Why do we dream?

0:00 Welcome to Philosophy is not boring by Kidopoly.com. I'm Mira. And I'm Finn! If you haven't already, tap follow wherever you're listening so you never miss an episode.

0:11 Hey Mira, have you ever woken up completely confused because you were just flying on a giant purple turtle wearing a cowboy hat, and then suddenly you're just in your bed?

0:22 Oh, absolutely. Or you're eating a huge donut that somehow tastes like nothing, trying to run away from a slow-motion marshmallow. And then you wake up and it's all gone.

0:34 It is so weird. It feels completely 100% real while it's happening. But the very second you open your eyes, you realise none of it actually made any sense at all. Today we are asking a huge question.

0:47 Why do we dream? What is actually happening in our heads when we go to sleep? And why do our brains make up these crazy movies?

0:54 It really is strange when you think about it. Every single night, you just close your eyes, lie perfectly still in a dark room, and your brain decides to build an entire invisible world for you to walk around in.

1:07 It really is bizarre. For a long time, nobody knew what was happening in there. Most people thought our brains just shut off when we sleep, like a car parked in a garage with the engine completely powered down.

1:20 That makes sense to me. You're resting, your body is resting, so your brain should be taking a nap too, right?

1:26 That's exactly what scientists thought for centuries. But everything changed in 1951, all because a student in Chicago named Eugene Azarinski wanted to look closer.

1:37 So what did Eugene do? Did he stay awake and just watch people sleep? Because that sounds really boring and kind of creepy.

1:46 He did actually, and he used his own eight-year-old son, Armand, for his experiment. Before Armand went to bed, Eugene gently taped these little sensors near his eyes.

1:58 Wait, he put wires on his kid's face while he slept. Was that safe? Did it hurt?

2:05 Totally safe. It didn't hurt at all. They were just sticky pads connected to a machine to measure the electrical changes of his eyes moving back and forth. Eugene thought the machine would just draw a flat, boring line all night because Armand was fast asleep. But I'm guessing it didn't draw a flat line.

2:23 Nope. Right in the middle of the night, the machine went absolutely crazy. The pens tracking Armand's eyes started swinging wildly back and forth on the paper.

2:33 Like he was awake and looking around the room at things.

2:36 Yes. Eugene actually went in and woke Armand up, thinking the boy was awake and just lying there in the dark. But Armand rubbed his eyes and said, I was just dreaming.

2:48 Whoa! So his actual physical eyes were darting around inside the dream. Looking at dream stuff.

2:55 Exactly. Eugene, along with a scientist named Nathaniel Kleitman, called this rapid eye movement, or REM sleep for short. They discovered that if you wake someone up during REM sleep, they almost always remember a vivid dream.

3:11 Rapid eye movement. That is such a perfect name for it. So we know when we dream, but why do we do it? What is it actually for?

3:22 Well, that's the big mystery. Scientists and philosophers have been chewing on this for a long time, and they still don't totally agree. One big theory is that dreams are for sorting our memories.

3:35 Sorting memories? Like a giant filing cabinet inside my head.

3:40 Kind of. Think about everything you did today. You learned new things in school, you talked to friends, you saw a weird bug on the sidewalk. Your brain has to decide: what do I keep forever and what do I throw away?

3:54 Oh, so the brain is like, keep the math lesson, that's important, but delete the memory of the weird bug.

4:01 Exactly. Some people think dreaming is just your brain doing that hard filing work while you're asleep. As the memories get sorted into folders, bits and pieces flash across your mind.

4:13 That completely explains why my dreams are always a crazy mix of what I actually did that day, plus random stuff.

4:20 Yep, but there's another really interesting theory. Some scientists think we dream to safely rehearse for danger. Rehearse for danger? You mean like a school fire drill? Exactly like a fire drill. It's called threat simulation. The idea is that a long time ago, early humans had to worry about being chased by wolves or bears.

4:43 Dreams gave them a safe sandbox to practice running away.

