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Hey, smart people, Joe here.

What do you like to do for fun?

Me?

I enjoy a game of B-ball, and I especially like watching bee ball.

According to scientists, these bumblebees are playing.

In experimental settings, they'll roll objects around just for fun.

I mean, look at them, they're clearly having a ball.

Animals as simple as bees and as complex as you and me like to have fun.

But what's the point of fun?

Do all animals have fun?

And for that matter, what is fun?

(whimsical music) Fun starts with the letter F, but fun actually begins in your brain.

Almost every animal, from fruit flies all the way up to humans, have bodies that are wired to seek out rewards.

And in a brain, those rewards come in the form of chemicals that fire certain patterns of neurons and create the sensation of pleasure.

These reward systems evolved to encourage animals to repeat behaviors that are good for their survival.

You do something, get some survival points, get a reward, then do it again because it feels good.

So when a bumblebee lands on a flower and starts eating nectar, it activates its reward system.

Eating nectar is good for the bee, so it releases chemicals that create a sensation of pleasure, which makes the bee want to drink sweet flower juice again, and again, and again, kind of like me and queso.

(ethereal music) Humans have similar systems, they're just way more complex.

Our brains reward centers are connected together by a special pathway powered by a special feel-good neurotransmitter.

When this pathway activates, the neurotransmitter starts a chain reaction.

It stimulates the parts of our brains that make us want to do things and feel good for doing them.

When something feels good, what we really mean is that certain cells in certain parts of our brain are responding to specific chemicals released by other cells in our brain.

That's what fun is, floods of unique neurotransmitters.

And dopamine doesn't just make things feel good, it makes us want things too.

So when your brain gets that dopamine surge, it pushes you to get that thing that makes you feel good.

And then when we get what we want, it feels good, and we've got a nice little feedback loop.

This is how we learn what's fun so that we will repeat that behavior in the future.

Fun happens when the chemistry cocktail in a brain is mixed up just right, which is pretty much true for, like, all human feelings actually.

Pleasure is a way to influence how we and other animals behave.

Eating when we're hungry, sleeping when we're tired, socializing with others.

These are behaviors that help us survive, so they feel good.

And this evolutionary system works really well, so well that there's a lot of things, from drugs to social media, that hack these reward systems to make you repeat behaviors, even if what you're doing isn't actually fun.

But we can also hack these reward centers for good too.

And one way that humans and other animals do that is by playing.

Play, scientifically speaking, has to meet a few different criteria.

First, play is voluntary and spontaneous.

That means the animal isn't doing it in response to stress or something.

Play behaviors are also repeated over and over, but the key thing is that playing doesn't help the animal survive right now.

Instead, play is a way to practice the skills that the animal will need to survive in the future through behaviors that aren't directly tied to survival, the way say, eating or drinking are.

In the case of the bumblebees, scientists think playing with balls helps bees develop motor skills that they'll need later so they can find that sweet, sweet nectar they love so much, because flowers could be kind of tricky.

And that's the thing about play.

We do it because it's rewarding all by itself, not because we're getting an outside reward for that behavior.

Like, if bees got a sip of nectar every time they rolled a ball, they'd do it over and over again because they're getting food.

But the bees rolled balls because playing was pleasurable on its own.

Play rewards us with a mental dopamine hit, which makes us want to repeat that behavior again and again.

Repeat that behavior again and again.

Repeat that behavior again and again.

That's why kittens chase yarn to become better predators, and why apes play with sticks so they can learn to use tools.

Almost everywhere scientists have looked for play in the animal world, they've found it.

The fact that play happens to be fun gives animals incentive to practice behaviors and get good at them.

This is especially true for younger animals who've gotta prepare for surviving in a big, scary world.

Humans play to learn the skills that will need to survive, just like other animals do.

But humans are special, because honestly, we've taken play to a whole other level.

Beating a video game won't help you hunt your own food, but it might help you develop the mental skills you'll need to solve super complex problems.

Like, kids playing with blocks might seem simple, but they're actually doing some pretty intense brain development.

They're learning to classify things as they sort blocks into different sizes or colors.

They're observing the rules of physics and gravity.

They're developing problem-solving skills.

Scientists believe that play is part of why humans have been able to evolve from nomadic hunter gatherers into these technological apes with pants that we've become.

Play allowed our ancient ancestors to adapt to new environments and develop the skills to survive in them, like building new weapons or finding new food sources.

Play has helped our species survive so well that we now have free time.

Time that we can fill with fun, not because it's evolutionarily necessary or required for our direct survival, but just because it feels good.

Speaking of which, if you're looking for a good dopamine hit, now is the perfect time to like this video.

Your neurons will love it.

Anyway, leisure time has given humans the time and space to do amazingly creative things, like write novels, paint pictures, make science videos.

And humans freedom to have fun in a way that no other animal does has changed the world too.

Back in the 17th century, clockmakers started turning the wheels from clocks into these moving robots called automata.

They created all sorts of weird mechanical creatures, like a digesting duck that ate, it flapped its wings, and even pooped.

One of the most famous automata-makers was Jean-Joseph Merlin.

The owner of Merlin's Mechanical Museum, filled with his inventions, like self-propelling wheelchairs and roller skates.

But the most important machines in Merlin's Museum were these two dolls that could walk and dance all on their own.

They happened to capture the imagination of one young boy who visited the shop named Charles Babbage.

Those two dolls had no real purpose, except for pure fun, a laugh, a shot of dopamine, but they changed Babbage's life.

His fascination with these machines inspired him to design the difference engine with Ada Lovelace.

It inspired the world's first primitive computing machines.

And without the difference engine, we wouldn't have computers like the one that you're watching me on today.

That all happened because of the products of human fun.

It's fun to have fun, but having fun is also an important part of learning how to be a human in the world around us.

It's a way for other animals to learn how to survive in their worlds.

It helps us practice everything from our motor skills to interacting with others, and it inspires us to solve the world's big problems.

We're just never conscious that that's what we're doing when we play.

'Cause if we were, it wouldn't be very fun, would it?

Stay curious.

Hey, you made it to the end screen.

We got a new set, see you next time.