Why Are Yawns Contagious? The Secret of the Copycat Yawn

Someone in a meeting lets out a huge yawn, and a few seconds later people around the room are covering their mouths. Even seeing a photo of someone yawning, or just reading the word “yawn,” can set you off. Is your jaw already itching as you read this?

Everyone yawns, and starts very early

Humans aren’t the only ones who yawn. Dogs, cats and monkeys do it, and so do many other animals with backbones, including birds and fish, in a yawn-like way. Ultrasound scans have even shown that people yawn before they’re born, in the womb.

So why do we yawn?

For a long time, the popular explanation was “we yawn because we need more oxygen.” But in experiments, breathing extra oxygen or extra carbon dioxide didn’t change how often people yawned much. So many researchers now think that explanation falls short.

Instead, here are some of the ideas being discussed.

• Cooling the brain: Taking a deep breath and stretching the jaw wide changes the flow of blood and air to the head, which may help regulate brain temperature.
• A signal for changing states: We yawn a lot when our state is shifting, such as waking up, getting ready to sleep or feeling bored. In this view, a yawn is a kind of switch that helps us become alert again.

There’s still no single agreed answer, so yawning remains a curious behavior even to scientists.

Why yawns spread

Contagious yawning has been confirmed in many experiments. Watching someone yawn, hearing a yawn or just reading about yawning can make you yawn.

What’s interesting is that it depends on whose yawn it is. One study found that yawns spread more easily from acquaintances than strangers, from friends than acquaintances, and from family than friends. That led to the idea that contagious yawning may be linked to social connection or empathy: naturally tuning in to the people around us.

That said, it’s hard to claim that more empathetic people always catch yawns more easily. Results vary from study to study, so the debate is still going.

What about kids and dogs?

• Young children rarely catch yawns, but researchers have observed that they start to as they grow. It’s intriguing that this lines up with the age when children get better at understanding what others are thinking.
• Some studies suggest dogs may catch their owners’ yawns. The results are mixed, though, so for now it’s best to say “maybe.”

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In one line

We still don’t fully know why we yawn, but contagious yawns may reveal our social instinct to tune in to the people around us. Try counting how many times you yawned while reading this!

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