Why Do We Yawn And Why Is It Contagious?

girl yawning

Everybody does it. Sometimes it’s early in the morning, sometimes it’s the middle of the day and your at work or school and sometimes it’s at night. So what actually causes us to yawn?

Yawning is an involuntary action and once you start it’s pretty hard to stop yourself. A yawn is a coordinated movement of the thoracic muscles in the chest, diaphragm, larynx in the throat and palate in the mouth. It coats the lungs with a wetting agent (surfactant) to coat the alveoli (tiny air sacs) in the lungs. We generally cannot yawn on command and it is triggered by neurotransmitters in the hypothalamus of the brain.

Surprisingly even with all the time, science and technology we have today there isn’t a definitive answer! Yes believe it or not, we STILL don’t know exactly why we yawn! There are several leading theories but there aren’t any proven facts that highlight one above others.

Let’s go through a few of the main theories.

Yawning Gives Us More Oxygen And Releases Carbon Dioxide

There are theories on this benefiting the respiratory and circulatory system. Could we need more oxygen in our lungs or do we need to expel more carbon dioxide that has been building up?

Modern day evidence makes it seem unlikely that yawning is a function of the respiratory system though. The circulatory system however could be affected by yawning to increase blood pressure, heart rate and oxygen in the blood thus improving alertness and motor functions.

Yawning Cools The Brain

Recent studies have suggested that yawning could be related to brain temperature (Gallup and Gallup, 2008). Basically when the brain goes beyond the normal temperature, yawning could cool the brain. This may involve the body’s cooler blood flowing into the brain and warm blood circulating out through the jugular vein.

An odd contradictory in my opinion is that you are more likely to yawn in colder temperatures such as winter than in the warmer summer which I’d expect the opposite considering the environments temperature should affect a body as well.

Yawning Stretches The Lungs And Lubricates Them

The idea here is that stretching and yawning may be a way to flex the muscles, joints, increase your heart rate and feel more awake.

Along with this is the theory that yawning is a protective reflex that redistributes surfactant (oily substance) that helps lubricate the lungs and keep them from collapsing. This is supposed to suggest that if we didn’t yawn, taking deep breaths would become increasingly more difficult as time goes on.

Yawning Indicates A Change In Behavioral State

This would be associated with the change from wakefulness to sleep or boredom to alertness for example. This could potentially have a correlation with physical states as well, such as going from exercising or doing some activity like walking to sitting in a chair and not moving much for an extended period of time.

group yawning

So How Come Yawning Is Contagious?

This is an extremely interesting concept and one that tends to be true. If you are in a classroom or in a group of people somewhere and you visibly yawn, more than likely other people will yawn within 5 minutes of you. Even thinking about yawning can start to trigger this contagion.

One idea is that it is a physical signal that our bodies are saying it’s time to sleep or get up kind of like an internal 24 hour clock. If one person is yawning and then other people start yawning because of it, then they all may go to sleep around the same time and thus have a synchronized cycle.


The truth regarding yawning is that it is still a mystery. Even after all the time passed and resources available to us, we still don’t know everything about the eluded “yawn”. Most the theories seem logical and possible so it’s very interesting that a large scale official study has not been conducted to get the 100% correct scientific truth.

For now I’ll just say we yawn because our bodies are telling us we need more sleep to function properly, but that’s just me!

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  1. I read that among animals – dogs – yawning is a social calming signal meaning: “hey, calm down”. I tested it with a cat and a dog, both will yawn when I fastly move towards them. If a dog yawns in return to his fellow yawning, it means “I accept your request and I calm down”. Maybe humans do the same at times?
    This calming signals thing as concerns dogs seemed to me not totally scientifically proven… but in practice I tested it and it worked. ;)

  2. Thank you so much for summing up the research there. I have been wondering abuot this for ages, as well as the hiccups! Love your blog!

  3. I once read there was a link between those in the human population who empathise and yawning. Never believed it to be true, although imagine if it was! Great read.

  4. Hahaha I yawned just reading the title! :O

  5. While reading this I ended up yawning 3 times. Though I yawned before I started reading also, probably because I am tired right now.

  6. Now I know I know… fer sure…

  7. *Yawning*… couldn’t stop yawning!

  8. It is a mystery. Even the photo made me yawn!

  9. I’ve yawned twice while reading this… oops make that three times. Seriously. It’s totally contagious. Love this post! Thank you for liking my blog posts!

  10. This post made me yawn…NOT because it’s boring, but the pics just made me yawn.

  11. HA! I really enjoyed this. Thank you for the smile at this unusual approach to information ;)

    ~Julius P.

  12. Great blog, the facts are as i had always believed. There is another one that`s contagious and that is an itch. sit next to a group and scratch,before long most of them will be doing the same as they think they also have an itch. :-)

  13. Yawning is so contagious, and it only takes one person to start it off. Great article!

  14. I think all science is just theory! a bunch of random guessing. every stupid study they do, they pull only the “facts” that they want to be there, and use those to make their point. and by the way, I just yawned!!! hahahahaha

  15. I thought the person yawning was bored…just saying.

  16. Great Post!

  17. I can’t think of a better post to read first thing on a Monday morning!

    Now for some coffee so I can stop yawning :-)

  18. I could hazard a guess as to why we yawn. Physiology of the human body fascinates me as did your post. I’ve heard many different reasons as well as to why we yawn, but the need for oxygen in the blood seems the most succinct. When we rest, our metabolism slows. Our breathing slows and when we suddenly decide to move, our muscles have more need of oxygen than they did in the restive state. It’s a oxygen deficit response in the body. If we are restive and reading, our brain needs the oxygen and it’s why I can’t stop yawning when I’m studying in or sitting in class learning. However, it’s only a semi-unconscious response to the oxygen depletion and as you said, thinking it can trigger it. So, when one person yawns and another witnesses it, the first yawn makes the others think of the yawn which triggers their response as well.

    To fall asleep, we have only but relax. Once our metabolism and brain function reach as certain lasitude, we fall asleep. Because of this, the amount of oxygen we take in is low. However, as we near sleep, our subconscious becomes more active, requiring additional oxygen as it sub-stimulates the mind causing us to yawn. The only flaw in my observation that I can see, is that why we sleep, we never yawn, but this could possibly mean that it is a higher brain function which is available only when we are awake and is unavailable when we are asleep.

    Interesting article my friend. I enjoyed it immensely.

    • An interesting article and the photos are funny too. All I know is this…, I always ‘feel good’ when I yawn, it’s a very relaxing behavioural response. If I see someone yawning, I tend to take on some of their energy too. For example, if they are yawning because they feel tired, funnily enough I start feeling tired.. Or if they yawn in a way that conveys they are relaxed, then I tend to feel relaxed in their company too. It’s very catchy!

  19. I learned this years ago in my Physiology class. Wow! Thanks for reminding me! Great post!

  20. I was always told that people yawn to get oxygen to the brain….. that is what i always thought :)

  21. LOL I instantly yawned when I read the headline. :) Thanks for the fun information!

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