A normal person yawns about 20 times a day. But why? Surely we can't all be so tired. But the reasons for yawning are not all about being tired.
Often, we seem to yawn because other people are yawning. Here are some facts on why we yawn and why it can be catching – even between dogs and humans, and over the phone!
Why do we yawn?
Yawning happens most often during times of change between waking and sleep. Think of a cartoon character starting their day with a large yawn, with outstretched arms and a gaping mouth.
But this isn't the only cause. We also yawn to be more alert, and sometimes because of increases in brain temperature. So we yawn to wake up and cool down our brains.
Why is yawning contagious?
There are some different theories about this. One theory says that if a person sees a certain behaviour, and they are sensitive to it, they will copy it. This is done by "mirror neurons" in our brains.
Some scientists think it is a kind of group behaviour that we have evolved because we live in groups like families. Out of our 20 yawns a day, many of them happen when we are with other people.
Contagious yawning could also be a way to help other people stay alert in times of danger. Because yawning can make us more alert, the idea is that maybe we evolved contagious yawning to tell other people when they should stay alert too.
When other people yawn, we also become more sensitive to how our own body is feeling. Maybe we are tired, but we don't know it until someone else's yawn makes us notice that.
Is a yawn catching over the phone?
It can be! Yawning is extra-contagious when it comes with a sound effect: that "ahhh" noise a lot of us make. If a person hears that over the phone, it might be enough to cause them to yawn.
Even this description might have made you yawn. That is how easily it can spread!
Is yawning contagious to dogs?
If a dog or cat lives in the same house as you, human-to-animal yawning can happen!
In fact, lots of other animals also have contagious yawning. Science shows that it is only social animals that do this. Dogs are a very social species.
What happens if you do not yawn when someone else does?
Some people are more sensitive to this than others. We are more likely to catch a yawn from friends than from strangers. Yawning only becomes contagious for us when we are four or five years old. That is when we begin to understand other people's emotions.
But there is not yet enough science to prove this. Some scientists think the real explanation for contagious yawning hasn't been found yet.
Fun facts
A yawn lasts about six seconds. When you yawn, you breathe in a lot of air, and then you quickly breathe out again. Your heart beats faster during your yawn, but we don’t know why!
Quick questions
- Why do you think yawning can make us more alert?
- Which species of animals are very social?
- Do babies experience contagious yawning?
