We dare you not to yawn while reading about why yawns are a thing
You're probably about to yawn. A lot.
And it's not a sign of weakness. Yawns are so contagious that just talking about them can set us off, and some scientists think they're a form of communication that helped our ancestors go to bed at the same time.
We do it in the womb, and people in comas even yawn automatically. Despite their frequency, scientists can’t seem to agree on why exactly we do it, and there are multiple theories.
If you’ve not yawned already: congratulations, and good luck keeping up that streak.
We don’t just yawn when we’re tired, it can also happen when we’re stressed. Athletes often do so before big races and paratroopers have a quick yawn before they jump out of planes.
Security agents in US airports are even told to look out for passengers who yawn excessively, as it might hint that they're up to no good.
This link between stress and yawning might mean it's a displacement activity – a seemingly unconnected behaviour animals do when faced with a difficult decision, or when their environment stops them doing what they really want to do.
Human displacement activities include head-scratching and phantom beard-scratching, while birds are sometimes seen pecking the ground during fights.
Yawning is air con for your brain
Other researchers think there's a physical reason behind our need to yawn.
Andrew Gallup, a psychologist at the State University of New York at Oneonta, thinks yawning is a brain cooling mechanism, like the fan in a computer.
He argues the movement changes blood flow and draws heat away from the brain, brings a breath of fresh air to the relevant arteries, and ventilates the sinuses by evaporating mucus which has the same cooling effect as sweating.
Gross, but useful.
A group that yawns together, stays together
Why is it so contagious? Around half of us will yawn if someone we're talking to does, but pictures of the act or even talking about it can also trigger us.
Regardless of whether it's due to stress, tiredness, or temperature, its spread between people is likely to aid communication.
If a prehistoric human was tired, worried or cold, there was probably a stressful event or cold snap that would affect their whole group. Spreading yawns were probably a good thing because a synced up group is a stronger one.
If you don’t, there might be something wrong with you
Studies have shown that people who don’t yawn in response might be down right psychopaths.
Research published in the journal Personality and Individual Differences in 2015, showed that people who didn’t catch yawns as easily were more likely to have psychopathic tendencies.
People who don’t yawn back aren’t necessarily fully blown psychopaths, but it does suggest a lack of empathy.
So if you’re trying to make friends with someone, mirroring their yawns when you talk to them might be a good start.
How to stop
If you find yourself doing it incessantly when it's socially unacceptable, there are some things you can do to stifle your need to yawn.
Gallup found breathing through the nose stopped people succumbing to the urge, which could be to do with the incoming cold air, removing the need for a brain-cooling yawn.
His team also found that holding a cold compress to the forehead had the same effect, so you might try taking a brisk walk outside or sticking your face out of a window to chill your brain down a bit.
Scientists haven’t come to a consensus on what makes us do it, but yawning does probably serve some kind of purpose.
So if you’ve got through this without doing it, you're impressively stubborn, but might not have an evolutionary advantage.