Why are yawns
contagious?
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The full narration of the video.
Halfway through a meeting, the colleague across the table opens wide and yawns. A moment later, the person next to them yawns too. Then it's your turn. You clench your jaw to hold it in, but the harder you fight, the stronger it gets.
This video is full of yawns. If you start yawning, don't worry: you're part of the experiment. In 2014, Duke University in the US had 328 people watch three minutes of other people yawning. 222 of them yawned along. That's about two out of every three.
Most of the others weren't holding back. They just never felt the urge. So why do some people catch it instantly, while others never do? People say yawn-catchers are more caring. But Duke measured that too, and it didn't line up with who yawned.
Age mattered a little: younger people caught it more. But age explained less than a tenth of the difference. In 2017, the University of Nottingham in the UK looked somewhere else: the part of the brain that runs your movements. Picture it as a lever on a machine. Push the lever all the way down, and out comes a yawn.
A spring pulls the lever back up. For some people the spring is loose, and one touch sends it down; for others it's tight, and it barely moves. Every yawn you see gives your lever a push. The researchers used a magnetic pulse outside the scalp to tap this part of the brain, and saw how easily it lit up.
The easier it lit up, the more that person yawned at the videos. That explained about half the difference between people. Nottingham's 36 volunteers had some rounds where they could yawn freely, and some where they had to hold it in. Holding back made the urge stronger. All it changed was the look: a wide-open yawn became a stifled, closed-mouth one.
It's like holding the lever up with your hand while others keep pushing it down. Once the lever passes a certain notch, there's no stopping it. A yawn lasts about six seconds, and it's hard to quit halfway. And it's not only sight that pushes the lever. Hearing a yawn, reading the word "yawn", even just thinking about one, can give it a push.
The hardest pushes come from people you know. The University of Pisa in Italy watched daily life for a year: family spread yawns most, then friends, then acquaintances, and strangers least. We aren't born with this. Children under four rarely catch a yawn. So why are yawns catching at all? Scientists still haven't settled it.
Some think it helps a group wake up or wind down together, in step. Others say it's just a side effect of a very sensitive lever. Who gets you yawning more easily: your family, or your coworkers in a meeting?
In one line
Every yawn you see
gives your brain a push.
Fight it, and the urge grows.
Two out of three
will catch it
In 2014, Duke University in the US had 328 people watch a three-minute video of other people yawning.
Not what
you think
I'm more caring.
The lever
in your head
Picture the brain's movement area as a lever on a machine. Push it all the way down, and out comes a yawn.
There's no real lever in the brain: a movement area gets "lit up" while another force holds it back. So a yawn in a meeting doesn't always mean you're tired (for real tiredness, see why you're still sleepy after 8 hours).
Why fighting it
makes it worse
Nottingham had 36 volunteers watch yawning videos. In some rounds they could yawn freely; in others they had to hold it in.
It's like holding the lever up with your hand while others keep pushing it down. If you can't hold it, it's not bad manners.
Who pushes hardest
The University of Pisa in Italy watched everyday life for a year to see whose yawns spread most easily:
We aren't born with this: in a University of Connecticut study, children under four rarely caught a yawn.
Scientists haven't settled it.
Quick check
Why do some people catch a yawn right away while others never do?
Caring didn't line up with it; what mattered was how easily the movement area gets pushed. Loose spring, one push, yawn.
