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Why do we yawn?

  1. Apr 19, 2005 #1
    Evening everyone,

    This is a rather odd question: why do we yawn? Is there any biological reason for it? Why do we yawn when we see other people yawn or think about it?

    Oh, just typing this post is making me yawn! :zzz:
  2. jcsd
  3. Apr 19, 2005 #2
    Isn't any one going to try to answer? How about speculate?
  4. Apr 19, 2005 #3


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    The theories I have heard relate to either flushing carbon dioxide out of the lungs (although any deep breath will do this), or exercising the jaw muscles. I also read one theory that the yawn has only a social function, to alert others of our mental state.

    No one knows why yawning is contagious, but, indeed, seeing others yawn or even thinking about yawning makes one more likely to yawn. My own personal theory on the topic (PF posting guidelines be damned!) is that a population is safer and more productive when its members are following the same sleep-wake schedule. Yawning helps keeps members of a population (wild dogs in a pack, say) on the same schedule, so they can work better as a team.

    - Warren
  5. Apr 19, 2005 #4
    Try this page for more info.
  6. Apr 19, 2005 #5
    When in doubt...google. Here are three theories that could explain yawning.
    I've heard of the physiological theory. It makes the most sense to me. I notice they don't mention anything about increasing the carbon dioxide levels in their experiments. Yawning expands the lungs and increases heart rate accelerating the body's oxygen level in the blood and clearing the lungs of CO2. There is no need to yawn when excercising because there is already good exchange of O2 and CO2. I notice that I yawn when my breathing is shallow and maybe I just need a good breath. The contagious aspect may be psychological.

    Free divers have a similar procedure for clearing the lungs and oxygenating the blood. They don't yawn but it looks like several deep yawns performed very quickly. It increases O2 in their blood and expands their lungs to the maximum. They also learn techniques to influence their heart rates to conserve O2.

    Enough speculation?
  7. Apr 19, 2005 #6
    Yeah, I would say relaxing the jaw muscles and the carbon dioxide thing would be the foremost reasons. Also, as was said before with the wolf thing, systems are more efficient when neighbors pay attention and copy eachother. Another reason I have not seen mentioned, which may be incorrect but I will try to take a stab at it anyway, is to build rapport. Ever notice when you are in a classroom and all is quiet for a few minutes and a person coughs and a few seconds later another person coughs (its kind of creepy when you hear it in action)?

    Correct me if I'm wrong, a lot of things I said were mere speculations.
  8. Apr 20, 2005 #7
    That is plenty of good speculation. Thanks Huck. :biggrin: It is kind of creepy when you hear that in a classroom KC. I agree Warren. People who run on the same schedule do seem to work better as a team. Granted this is not true for every case. But that applies to just about everything.
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