Can anyone tell me - - - why do we YAWN ?

Question

The other night my partner and i were watching tv and he started yawning, this lead him to ask the question - WHY DO WE YAWN ?. .... I could not answer his question but said to him that i would put it to Yahoo Questions, so can anyone answer this mystery ?

Answer 1

You're not the only one who doesn't know the answer to this one! Science still has not found a definitive reason for why we yawn. There are numerous theories out there though.

You can read a little summary of the theories out there at this website- http://www.howstuffworks.com/question572...

Answer 2

I've heard we yawn to get more oxygen to our brain to wake us up slightly.

Answer 3

I read in a biology book once that we yawn because our lungs aren't getting enough air. If you breath heavily, you will find that you don't yawn as much.

Answer 4

there are many theories out there but none have been absolutely proven, the first one that was excepted as fact was that we yawn because were not geting enough oxygen, and too much carbon dioxide, but it has been disproven.

it is wiered that we yawn... runners are observed to yawn before a race...  yawns are contagious... and fetuses yawn in the mothers womb.

one theory i read the other day was that the purpose of yawning was the regulate brain temperature.

i think it has quite alot of purposes: together with regulating brain temperature... i think its other purpose is to increase the heart rate (everyone knows that it increases heart rate, but do not think that its purpose is to do so)

when your tired (your hear rate decreases when your bored or tired), your body (brain or whatever) realises that your heart rate is slowing down, and so you yawn to speed it up. i therefore think it is a survival mechanism for survival, in that when our heart rates slows down our brains think were... dying.

another one of my ideas is that we subconciously know that our hearts will either decrease or increase while practicing certain activitites (like sleeping or running)

this theory proposes that when we yawn it makes the heart rate slow or increase depending on what activity you will do next. observe yourself one time... jump up and down and cause your heart to increase, and then purposely yawn (my heart usualy stabilizes faster than it would normally, although i have no instruments to prove this).

so this would mean that the hypothesis that the heart rate only increases would be wrong, although i have only observed myself, so i can not make that claim.

scenarios: 1) your going to sleep, your starting to relax, but your heart isnt slowing fast enough, so you yawn in preparation for sleep

2) just before a fight or physical activity your heart isnt beating fast enough so you yawn in preparation for THIS activity

i know there are two ideas here that contradict eachother, but both make alot of sense. read about it, research it, and think about it to reach your own verdict.

scientists havent come up with a reason for it p***e... so you know... i decided to come up with my owwwn :)

Answer 5

because when we are sleeping, our jaw bones have been relaxing too long so we need to stretch them just like we stretch out bodies when we have been sat down too long.

Answer 6

im pretty sure its all psychological. when someone else does it or even says it, the other person does it...it just triggers something!

Answer 7

Nobody really knows. We yawn when we are tired, but then why don't we yawn when we're running or doing exercise?

I've personally never found a satisfactory explaination.

Answer 8

I think a person yawns if there is too much carbon dioxide in their blood. This triggers something in the brain which in turn triggers a yawn. Yawning gets more air (and oxygen) into the lungs which then moves into the blood.

Answer 9

I seem to remember reading its becuse Co2 in the body builds up and triggers the response.

Its also a psychological response when you see others do it,