Hi there, Shankar here. This week we are bringing you an episode from the archives.

Maybe more than any other hidden brain episode, this one brings a smile to our faces.

And right now, that's something we can all use. Here it is.

This is Hidden Brain, I'm Shankar Vedantu. When Sophie Scott was about six, she came across

her parents doing something very strange. They were rolling around, laughing.

In my memory, they were actually on the floor of the living room.

Absolutely overcome with laughter.

They'd laughed so much, they could literally do nothing else but laugh.

What had gotten laughing was a song. A comedy song about what people were not supposed to do

in toilets on trains. It's said to be quite a famous piece of music and it's going to go

customers will please refrain from passing more to while the train.

We encourage constipation while the train is in the station.

And as they remembered more and more of it, they got more and more helpless.

If you wish to pass the water, finally call a pulpit mug or place of S.O.N.

In the best way. Now maybe you're thinking, wait, this song isn't that funny.

But we've all been there, right? You're with a friend, they say something ridiculous.

And then your laughter triggers their laughter.

Sophie didn't know then that laughter would play a big role in her life.

But today she thinks about laughter a lot. She's a neuroscientist who studies the science of laughter.

So she often thinks back to that moment with her parents back when she was six.

Years and years later my father was mortally ill. I mean he thought he was dying, we all thought he was dying.

And the doctors didn't know what to do and it was all we were just sitting around waiting for something to happen.

...