With 1 billion unique visitors per month, YouTube offers a glimpse of the online world's tastes and interests. And this year, one notable trend — for better or worse — is that people are spending more time watching videos about video games.

In October, Swedish gamer PewDiePie had the most subscribed-to channel on YouTube. PewDiePie, whose real name is Felix Arvid Ulf Kjellberg, records himself playing videos and commenting in English.

In this episode, PewDiePie is playing Walking Dead (and be advised that this video, like many others like it, contains profanity and violence):

PewDiePie, 24, has more than 18 million subscribers. That's more than pop stars Rihanna, with 11.8 million, and Eminem, with 9.5 million.

Kevin Allocca, head of culture and trends at YouTube, explains PewDiePie's appeal this way: "He is a guy who's basically your most fun friend to hang out and watch video games with."

Allocca points out that video games have become a big piece of pop culture. For example, Grand Theft Auto V grossed $1 billion in its first three days on the market this fall, making it the fastest-selling entertainment property of all time.

Yet video games don't get much love in traditional media, he says.

"Gaming culture and gaming events are very much a part of pop culture, but they aren't necessarily always thought of in the same way that we think about someone like Miley Cyrus."

Sam Barberie, an avid gamer and YouTube user, says he goes to the site "for the sake of nostalgia — to visit an old game that maybe I don't have anymore. But I'll think, you know, 'Wow! How awesome was that Zelda fire temple?' and I can cue it up and watch a few minutes of it."

The Rise Of Pop Science

In case this has you thinking, "Oh, great, another way that YouTube has given us to waste time (as if cat videos weren't enough)," here's the good news: The number of people watching educational videos on YouTube has surpassed cats.

Subscribers to educational channels have gone up threefold this year, and the most popular video was a clever online hearing test from AsapScience called "How Old Are Your Ears?"

It starts with a pitch everyone can hear, but as the video goes on, your ears show your age.

This kind of pop science is growing in popularity, says YouTube's Allocca. Many videos are produced by real scientists — Canadian biologists Mitchell Moffit and Gregory Brown made the AsapScience video. Many use animation.

"We've seen a lot of ... what we call 'explainer videos.' These are short videos that take a concept and break it down and explain it to you in simple terms," Allocca says.

Alas, with 1.8 million subscribers, AsapScience doesn't have nearly as many as Rihanna. But there is a lot more educational content coming online, including entire courses from major universities such as Stanford.

Phil Hill, an educational consultant with MindWires, says video is a medium that is setting science free from the limits of textbooks. "Video is very natural to ... actually show these scientific phenomena," particularly physics and chemistry-based disciplines, he says.

Hill adds that many people in the education field have been surprised at how popular educational videos are.

"I'm not aware of anybody who's predicted how big it would be," he says. "Maybe the fact that people would be interested, but not at all in how much interest would be drawn to this."

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