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I am going to warn you right now. Just by reading the title of this article, there is a very high probability that you are going to do it within the next two minutes.
You’re going to open your mouth impossibly wide, suck in a massive breath of air, stretch your jaw, and let out a deep exhale.
Yawning is one of the weirdest, most universal glitches in human biology. You do it when you are tired. You do it when you are bored. But most bizarrely, you do it just because you saw someone else do it across the room. Even dogs do it when they see you do it!
For centuries, science teachers told kids a very simple explanation: “You yawn because your brain is running out of oxygen.” Well, guess what? Science teachers were lying. Let’s look at the actual dream/” style=”font-weight: bold; text-decoration: underline;”>neuroscience behind why your jaw randomly unhinges.
The Big Lie: It Is NOT About Oxygen
In the 1980s, researchers decided to finally test the old oxygen theory. They put volunteers in a sealed room and slowly pumped in higher levels of carbon dioxide, artificially lowering their oxygen levels.
If the old theory was right, the volunteers should have started yawning uncontrollably to gasp for more air. But they didn’t. They just breathed faster. Yawning had absolutely no effect on their blood oxygen levels. The theory was completely busted.
The Real Reason: Air Conditioning for the Brain
So if it isn’t oxygen, what is the giant gulp of air for? The leading scientific theory today is that a yawn is basically a biological radiator fan.
Your brain is an incredibly power-hungry computer. It burns massive amounts of energy and, just like your laptop, it runs hot. When you are exhausted, or when you are staring blankly at a boring spreadsheet for two hours, your brain temperature slowly starts to creep up.
When you yawn, you stretch your jaw violently. This forces blood into the vessels around your skull. Then, you suck in a massive gulp of cool room air. That cool air rushes into the cavities behind your nose and physically chills the blood flowing up to your brain.
It is literally a mechanism to cool down your overheating hard drive so you can stay alert. The National Institutes of Health (NIH) has published several fascinating studies tracking brain temperatures dropping instantly after a massive yawn.
If the weird, hidden mechanics of the human body fascinate you, grabbing a copy of The Body: A Guide for Occupants by Bill Bryson will blow your mind. It explains all the bizarre things you do without realizing it.
Why is it So Contagious?
Okay, cooling the brain makes sense. But why do you yawn when you see me yawn? Why do you yawn when you just read the word yawn? (Seriously, how many times have you done it since starting this article?)
This is where psychology kicks in. Contagious yawning is linked directly to empathy.
Humans are deeply social pack animals. If one person in the tribe yawns, it signals that they are tired or losing alertness. As a subconscious survival mechanism, the rest of the tribe yawns to sync up their brain temperatures and stay alert as a group.
This empathy connection is so strong that scientists have found psychopaths—people who lack empathy—are actually much less likely to catch a contagious yawn. Even cooler? Your dog is closely bonded to you emotionally. If you yawn, your dog will often catch the contagion and yawn back!
Want to test this out? Set up a cheap Smartphone Tripod in your living room, hit record, and fake a massive, loud yawn in front of your family or your dog. Watch the video back and see how many seconds it takes for the contagion to hit them.
10 Sleepy Riddles to Test Your Alertness
Try to get through these without opening your mouth.
1. The Riddle: I am the wide-mouthed reflex you do when you are sleepy, bored, or just saw someone else do it. What am I?
The Answer: A yawn.
2. The Riddle: I am the biological computer inside your skull that gets too hot and needs a sudden gulp of cool air. What am I?
The Answer: The brain.
3. The Riddle: I am the old, busted myth that science teachers used to tell you—the invisible gas you supposedly needed more of. What am I?
The Answer: Oxygen.
4. The Riddle: I am the deeply human emotion of understanding how someone else feels, which causes the yawn to spread. What am I?
The Answer: Empathy.
5. The Riddle: I am the fuzzy, four-legged best friend who can actually catch a yawn straight from a human. Who am I?
The Answer: A dog.
6. The Riddle: I am the facial bone you forcefully stretch open to push cool blood up into your head. What am I?
The Answer: The jaw.
7. The Riddle: I am the specific type of person who lacks empathy and is highly immune to catching a fake yawn. Who am I?
The Answer: A psychopath.
8. The Riddle: I am the invisible, cool stuff that rushes into your nose and acts like a radiator fan. What am I?
The Answer: Air.
9. The Riddle: I am the specific state of feeling incredibly tired, which is the primary trigger for this wide-mouthed stretch. What am I?
The Answer: Exhaustion (or sleepiness).
10. The Riddle: I am the feeling of catching an action just by watching someone else do it, like a cold spreading through a room. What am I?
The Answer: Contagious.
The Wrap Up
Yawning isn’t just a rude sign that you are bored by someone’s story. It is a highly evolved, brilliant mechanism to reboot your overheated brain and sync up the alertness of your entire social group.
If you are obsessed with the weird psychology of human behavior, you should absolutely bookmark Psychology Today. Now, stretch your jaw, take a deep breath, and get back to work. Your brain is finally cool again.
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