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Why do People Yawn?

flu3nce

New Blood
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Feb 9, 2004
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My professor assigned a take home project in which we must answer a given question for a test grade. He allows students to bring in whatever information they can find so that he can tell them whether or not their information is correct, yet only two students have gotten their question right.

My question is "why do people yawn."

It apparently has nothing to do with an oxygen shortage, and it's not a habitual display of disinterested as one teacher suggested. Please help.
 
The only thing I can note is that -- in my mind -- the answer must almost certainly be physiological, more than social. Other species [cats] yawn, not just humans.
 
A yawn is a prolonged exhale.. It is a response to an excess of carbon dioxide in the lungs, that accumulates when we do not exhale deeply enough..

( I read that somewhere )

I'm not sure how it relates to the fact that yawns seem to be visually contageous..
 
Diogenes wrote:
It is a response to an excess of carbon dioxide in the lungs,
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not lungs. In the blood.

Breathing rates are a result of CO2 build up. Not O2 depletion. CO2 combines with H2O in the blood to form a weak acid. You brain detects the slight pH change and increases your heart rate/breathing rate. If you had to wait for O2 levels to go down before your body responded, you wouldn't be able to do much without passing out.

As far as yawning?....hell, I don't know!;)
 
Wrath of the Swarm said:
Ah, the Mad Scientist network. Is there anything it can't do?
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Wow, thanks for the link.

There goes all my free time :D
 
flu3nce said:
My professor assigned a take home project in which we must answer a given question for a test grade. He allows students to bring in whatever information they can find so that he can tell them whether or not their information is correct, yet only two students have gotten their question right.

My question is "why do people yawn."

It apparently has nothing to do with an oxygen shortage, and it's not a habitual display of disinterested as one teacher suggested. Please help.
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Er, I have always heard that yawing is due to way the body restores the oxygen/carbon dioxide balance; which is why it occurs when one forgets to breathe properly (as when one is tired or pre-occupied with something).
 
There is at least some research on humans to suggest that neither hypoxia (low O<sub>2</sub>) nor hypercapnia (high CO<sub>2</sub>) are responsible for yawning.

Truthfully nobody knows why we yawn. There may be a good physiological reason for it (and it is highly preserved) but on the other hand it could just be a spandrel.

Sorry not to be of more help.
 
I remember reading something about this but I really can't remember the source. The details I remember are also sketchy.

There was an article somewhere, somewhen which claimed that the yawn was actually something to do with temporarily increasing blood flow to the brain. In general terms their point was that we yawn when we need to either switch between mental activities, get our brain ready for something or just wake ourselves up a bit.

I really wish I could remember more about it.

I also remember that yawning could be triggered by seeing another person yawn or, in fact, just thinking about yawning. How many times have you yawned so far whilst reading this thread?
 
Scientific prediction: Most everyone who has read this thread or responded to it has yawned at least one time.
 
Camillus said:
Truthfully nobody knows why we yawn. There may be a good physiological reason for it (and it is highly preserved) but on the other hand it could just be a spandrel.
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It's an evolutionary adaptation to prevent men from throwing bricks through the television screen when their girlfriends force them to watch The English Patient, which would otherwise lower reproductive success.
 
Perhaps to stretch the jaw muscles. We often yawn when we stretch other muscles. When we see someone yawn we feel like yawning ourselves, so probably it has some social effect too.

I wonder if social animals yawn more often than non social animals. I know lions & dogs yawn. They are a social animals. I have yet to see a cat yawn.

PS. I have yawned 5 times while writing this response. ;)
 
plindboe said:
Perhaps to stretch the jaw muscles. We often yawn when we stretch other muscles. When we see someone yawn we feel like yawning ourselves, so probably it has some social effect too.

I wonder if social animals yawn more often than non social animals. I know lions & dogs yawn. They are a social animals. I have yet to see a cat yawn.

PS. I have yawned 5 times while writing this response. ;)
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Cats yawn all the time. And they usually reveal a pretty awesome set of gnashers when they do.

I think at least part of it must be a social thing - a way of saying "I'm relaxed and comfy, it's safe here, shall we have a kip?".
 
richardm said:
Cats yawn all the time. And they usually reveal a pretty awesome set of gnashers when they do.
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Ah, ok. I'm allergic to the little critters, so haven't got much catsperience.
 
I'm not sure if this is off-topic, but modern respirators, of the kind they hook you up to in the hospital when you are in a coma or something, have a yawn/sigh circuit built into them. This is because it was discovered that if you force regular breathing into people, they die a lot faster.
 
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