We all yawn. When we’re tired, when we’re bored, when we see someone else do it. It’s so contagious, you’re probably wanting to yawn just thinking about it!
The simple question of why we yawn doesn’t have an easy answer. It turns out that while there are some strong theories about yawning, there’s still a lot we don’t know about this common everyday activity. It’s a fascinating subject, so let’s dive in and get the facts about yawning.
Before we try and answer the question why do humans yawn, it's important to understand what yawning is.
A yawn is an involuntary action where our mouths open and our lungs take in a large breath of air before they exhale it back out. At the same time, your eardrums stretch and your eyes will close, causing them to water. Typically, you’ll feel more relaxed after you yawn.
There are two leading theories around why we yawn. The first is that yawning is contagious due to our social bonds. You may have noticed that you mirror other people - if they give you a friendly smile, you’re likely to give them one back. Yawning may just be another example of that mirrored behaviour. However, the verdict is still out on this one, with scientists calling for more studies into whether yawns are contagious.
The other theory is that the underlying purpose of yawning is to regulate your temperature, or cool the brain down. In fact, studies have shown when you’re cooler, you’re less likely to ‘catch’ a yawn from someone else.
Let’s dig deeper.
When we’re tired, our brain and body start to cool down. Yawning at this point makes sense if it helps us with this cooling process, as this prepares our brain for sleep. Similarly, when we wake up we begin to warm up at a faster rate than any other time of day, so yawning could help to regulate this process too.
So if you start yawning at the end of the day, it’s probably a good sign to snuggle up on a comfortable mattress as you get yourself ready for sleep.
Yawning may not be entirely biological. Instead, it might be something you ‘catch’ from others, just by seeing or hearing them do it. As we discussed above, watching people yawning may stimulate your brain to mirror their actions to form a social bond.
Another theory is it has something to do with evolution and group behaviour. As yawning increases alertness, the idea is if one member of a group yawns, it could signal to the rest that it’s important to be alert.
Overall though, it’s still a bit of a mystery.
There are other reasons you might yawn that have nothing to do with being tired. If you’ve ever been in an aeroplane that’s taking off, you would have experienced the uncomfortable feeling that the shift in air pressure creates in your ear canal. By yawning, whether it’s intentional or not, you regulate the pressure within your ears so the pressure inside matches that on the outside.
You also yawn when you’re bored or hungry, which may be a way for your body to signal that you need to act in order to fix the situation.
Yawning during exercise may seem counterintuitive, but it makes a lot of sense in terms of temperature regulation in the brain. As you exercise, your body heats up, and yawning can help to cool it down by increasing blood flow to the brain.
To break the process down, when you yawn, you open your jaw and stretch your face muscles, increasing blood flow to the head. The intake of air forces spinal fluid and blood down from the brain, and the cool air you’ve breathed into your lungs acts to cool this fluid.
So what about excessive yawning?
Humans yawn around 5-10 times a day, so if you find yourself yawning more than this, you may feel it’s a lot. You don’t need to worry though, as too much yawning isn’t dangerous in itself. That said, it’s always good to go get a check-up if you’re worried to rule out any possible underlying health conditions.
Yawning and anxiety can go hand-in-hand, so this might be a possible cause as both anxiety and stress cause the brain to heat up. So if you’re about to give a big presentation and feel those butterflies in your stomach, don’t be surprised if a few yawns accompany them, too.
You might also be excessively tired and your body is trying to tell you! A comfortable and inviting bed is the best place to start if you’re feeling tired and can’t seem to stifle those yawns.
Hopefully you haven’t yawned too much while reading this, and have taken away some useful knowledge about why we yawn. And if you’re a little bit sleepy and want to learn how to fall asleep fast, we’ve got an article just for you!