Roman Atwood, a YouTube user who enjoys pranking people, decided to go big for his latest project: he travelled to various spots around the world... and made people yawn.
The whole video is great, but make sure you stick around for the two guys at the 1:15 mark - they're not falling for it.
So how did Atwood prank everyone? Simple: he just walked past them while yawning.
You may have noticed that when someone near you yawns, it can be nearly impossible to prevent yourself from doing the same, whether or not you're tired.
As for why that is, the jury's still out.
A 2010 study found that yawning might be a sign of empathy and a form of social bonding, according to Discovery.
The study was carried out by Molly Helt, a graduate student in clinical psychology at the University of Connecticut, after she noticed that her autistic son didn't copy her yawns while they were sitting together on an airplane.
"Emotional contagion seems to be a primal instinct that binds us together. Yawning may be a part of that," she said. "The fact that autistic kids don't do it might mean they're really missing out on that unconscious emotional linkage to those around them."
People aren't the only animals that yawn - in fact, all vertebrates, including snakes and lizards, do it.
But only people, chimpanzees, and possibly dogs (as demonstrated in the video) are prone to contagious yawning.
Robert Provine, a developmental neuroscientist at the University of Maryland, says human yawning starts early - fetuses begin to yawn as young as 11 weeks.
Here's a video from last year, using 4D ultrasound scans to show a baby yawning in the womb:
Babies may be yawners, but contagious yawning doesn't seem to kick in until a little later: Helt's study found that kids only start to "catch" yawns regularly at age 4.
"Yawning is a really big deal," Provine said. "We're dealing with something ancient, deep, and at the very root of our being."
And it's also useful for pranks.
Via Holy Kaw