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At some point, we've all wondered why something as annoying as “Friday” or as delightful as Grumpy Cat can arrive so suddenly and overwhelmingly in our Internet lives. The Dress was everywhere for three days in 2015, before everyone got over it.

And who knows what picture or joke or video will dominate your news feed next? So why do things go viral? To be honest, this isn't something a lot of people have studied.

Really, the only thing newer than the Internet is taking the Internet seriously enough to publish a peer-reviewed study about it. But, when it comes down to it, sharing on the Internet is a lot like other kinds of social sharing. Gossip and urban legends spread like wildfire, too.

Both of these types of sharing have been shown to be driven by emotion. And if you think emotion isn't everywhere on the Internet, then this might be your first time on the Internet.... Welcome!

It was this line of thinking that led a group of researchers to look at almost 7,000 New. York Times articles from three months in 2008. They were trying to figure out what kinds of things got an article shared enough to make the Times' most-emailed list.

And emotion was the culprit, measured by both computer algorithms with databases of words and humans. Although the Internet can seem like a cesspool of negativity, the scientists actually found that articles that were emotionally positive were more likely to be shared than those that were emotionally negative. But an article that was very negative was more likely to be shared than one that was only mildly positive.

So it wasn't just whether the emotion was positive or negative that mattered. It was also how arousing that emotion was: if you got your lungs pumping and your heart racing a little bit. The same lead researcher did another study, too, where they specifically looked at arousal.

They had 93 students watch videos that provoked either contentment, amusement, sadness, or anxiety. Amusement and anxiety are both considered high-arousal emotions, while contentment and sadness are considered low-arousal. They found that watching one of the high-arousal videos made the viewer more likely to share a neutral article or video that they saw afterwards.

And in second experiment with 40 participants, the researchers found that even just making people run in place for a minute to increase arousal was enough to increase sharing. Which...what!? Wow.

This might be partially why over-the-top “clickbait” headlines work so well—they're trying to shock you or make you laugh. But there's more to social sharing than just arousal. The same researchers pointed to other factors that seem to make something shareable, including how interesting, useful, and surprising it is.

Like, y'know, ibexes licking salt off the side of a nearly-vertical cliff because they crave that mineral. And sometimes what goes viral has little to do with the content at all. Sometimes, it's all about us.

In the 1990s, a team of researchers proposed a new idea for why people go along with trends and fads. They called this concept an informational cascade, which is what happens when one person makes a decision and then others, rather than gathering information to make their own decision, base their decision on the first person's. It might seem like a silly thing to do.

But if you think that someone else's decision is based on factors that would guide your own, it can be easy to just agree with them, whether they're a friend or an expert. This hypothesis could help explain why you might think one kind of car is safer than another, why everyone is wearing crop tops this summer, or why books that hit the New. York Times bestseller list tend to stay there for a while.

And once momentum gets started, it keeps on going, thanks to the bandwagon effect: the more people adopt an idea or belief, the more likely others will too. Simply having the sense that many people support an opinion or think a video is funny can cause others to retweet again and again. But memes don't last forever.

And the idea of an informational cascade can also explain why fads die — why yesterday's covfefe joke is today's…like, whatever that is by the time this is uploaded. The premise of an informational cascade is that many people's decisions are based on the research and thoughts of a few, hopefully well-informed people. . But when a bandwagon grows, it doesn't increase the amount of knowledge that went into that first shareable thing.

Which means that receiving information that contradicts the idea — maybe a recall from that super safe car company or some evidence that a seemingly scientific fact was just a hyped-up rumor — can pretty easily dislodge it. Or when the novelty wears off, because even dramatic chipmunk isn't as hilarious when you've seen it 100 times, a meme might die a natural death. People are already jumping on the next bandwagon.

So, while there are many, many things on the Internet that remain mysterious, there is some sense to what goes viral. It's the stuff that makes us laugh, the stuff that makes us mad, and the stuff that people we trust tell us we should share. Which is why you should definitely share this video to everyone you know.

Thanks for watching this episode of SciShow Psych, which was brought to you by our patrons on Patreon. There;s bunch of you, and you're really great. If you'd like to be one of those people and help us making episodes like this, you can go to patreon.com/scishow.

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