4:47 That actually makes sense. If the dream bear catches you, you just wake up. You don't actually get hurt. But your brain learns how to dodge and escape better for real life.

4:58 Yes, so even nightmares, which are completely ordinary and harmless, might just be your brain running its safety drills to keep you sharp and prepared.

5:07 Okay, the fire drill idea is really cool. But here's the problem I have with it. What about dreams that are just total, complete nonsense? You can't practice for a flying purple turtle attack.

5:21 That is a great point. And it brings us to a third major theory. The brain making stories out of random noise.

5:30 Random noise? What does that mean? Does my brain have radio static in it?

5:35 Kind of. When you sleep, the lower part of your brain sometimes fires off random electrical signals. Just total static, with no real meaning or plan at all.

5:47 Okay, but dreams don't feel like static. They feel like a whole movie that I'm inside of.

5:53 Right. And that's because the thinking part of your brain, the storyteller part up front, hates random noise. It desperately wants things to make sense. So it frantically stitches those random signals together into a story as it happens.

6:10 Oh, I get it. So if a random electrical signal hits my memory of a turtle, and another random signal hits my memory of flying, boom, flying turtle.

6:21 Exactly! It's called the activation synthesis theory. The signals activate, and your brain synthesizes them, it glues them together, into a narrative.

6:33 Wait, huh. If that's true, it means dreams don't actually mean anything deep or mysterious at all. It's just my brain trying to make sense of meaningless static. I don't know how I feel about that. It kind of ruins the magic.

6:48 It is a weird thought, isn't it? But you know, nobody actually knows which theory is perfectly right. And honestly, I think it's still incredibly magical that your brain is such a brilliant storyteller that it can take total nonsense and instantly direct a whole movie for you.

7:08 That is kind of amazing, actually. With a star, the director, the special effects team, and the audience, all at the exact same time.

7:17 So next time you wake up from a completely bizarre dream, or even a tricky, confusing one, here's a thought that might change how you see it. What's that? Instead of just being confused, you can take a second and think, wow, my mind is working really hard for me right now. Whether it's sorting out yesterday's memories so you can learn, giving you a safe practice run for tricky situations, or just painting a ridiculous masterpiece out of random noise.

7:47 I really like that. It makes me feel like my brain never really leaves me alone or abandons me. Even when I'm resting. It's always active, trying to help me make sense of the world.

7:57 Exactly! It's your brain looking out for you, keeping the lights on while you sleep. And here is a fun fact. Humans have been wondering and arguing about what dreams mean for thousands of years. But the craziest part of all, everyone dreams, every single night. But most of it is completely forgotten by breakfast.

8:19 Haha, that is so entirely true. I'll wake up thinking, I have to remember this, it was the best story ever. And by the time I'm pouring my milk into my cereal, poof, it's completely gone.

8:32 It's like a secret message that dissolves in the sunlight, which makes it even more of a treasure when you do actually manage to remember one. Right, Finn, quiz time! Okay, I'm ready. First question. What year did Eugene Azarinsky tape sensors to his son's eyes? Next one, what was the name of his eight-year-old son?

9:01 Question three. What do we call the stage of sleep where your eyes dart around? Here's number four. Name one of the three theories we talked about for why we dream. Last question. When do we usually forget most of our dreams? Great job! Let's see how you did. The first answer is, it happened in 1951.

9:33 For question two, his son's name was Armond. The answer for question three is it's called REM sleep or rapid eye movement. Number four, the theories are sorting memories, practising for danger, or making stories out of noise. And the final answer, we usually forget them by breakfast.

9:56 You know, I'm definitely going to pay more attention to my dreams tonight, even if they just disappear by the time I eat my toast.

10:04 Me too. I hope I get a really good, weird one tonight to puzzle over tomorrow.

10:10 If this episode made you think differently about your dreams, please leave us a five-star review. Just scroll down and tap the stars.

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10:40 See you next time on Philosophy is not boring. Bye.