This is Hidden Brain, I'm Shankar Vedanta.

Back in 2011, a 13-year-old girl posted a music video on YouTube.

It sat there for about a month without getting much notice.

But then, something totally unexpected happened.

The girl's name was Rebecca Black, and the song she was singing in the video was called Friday.

The song went viral.

Friday became the most watched YouTube video of 2011, with 167 million views.

The most watched YouTube video of 2011, with 167 million views.

Plenty of people watched the video to make fun of it, perhaps not knowing or caring that Rebecca Black was only 13 years old.

But a decade later, she's gotten the last laugh with the new remix of the song.

That version, it's also gone viral, with millions of views in the first few days after it's released.

This week on Hidden Brain, what makes certain songs, memes, and even social movements go viral?

We look at why they spread and how social contagion can be harnessed to build a better world.

How is it some social movements take off and spread, while others find themselves stuck?

Why do some companies soar and become household names, while others flame out?

Can you predict success and failure? Or is it all a matter of luck?

These are questions that have long fascinated Damon Centola, a sociologist at the University of Pennsylvania, and the author of the book Change.

Damon Centola, welcome to Hidden Brain.

Thank you for having me.

I want to start with one model of how something can spread very, very rapidly.

In late 2019, Damon, a few people got infected with the COVID-19 virus in Wuhan, the Chinese city.

Paying to picture for me of how a virus can go from infecting a small number of people in one Chinese city to a global pandemic.

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