Oh hi there, I wasn’t expecting you.
I just had the craziest dream, I wonder if it means anything?
[Intro Music]
There are hundreds of books, videos, and astrologers willing to help you decipher your dreams.
But despite what pop culture may have led you to believe, your dreams are no great mystery.
But you may have also been taught that your dreams have no meaning at all – that they’re
just random neuron firings in your brain turned into a story.
Truth is, we’ve known the purpose of our dreams for a very long time.
The human sleep cycle lasts around 90 minutes.
For the average person, that’s about 4 or 5 cycles per night.
There are also 4 or 5 stages per cycle depending on how you count – one of them happens twice.
But they always end with REM sleeping and dreaming.
Every mammal that’s been tested has been shown to go through a similar cycle and has
been observed dreaming.
So there must be some sort of evolutionary purpose.
In case you were curious, cats and ferrets have a cycle that lasts around 20 minutes.
There are two types of dreams, those that occur during REM sleep, or Rapid Eye Movement
sleep, and those that occur during non-REM sleep.
During REM sleep your eyes will dart around inside their sockets even though they are
closed so it’s easily detected.
When people are woken up during this stage they almost universally report that they were
dreaming.
During non-REM sleep your eyes don’t do that so dreaming can only be detected through
some sort of brain imaging like Electroencephalography – or EEG.
If I hadn’t been working in a lab for the last few years, there’s no way I would have
been able to say that.
When woken up from a non-REM dream, people will either report that they were dreaming
or just “thinking.”
This is despite the fact that during non-REM stages you’re in a deeper sleep so actively
thinking is pretty unlikely.
The reason it might feel like you’re thinking instead of dreaming is because non-REM dreams
are pretty boring.
This is the memory portion of sleep.
Your brain is going over things that you did that day, storing and discarding memories,
and the most important things you learned might be repeated over and over in your head
until they’ve been committed to memory.
Just cram for a test?
This is when you’re going to want to have a textbook under your pillow in order to learn
by osmosis.
Just start a new data entry job?
This is when you’re going to dream about Excel.
Or making sandwiches.
Or counting money.
Or whatever it is that your brain knows will be important for the future.
So if you’re woken up while you’re just rehearsing your new job or replaying the latest
episode of Game of Thrones in your head, you might mistakenly report that you were just
thinking.
Even though the people who were watching you definitely know that you were asleep.
This is why sleep is so important for your memory and why sleep deprivation can cause
some serious memory issues.
Think of your brain like a computer.
During the day you’re storing memories in your RAM or short-term and you can only transfer
memories from your RAM to your hard drive, long term, during sleep by dreaming.
If you don’t sleep, your RAM gets overloaded and, assuming you don’t crash like my piece
of- you’ll start losing entire memories or not be able to focus anymore.
Okay this is boring, get to the fun stuff.
Where’s the dreams about talking bananas?
[Thump, thump, thump]
Well I hate to break it to you, but those
are just more pop culture myths.
Your brain is creative but it’s not that creative, it can’t just make up someone
out of nowhere.
Every person that you’ve seen in your dream is someone that you’ve seen before – either
in real life or in por- on TV… yeah, TV.
Your brain is only capable of dreaming about things that it’s experienced or seen.
You’ve never dreamt about a talking banana.
Because your brain knows that’s impossible.
If you honestly think that you’ve had a crazy dream like this, you’re most likely
committing the memory error of misattribution.
You’ve seen it in a cartoon or a movie or something and you’ve mistakenly taken that
memory as one of your own – everyone commits memory errors, and this is by far the biggest.
It’s probably a video topic in itself.
But if you still think that you’ve had these crazy dreams, stick around to the end because
I have an assignment for you.
So you told us about boring dreaming and just ruined my childhood.
What is REM sleep then?
I’m glad you asked banana with a weirdly similar voice to mine.
REM sleep is the learning stage of dreaming.
Your brain goes into simulation mode and plays out possible future scenarios, no matter how
bizarre or unlikely they might seem.
Like talking bananas?
No not like talking bananas!
Well why am I even in the script then…
Since other mammals have REM dreaming, we can assume that they are dreaming about something
realistic.
Just like we do.
These simulations are when you dream about dating a supermodel, or being naked in front
of a class, or some other outlandish – but possible – scenario.
Why would your brain dream about such weird things?
To prepare you for the future, in case they actually happen.
This is also when you have nightmares.
[Distorted screeching]
What’s the purpose of nightmares?
Well it’s just another possible future scenario that your brain puts you through in order
to prepare you for the future just… scary.
Everyone gets them, but having them too often could be a sign of PTSD or depression.
But they do serve some sort of evolutionary purpose as well.
Ever see your dog or cat… or ferret… just jump up and run around after it was asleep
for a while?
It probably just woke up from a nightmare.
Naked while giving a presentation to the class?
Don’t worry, it happens to all of us, and when it happens to you, you’ll be ready.
Being chased by a ninja?
Well you’ll probably die but just in case you might be able to get away.
Ooh or pirates!
Ooh, ooh or pirate ninjas… pirinjas… no that doesn’t work.
Pir… piranjas?
Pir… piranhas?
Piranhas!
Because of how important REM and non-REM dreaming is for learning and memory, you can actually
use that information to your advantage.
The best time to study for an exam is weeks beforehand.
The second best time is right before you fall asleep.
In the very unlikely event that you have to study right before the exam, take a 90 minute
nap between studying and taking the test.
You will do measurably better on the exam than those who decided to cram for those full
90 minutes.
Since you’re not going to run your own randomized controlled experiment to confirm that, you’re
just going to have to take my word for it.
Dreaming is also when your brain will defragment your hard drive and pull information from
the long term that it thinks you might need for the next day by putting it into the short
term.
Hey didn’t you say something about an assignment earlier?
Go away.
I just wanted to make sure I didn’t miss out on any homework.
[Trash can closing]
This assignment is for everyone.
To test out how your brain can do deep searches while you’re asleep, the next time you have
one of those tip-of-the-tongue moments – Who was the actor in that one movie?
I can see his face, it was in a city or something?
Ugh I don’t want to cheat by using IMDB.
It doesn’t matter what time of day this happens.
Write it down and put it next to your bed.
When you wake up, the first thing you should do is read your question.
And ding, it should come to mind.
Now to my banana dreamers… or anyone else who is curious for that matter.
Keep a dream log.
I know, I know it sounds stupid, I was hesitant to do it myself, but give it a try for a few
days.
As soon as you wake up, write down exactly what you were dreaming about.
It has to be fast, because memories for dreams decay incredibly fast.
Your brain knows they weren't real, so it doesn’t commit them to memory.
Within 5 or 10 minutes of waking up the memory is going to be completely gone.
You can actually run this test yourself too.
Wake up, think about what you were dreaming about, do your morning routine and then try
to think of what your dream was again.
You probably won’t be able to come up with anything unless you’ve been thinking about
it the entire time.
Despite not finding any bananas in your dreams, you might also find that your dreams are actually
pretty short.
Most REM dreams last about 5 to 20 minutes.
Despite what Inception might tell you time dilation is not a thing.
When woken up people can pretty accurately tell how long they’ve been asleep.
So the next time you see a dream about a talking slice of pizza on TV or your friend tells
you that obsessively dreaming about cigars must mean that you’re secretly obsessed
with… cigars.
You know they’re being ridiculous, because now you know better.
[Outro music]