Yawning Has Nothing To Do With Our Lack Of Oxygen

“Many things are said to be passed on. Sleepiness can be passed on, and yawning can be passed on. Time can be passed on also.” —Miyamoto Musashi, The Fire Book

In A Nutshell

We all yawn, and now we know we even do it before we’re born. And we’ve all heard that we yawn because our brain is getting a bit oxygen-starved, and the massive inhale is a pick-me-up for the brain. Only science has found that it’s not true—the real motivation behind yawning is that the air intake acts as a cooling system for the brain, helping it work more efficiently.

The Whole Bushel

Yawning is another one of those long-standing biological mysteries. The typical reasoning behind why we yawn is that we’re tired, and our brains need the extra oxygen drawn into our system during the yawn in order to stay awake. Turns out, that’s not exactly how it works.

Yawning does impact the brain, but it’s not the rush of oxygen that matters. When you yawn, you’re inhaling more than oxygen, you’re inhaling air that’s cooler than your body temperature. That air gets funneled into your sinuses, which then push the cooler air over the brain; yawning is essentially a cooling system for your head.

There have been a number of different theories on why we yawn, but this is the only one that stands up to scientific scrutiny. It also answers another long-standing question: What the heck is the point of our sinuses, besides giving us headaches?

It turns out that the air intake and the physical act of yawning all work together; it isn’t just enough to get the rush of air to lower the temperature of our brains. Opening your mouth to yawn makes the walls of the sinus flex, and they act as bellows to push the air through the cavities in your head.

The theory has been backed up in medical research conducted on rats. Researchers have monitored their brain temperature in conjunction with their yawning, and have confirmed that whenever there is a jump in temperature, the rats will yawn to help lower it. People who have the ability to predict their yawns have also participated in studies that confirmed the hypothesis works in humans, too.

That also leads to the question of why we have the overwhelming urge to yawn when we see someone else do it—almost certainly, brain temperature can’t be contagious, can it?

The answer seems to be a vague “Sort of.”

Our brains function most efficiently when they’re at a yawn-cooled temperature—it’s why we might yawn when we first get up in the morning, to help speed the waking process. But it’s also why we might be hard-wired to see yawning as a signal that there’s some reason you need to be awake and functioning at your best. When you see someone yawn, that’s a sign that there’s danger, that something’s approaching, or there’s some other reason that you need to be at the top of your game.

And since yawning is silent—for all but the most dramatic among us—that also works with the theory that yawning is a type of in-the-face-of-danger communication.

Interestingly, chimpanzees are the only other animal that has demonstrated contagious yawning. And while they’re frequently afflicted with it, the idea that humans are all subject to yawning when we see someone else do it is also a myth—in fact, only about half of the human population can’t resist joining in when they see a yawn.

Show Me The Proof

BBC News: Why is yawning contagious?
National Geographic: Why Do We Yawn? It May Keep Us From Getting Hot-Headed
Smithsonian>: Why Do We Yawn and Why Is It Contagious?

  • Nomsheep

    That kind of makes sense, but if infectious yawning was a survival thing, why are the numbers so even between people who have to join in, and people who don’t?

    • Lisa 39

      Natural selection?

      • Nomsheep

        That doesn’t explain the 50/50 split, the rate of people who mimicked the yawning should be a lot higher.

        • Lisa 39

          Maybe the 50% who don’t mimic yawning are the ones selected to not survive, its just unnatural to not yawn when others do it, but since we’re stubborn humans we just survive anyway 🙂

          • Nomsheep

            Then natural selection is a lie!

          • Lisa 39

            O snap, I didn’t mean to start a revolt against sciency stuff lol

            Off topic: speaking of natural selection, I own a CD titled natural selection by a group called fuel, hemorrhage is an awesome song!

          • Nomsheep

            Science has betrayed me ;-;

            *goes to youtube to listen*

          • Lisa 39

            (Just don’t tell the christian hating atheists that the kinda religious woman destroyed science for you, I’m not up for an attack right now 😉 )

            I hope you like the song, I guess I could have posted it

          • Nomsheep

            but, but I already made the call… it’s too late now.

            yep, it’s pretty cool ^_^

          • Lisa 39

            Crap, time to turn off my Wi-Fi on my phone I guess, sorry for crushing your world nom, the upside is that now you’re free to be a religious nutter who believes that the world is only 6000 years old!

            I’m glad that you liked it 🙂

          • Joseph Wilson

            Wait! The world is older than 6000 years? Dammit! Jeebus lied to me!

          • Lisa 39

            Calm down fluffy cheeks, nobody lied to you, men just aren’t perfect 😉

          • Yeh men are scum women are perfect

          • i liked it very much

          • Nathaniel A.


            In short, along with the mutations that help you and the ones that harm you, there are some that have a neutral effect.

          • Lisa 39

            Thank you for the link Nathaniel, but I swear I’m not a mutant! If I was I’d join the x-men 😉

          • Thanks for the link Nathaniel

          • It is an awesome song

          • Maybe

      • Natural selection

  • Koki

    As I yawn

    • Lisa 39

      Try some coffee, that should help, or a glass of ice water, I hear that it speeds up metabolism;)

  • oouchan

    So my brain is hot? Ok. We are machines with a few flaws. Like the idea of the cooling system.


  • Peter

    I can’t even read the word with out doing it!

  • dysamoria

    Several other yawning articles clearly state that other animals experience contagious yawning. One example is canines. http://m.nydailynews.com/life-style/health/yawning-contagious-animals-study-article-1.1920127

  • JEFF_777

    If yawning is to cool the brain, wouldn’t everyone out in the desert, on the beach etc. be constantly yawning???