In the world of movie trailers -- a cottage industry of its own, one that can tell us more than we might want to know about how the human brain is stimulated, what tickles our collective Buy Buy Buy fancies -- one of the most successful, revolutionary trailers of all time was for the movie "Paranormal Activity."

You remember those movies, don't you? They used to come out every Halloween, until recently, when their box office momentum finally died out. You probably don't remember the plot of these movies -- there were these cursed sisters, or something -- or even any particular detail from any of them. (Though the third one is the best one.) When you close your eyes and think of the "Paranormal Activity" movies, I bet you don't think of a shot from the movie at all. I bet you think of watching the audience watching the movie. Those night-vision cameras capturing the viewers shrieking and gasping and clutching the person next to them. That is because of this trailer.

The genius of that trailer is that there is no way anything in the movie could possibly come up with that would be as exciting and terrifying as what you imagine those people are watching. What on earth could possibly be so scary that it would cause that reaction? I don't know, but come see "Paranormal Activity" and find out. People had to watch it to know. The reason we remember the video of people watching the movie more than the movie itself is because we're really watching ourselves. We've seen lots of scary movies. But seeing that was new. 

Sometimes, it's more fun to watch people watching something than it is to watch the thing they're watching.

On Sunday afternoon, the North Carolina Tar Heels beat the Kentucky Wildcats to advance to the Final Four in one of the most riveting basketball games of the season. The game was clinched with a last-second jumper by Luke Maye, just seven seconds after a crazy game-tying three by Kentucky's Malik Monk. It was a wild, lunatic finish that you can watch right here.

That's quite a sequence. But is it OK that I in fact find this reaction shot of Kentucky fans watching those final 10 seconds even more riveting?

Man, that clip has everything. Fear. Exhilaration. Jubilance. Pandemonium. And then … devastation. That might in fact be the range of human emotions in 30 seconds. That's what sports does to you. Put Falcons jerseys on those guys and slow the video down so it lasts four hours -- then you have a Super Bowl reaction video. That's life, right there.

The best part is that we know the story in a way that those watching don't. We were too busy watching the game to think about how others were watching the game, so we get a kick out of watching someone else, without our hard-earned knowledge, react to something spontaneously. We feel in on the joke in a way they are not: Oh, Kentucky fan, look how joyous you are … you have no idea what is coming. This power is artificial, of course, but it's still addictive: It's fun to watch someone else not know what's about to happen because when we were watching live, we were all that person. Lord help me if they ever put a camera on me during a Cardinals postseason game or an Illini tournament game. I lose all touch with rationality and the physical world during a sporting event I care about. The person you would be watching would be, probably the purest version of me, which means it's the last version of me I'd want you to see. We are never more ourselves than when we are acting on pure emotion, and nothing brings out pure emotion like sports.

That's why there are times that I think the fan reaction video is the Internet's lone salvation, the only thing that makes these hours we spend every day staring into the abyss to be worth it. 

As we head into the Final Four, with North Carolina and three teams that the rest of the country will be cheering to beat North Carolina, it's worth remembering that the Final Four, along with the World Series, the NBA Finals, various college football playoff and rivalry games and, especially, international soccer tournaments are the greatest generators of fan reaction videos you will find. (The Super Bowl, while usually dramatic, is not actually great for these videos. Too many people at the party who don't care about the game. Fan reaction videos are for the diehards only.) Last year's National Championship Game gave us The Shot, sure, and yes, it was great.

But I find myself watching the reactions so much more.

My favorite is the one shot by ESPN's Kaylee Hartung. Thousands of Villanova hands going up in unison … and then the explosion and disbelief as the shot goes in. That's raw, unfiltered human reaction right there.

You can never get enough of them. My favorites of recent vintage:

John Brooks scores against Ghana in the 2014 World Cup:

For that matter, Landon Donovan scores in the 2010 World Cup to clinch a spot to the next round:

Germans and Argentinians reacting to the 2014 World Cup final:

Oh, yes, the Cubs winning the World Series:

If Indians (or Cardinals) fans struggle with that, there are always these:

(That last one gets me teary every time.)

You can find these for just about any team, and if you're not careful, you'll fritter away most of your morning like I just did playing around with them. Sunday gave us another one. This coming Final Four might give us more. They are constantly replenishing. What happens on the field is just the instigating event. The way we react to it, how it makes us feel, can be more compelling than what is actually happening. Sometimes it's us who are the stars.

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Email me at leitch@sportsonearth.com; follow me @williamfleitch; or just shout out your window real loud, I'll hear you. Point is, let's talk.