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It's a story as old as time - someone else around you is tired and lets out a massive yawn, then within a matter of seconds you find yourself fighting a seemingly unstoppable urge to yawn yourself.
But, have you ever stopped to think about why that might be?
To begin with, did you know that the average person yawns 20 times each day?
Most people assume that we yawn to get more oxygen into ourselves, and scientists thought the same until a few decades ago.
However, back in 1987 a study was published that showed there is no correlation between the urge to yawn and oxygen deprivation.
So, today the main theory is that it is for arousal.
No, not that kind.
As we start to tire, particularly if we're watching something super boring, our body yawns to give us a little kickstart.
Dr Reyan Saghir, an academic surgeon, told publication Real Simple: "As we become tired, especially when viewing uninteresting or non-interactive repetitive stimuli like a lecture, our body yawns as a means to 'wake up'.
"Studies have shown this to be true where an individual's heart rate can be seen to rise and peak for 10-15 seconds post-yawn, similar to a kick of caffeine."
As for why we do it when others do, the likely reason seems to be empathy.
Dr Saghir added: "As humans age, we enhance our psychosocial and neurological development, taking other individuals yawning as a cue that we should yawn as well."
This strange quirk of the body is called echophenomena, and isn't only observable in humans.
In fact, chimpanzees and dogs have been seen to yawn when others do, too.
Now that you've thought about that, you've seen them do it, haven't you?
It's just a natural response, as our brains are wired up to copy those around us.
Saghir said: "Studies have shown yawning triggers the 'mirror neurons' in the right posterior inferior frontal gyrus of the brain, which are activated when performing goal-directed behavior for true imitation, making the yawning reflex physically impossible to resist as our brains are wired not to.
"As mentally healthy adults, our psychosocial development will make us yawn when others do. But in individuals lacking the correct mental development, the contagious effect of yawning is not seen.
"For instance, studies in children who are still developing the neural mechanism were only found to yawn in tiredness and not in response to another yawning. Similarly in adults with conditions like autism or schizophrenia, in which social development is different, yawning was not reciprocated."
Furthermore, how close you are - emotionally, not physically - to the person yawning could have a role to play, too.
Dr Saghir continued: "For example, if a family member yawns, you're more likely to yawn compared to a stranger - this is because of an empathic link our brains make that we empathize with the person yawning more and want to mirror their actions unintentionally."
There you have it, aren't you glad you've learned that?
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