Why We Yawn, And Why It's So Contagious

Your grandmother says it's because you watch too much TV. Your teacher thinks it's because you're bored. And that creepy guy on the bus just slapped you with a phonebook in an attempt to exorcise the devil living in your molars. All because you're yawning.

There's got to be a better explanation, right?

Scientists haven't nailed down the exact cause of our 240,000 lifetime yawns yet, but there's good support for the yawn as a temperature regulator. In 2007, researchers at the University of Albany showed students a video of people yawning. Half the students were instructed to breathe through their nose, and the other half were told to in and exhale through their mouths. Of the mouth-breathing group, half of them yawned at the video, but among nose breathers, yawning was pretty much non-existent.


It could be that the mouth-breathers were overheating their grey matter. Because the brain burns up to a third of our daily caloric intake, it generates a bit of heat. And our brains work better when they're not too toasty.

To help keep the temperature down, blood vessels in the nasal cavity and face send cool blood to the brain. The thought is that breathing through the mouth doesn't allow the brain to be as efficiently cooled. When you yawn, it causes the expansion and contraction of the maxillary sinus, a cavity located in the cheek. The sinus shoots air upward, kicking cool air at our headspace.

In another test, the Albany researchers placed a cold pack, a room-temperature pack, or a warm pack onto each participant's foreheads. Those with the frosty domes yawned less than those in the other two groups. And last year researchers at Princeton found that we're less likely to yawn when the temperature outside exceeds our internal body temperature, supporting the theory that yawning has a thermoregulatory function. That 112 degree summer-in-Arizona air is bad for your mind, man!

But if yawning just keeps our brain sufficiently chilled, why is yawning the most contagious condition since the Black Death?

There's some research suggesting that yawning can hint at emotions ranging from interest and stress, to, um, the desire to get it on. The yawn as an indicator of arousal came up as a theory at the first annual International Conference of Yawning (yup), held in Paris (yup) in 2010, when a chasmologist (someone who studies yawning (yup)) pointed out that sexologists often get patients complaining about yawning in the lead up to -- and during -- sex.

The yawn ripple effect could also be an evolved response, with the function of keeping groups alert when it counts. Hanging out in bear country? If yawning is your body's way of increasing brain function, passing on a cool brain boost to the clan would be a smart move when you all need to be on the look out for danger.

While a whole host of animals yawn -- including snakes and fish -- not all of them are susceptible to the contagious yawn. Chimpanzees experience the domino effect. And dogs cannot only catch a yawn from another pup, but from a person, too. Researchers think it might signal a social connection in animals, and in humans, possibly empathy. There's research showing that friends and loved ones catch each other's yawns more readily than they do from outsiders.

For me, whether it's the time change or just an overheated brain, writing this article has sent me into yawn overdrive. Even the word has had ((YAWN!)) a repeated effect on me. Brb. Next week.

Rachel Swaby is a freelance writer living in San Francisco.

Image: Shutterstock/Yuri Arcurs

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    This study was done ages ago, and the reaon why we yawn is based on pack survival - in essense, if one person saw danger, they instintively yawn and the rest of the pack will follow suit. Yawning increases the oxygen in the blood flow to the brain making it more alert. This then means the pack is more alert to the danger, and able to react better.

      The study done ages ago didn't really fall in our laps, though, did it?

      Thanks Giz for passing it on. And for talking about the reduced brain function of mouth breathers. :)

        I thought it was common knowledge though

          Common knowledge isn't so common. Just like common sense is one of the greatest fallacies.

          Common knowledge has to make its rounds somehow.

      Stupidest thing I've ever heard. Who the hell yawns when they see danger?

        Maybe they studied silent film, and they were actually screaming?

      I don't agree with the yawning "on seeing danger" part. Yawning is kind of incapacitating/distracting for a moment, not a good idea when a tiger is about to eat you for lunch (or indeed eye balling you thinking of lunch). I do agree though that it is a function to give a temporary boost to alertness and indeed the same for the pack. It could even be a good signal that it's time for someone else to be on the lookout as this lookout is tired (it's would be wise for the pack to know that the lookout is tired and could possible fall asleep.) haha.

    The longer you look at the picture, the more apparent it becomes that she isn't really yawning.

      That comment isn't creepy at all...

        I'd yawn all over her.

        Oh, that was meant to say fawn, sickos ; )

      You may be right Benny. I'll have what she's having. lol

      If this was 4Chan she would have been 'shopped by now...

    How many people reading this article yawned before they got to the end, talking about yawning is almost as contagious as seeing someone yawn...

      I was yawning all the way through the article just from thinking about yawning, heck I'm still yawning.


      I just became way more away of how I was breathing through my nose.

    My understanding of the yawn is that is causes people to draw more air deeper into their lungs and actually hold it for brief period, and in doing so increase the oxygen levels of the blood. This makes sense when you consider that many people yawn when they've been lethargic, as during periods of lethargy our breathing is shallow. The lack of yawning among nasal breathers though certainly raises questions as to whether O2 levels are behind the yawn.

    As to why yawns are so darn contagious that's a bit of a pickle.

      This is what I thought or read somewhere, that when you're tired, your breathing slows down, and if you don't sleep, you're not getting enough oxygen to your brain, so you yawn, giving it a spike of oxygen.

    I yawn all the time. I also have developed asthma, I seem to yawn more now! I knew I wasn't getting enough oxygen! That and I always feel hot.

    Common knowledge, like no clue..

    Who spends money researching this stuff....

    Probably done on Free Fridays..

    yawned during comments. lol! But on Freak Geeks (?) (adam spencer and Dr.Karl) , when they talked about yawning, ON THE TV, I yawned. Go figure

    This isn't and answer to why we yawn or why yawns are contagious, just more theories. They simply add to the pile of studies, not replace them.

    isnt this an old article?
    I remeber reading it cause at the time me n my gf were debating why we yawn and i won cause of this article


    (the link is now dead)

    is this what giz does now just repost old articles?

      We brought this article back to the top of the feed because of Sleep Week.

    This article needs to be listed as old with outdated research. Don't mislead the people with incorrect information.

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