Yaaaaaaawn. When it comes to yawns, two things are certain: Everybody yawns — and nobody really seems to know why.

We begin yawning very early in life — before we’ve even entered the world, to be exact. Ultrasounds have discovered that fetuses begin yawning and hiccuping as early as 11 weeks into their development.

There are several theories about why we yawn. One theory suggests that we don’t breathe as deeply when we’re bored or tired as we do when we’re excited or exerting energy.

When our breathing slows, our bodies receive less oxygen. This reduction in oxygen makes us feel tired and lethargic.

Yawning helps bring a burst of fresh oxygen into the blood while pushing carbon dioxide out. If this theory is correct, yawning is an involuntary reflex.

More recent research suggests yawning may be a way our bodies distribute oily substances called “surfactants” that lubricate the lungs and prevent them from collapsing as we exhale and inhale.

No matter which yawn theory you believe, one thing is for sure — yawning is contagious! If you’ve ever watched someone else yawn, it’s likely you’ve caught the yawn, too!

Scientists continue to study the “contagious yawn” phenomenon, but they’ve yet to conclude exactly what causes humans to yawn simply because they see another person yawning. Interestingly, their research has found that, like humans, chimpanzees will yawn when they see another chimpanzee do so.

The next time you get an urge to start a trend, just open up your mouth and yawn. You may be surprised to find the person next to you can’t resist the urge to join in, too.


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  1. It’s funny how sometimes reading about yawns or seeing someone else yawn causes us to yawn, too, isn’t it, “Wonder?” Thanks for leaving us TWO great comments! We’re glad you explored this Wonder of the Day®! :-)

    • Even thinking about yawning can cause you to yawn– how crazy! Thanks for sharing your comment, Matthew! We’re glad to have a great Wonder Friend like you! :)

  2. I was yawning like crazy in class today. I would do it every 5 minutes uncontrollably. Also every time I did my eyes watered. Think I ate too much turkey. ha ha ha.

    • Turkey can have that affect on us, Tyler J! We’re yawning just thinking about you yawning! We’re glad you have been WONDERing about yawning… but we’re off to bed! :)

  3. Hehehe! This video was super cool! And, I watched it in school with my friends because we wanted to know WHY we yawned so much in class! So we found this and we kept YAWNING and YAWNING until there were tears streaking down our faces but thats O.K cause we were laughing too, mostly! I’m glad we WONDERed!
    :) :) :) :) :)

    • Hey there Annie! We’re glad that you and your friends have a better understanding of yawning– and its power! We are yawning just thinking about yawning! :) We’re glad you WONDERed with us, too! :)

    • Well thanks so much, Kate! We are so happy to hear that you enjoy Wonderopolis! We’re glad you’re here with us, too! :)

    • It’s cool how that happened, Carlos! We think it’s WONDERful that you shared your yawning experience with your friends in Wonderopolis today! :-)

    • Oh boy, we hope we didn’t put your class to sleep, Madeline! We know the feeling… we’re yawning just READING your comment about yawning! They sure are contagious, but we’re glad you are still awake to Wonder with us! Thanks for sharing your comment! :)

    • We understand, BlueTooth! Scientists have a few ideas about why we yawn, but we do not know for certain…yet! Do you have a guess? :)

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Have you ever wondered…

  • Why do you yawn?
  • Is yawning contagious?
  • How do you make a dream catcher?

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Try It Out

Does all this talk of yawning have you feeling sleepy? A Native American tribe called the Ojibway believes that hanging a dream catcher in their bedrooms would protect them from bad dreams.

According to the legend, the center of a dream catcher allows only good dreams into the dreamer’s mind, while the surrounding web catches all bad dreams. When the sun comes up, the bad dreams trapped in the web disappear.

Want to make your very own dream catcher? The Dream-Catchers.org website offers detailed instructions. Put your imagination to work so you can catch some extra zzzzs while your dream catcher does some catching of its own.


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