another part of the room. Here, the doorway was beneficial. By divvying up the words in two separate event models, the brain can structure the information better and take more of it in. So, if you end up in your kitchen baffled by why you're there, don't worry, your brain made a tiny mistake. In the grand scheme of things, it's doing things just right. 
Hank: So physical doorways give an instant refresh to your brain and you forget what you were going to do in the first place. But what if it's not a real memory, but a dream? Why is it so hard to remember those? Like, we just wake up and poof, it's gone! That said, this also might just be me. You might be better at remembering dreams, or worse than me. Why is this? Well, let me explain.
Hank: It seems like some people can regale you with every last detail of the dream they had last night, while others can't remember whether or not they even had a dream. No matter which camp you fall in, everybody does have dreams, it's just that some people are better at remembering them than others. And whether or not you remember those surreal, unconscious experiences has a lot to do with the activity in your brain and with how well you sleep. Scientists still aren't totally clear on why we dream in the first place, but they have a decent idea of what our brains are up to when we do. We dream the most when we're in a state of sleep called REM. REM stands for rapid eye movement, and it's a stage of deep sleep that gets its name from the way our eyes move back and forth while we're in it. We typically have a few REM through the night, beginning around 90 minutes after we fall asleep, and each cycle can last between a minute and an hour. Even though you're sleeping deeply during your REM cycles, your brain actually acts a lot like it does when you're awake. For instance, when you're awake there is a lot of blood flowing to the cerebral cortex, the thin layer that surrounds the largest part of your brain, which plays a role in decisions and thinking creatively. (6:08)

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