Why Do We Yawn When We’re Tired?

We yawn to cool our brains down.

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Yawning is one of the most common tendencies in the world. All humans, and even many animals as well, yawn. From babies to grandparents, everyone yawns. But have you ever wondered when and why we yawn?


The first thing that popped into your mind was probably that you yawn when you’re tired. It is true that people tend to yawn more when they’re tired. But why? Let’s find out.


There are actually quite a few theories that try to explain why we yawn. The most popular of these is the one put forth by two scientists, Andrew Gallup, and Gary Hack.


In their study in 2011, they found out that we yawn to cool our brains. They reasoned that brains were like computers. Computers have fans to cool down the central processing unit. This is because when the CPU works too much or for too long, it runs hot. When this happens, the CPU is cooled down to normal temperatures, so it can work well again.

Tiger Yawning
Cats, dogs, and even snakes! Yawning is one of the most common biological tendencies in the world. Credit: Wikimedia Commons/Ted

Similarly, even human brains need to be cooled down when they work overtime. We need to cool them down for them to work at their optimal levels.


This isn’t even the first time yawning has been tied to temperature control. As early as in Ancient Greece, a man named Hippocrates noticed that people generally yawn when they run a high body temperature. He also noticed that when we yawn, we take in a very large amount of air.

Hippocratic Oath
Did you know that all doctors have to take something known as the Hippocratic Oath? This is because Hippocrates is widely considered as the father of modern medicine. Credit: Wikimedia Commons

Yawning lets us better manage our brains’ temperatures. This also makes sense as to why we yawn more when we’re sleepy, tired, or exhausted. In these instances, we are essentially moving to periods of rest. Usually, these periods of rest are preceded by periods of work.


For example, when you go to sleep at night, chances are you’ve worked, studied, or played during the day. We yawn to cool down our brains during or immediately after these mental stimulation periods.

Do We Only Yawn When We’re Tired?

Actually, no! Yawning is often pigeonholed into being a response to tiredness or drowsiness. However, it’s actually a pretty well-rounded biological response to multiple different kinds of situations.


For example, did you know that humans also yawn as a means of communication? A study at the University of Cincinnati found out that when humans get overwhelmed with their emotions or are confronted with a conflict they do not want to deal with, oftentimes they will yawn rather than verbalize their feelings or emotions.


(Fun Fact: The same study also found out that men yawn more than women. The author believes that this is because women are generally more socially aware than men.)


Although it is widely well-known that yawning is contagious , research into why people (and animals in general) yawn is still pretty under-studied.


However, we do know which chemicals in the brain are responsible for yawning.


Neurotransmitters like serotonin, dopamine, glutamic acid, and nitric oxide have all been identified as possible culprits as to why we yawn.

Neurotransmitters, represented by dots in this diagram, are molecules that are enclosed in larger vesicles and jump from neuron to neuron through synapses. Credit: Wikimedia Commons

Yawning is also linked with high levels of cortisol, a stress hormone . Cortisol levels in the body generally rise when we’re fatigued, tired, or stressed.


So far, we know that humans generally yawn when we’re tired, stressed, or drowsy. However, the bigger conclusion to draw is the fact that humans seemingly yawn anytime we’re faced with an uncomfortable situation.


Contagious: Can be passed from one individual to the next.


Neurotransmitters: Chemicals in the brain that are responsible for how we behave. For example, your mood, appetite, and even your feelings or emotions are all based on the neurotransmitters in your brain!


Hormone: Hormones are chemicals in your body that travel through the bloodstream to transfer messages from one part of the body to another.

Readability: 64.6


Flesch Kincaid Grade Level: 7.7


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