It’s not a lack of oxygen! This is why we yawn

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When we’re tired, bored or stressed, we yawn. Or even when someone else does. What is known about the phenomenon so far?

We all yawn. But no one knows exactly why. What is clear, however, is that it’s contagious.

Who doesn’t know this: someone yawns heartily, and you already feel the impulse to yawn – even if you’re not tired. Maybe even now, as you read this, you suddenly have to yawn. But why is yawning so contagious? And why do we do it in the first place?

Most of the time, we yawn when we’re tired. But boredom, hunger or even stress can also be triggered. For a long time, the theory held that lack of oxygen in the brain is the reason for yawning. In the meantime, however, this theory has been disproved. It has also not been conclusively proven that yawning primarily serves as a wake-up call: The brain shows no other brain activity before and after yawning.

Nevertheless, many researchers assume that it makes us more alert. Among other reasons, this is because yawning can have a cooling effect on our brains. That’s because yawning stretches the jaw, which increases blood flow to the neck, face and head. Then a deep breath sends a gush of cool air into the brain. And that, in turn, can make us more alert.

But why do I let myself be infected when I am wide awake? Many researchers blame the mirror neurons in our brains for the contagious effect. These nerve cells are responsible for our compassion: We laugh when someone laughs and have tears in our eyes when someone cries. And we yawn when our counterpart yawns.

Researchers have also observed that particularly empathetic people are more likely to be infected. Another study found that it also matters what relationship we have with the person yawning: The closer they are to us – such as partner, friends or siblings – the more likely we are to be infected and open our mouths wide ourselves.

Another theory is that it serves group synchronization and thus promotes social cohesion, i.e. when everyone is tired, we feel closer to each other. By the way: Dogs also often start yawning, for example, when their mistress or master yawns.

Because yawning is not of great importance from a medical point of view, it has been little researched so far. Why we yawn and infect each other with it is still unclear. What is clear is that sometimes it just feels really good.