i used to think so until i saw my snake yawn.
as far as i know, there hasn’t been any explainations to why we and many other creatures yawn.
any takers?
also, any turtle specialists out there?
i also have 2 sliders who routinely faceoff and play peek a boo (covers own eyes with forelimbs repeatedly) until one turns and scurries away in a hurry. is this some sort of ritualized aggression to determine hierarchy?
Peppy!!
Easy - you get tired, not enough oxygen reache your brain, your brain triggers this reflex that forces your mouth to open wide and you inhale deeply, saturating your lungs and giving yourself mental relief. Anything else?
So when you’re running, is yawning a good idea to get more oxygen to the muscles?
Whatever would give you the idea that yawning is a ‘high function’?
You must be joking. But again, maybe you aren’t. I like Alessian’s answer. Here is another from the National Science foundation:
http://www.nsf.gov/nstw_questions/biol/quest057.htm
Yawning is a deep usually involuntary intake of breath through a wide open mouth often as an involuntary reaction to fatigue or boredom. (Webster’s Ninth New Collegiate Dictionary)
No one really knows if yawning is contagious or not. It has been a mystery among scientists for centuries. (L. Gene Hornsby, M.D., Director, Division of Child and Adolescent Psychiatry, The University of Texas at Houston, Texas)
Nobody knows why and there seems to be no speculation either. Yawning is a physiologic mechanism coming from being bored, sleepy, waking up slowly, etc. It is considered to be a slow breath. (Wayne Lawson, M.S., R.R.T., Department of Respiratory Care, UTHSCSA)
Yawning is psychological because you can tell yourself not to do it and you won’t. This is the reason why it is not contagious. Because if it was contagious, you would not be able to do anything about it. Your subconscious is responsible for making you yawn. Yawning is not used to give you more oxygen. (Jerry Yee, M.D., Department of Medicine, UTHSCSA)
Darnit, caught again.
No. The turtles are talking about you in sign language. When they notice you looking, the scurry away.
I’m going to give you a homework assignment. Look up the answer to your question and report back here with the answer you have researched.
Cecil’s column, "Why are yawns contagious?"He doesn’t actually attempt to explain what yawning is caused by, however.
Damn! Wood Thrush beat me to it. Anyway, Alessan, I’m not sure the oxygen hypothesis is still widely accepted. If yawning were an involuntary response to low oxygen levels, we would expect to see yawning in all cases of hypoxia: carbon monoxide poisoning, drowning, emphysema, etc. We don’t. If it were an involuntary response to fatigue, on the other hand, we should yawn all night long. Also, humans tend to yawn most in the hour right after we wake up, and less often before we go to sleep.
The Surfactant Theory goes like this: yawning causes us to stretch our lungs to capacity, which causes the surfactant to be more evenly distributed. Apparently, every animal that uses surfactant for oxygen/CO[sub]2[/sub] exchange also yawns.
The Nolman Valve Theory proposes that yawning “cleans the brain.” We know that yawning increases intracranial pressure. The idea is that this pressure accelerates the drainage of cerebrospinal fluid, thereby causing the ventricles in the brain to make new CSF. This theory seems to be supported by observations that certain brain tumors cause pathological yawning, while people with schizophrenia—whose ventricles are larger than normal—yawn very little. Some people speculate that the reason our eyes get watery when we yawn is because CSF is forced into our tear ducts.
I think that all this is really just a more interesting way of saying, “We really don’t know yet.”
Everytime I hit the back button it reposted the message.
Help, manhattan!
[Moderator’s note: I deleted the dupes. When someone else posts to this thread, I’ll delete this message, too. I can’t delete it now because seriously weird things happen when I delete the last post in a thread. I’d hate to be responsible for the end of the universe just because I think our members deserve clean threads. -manhattan]
[Edited by manhattan on 07-16-2000 at 07:37 PM]
(You’re welcome, Manny.)
Of course, once he deletes Wood Thrush’s message, yours will make no sense, and so he’ll have to delete it too.
The Ryan: That was the whole point. 
Back to the original question: yawning.
Yawning is also exhibited by diabetics in hyperglycaemia and keto-acidosis, so there has to be more to it than just oxygen “hunger”.