Do u believe it? Bill Nye's answer about why we yawn!?

Question

I find this interesting. I always thought we yawned to get more oxygen to the brain. Do you agree that it is to let others know we are tired so that we all sleep at the same time and get up at the same time? This may be for safety reasons back when we lived in the wild?

Hi Bill,
Why do we yawn? And why does it seem contagious?
--Sleepy Ruminator

Dear Sleepy Ruminator,
Of course, yawning seems to be a very old form of behavior. It seems to be programmed deep in our brains. I've seen dogs yawn, and it makes me want to yawn right along with 'em. When your best canine friend is opening his jaws wide and shaking his shoulders, you can bet that he's not anxious to go outside and play or go for a long old walk. Modern wild dogs in Africa live in packs. They seldom stray off on their own. A yawn is a dog's way of telling her buddies in the dog pack (or you as her keeper) that she's ready for some doggie z's.
Here is the link for the whole excerpt:
http://encarta.msn.com/encnet/feature

Answer 1

That is pretty interesting. I've never heard that particular explanation before. I think it makes the most sense of all the explanations I've heard.

The hyperlink doesn't work though.

Answer 2

From Wikipedia:

Causes of yawning:
1. An indication of tiredness, stress, over-work, or boredom.
2. An action indicating psychological decompression after a state of high alert.
3. A means of expressing powerful emotions like anger, rejection, apathy, or tedium.

A yawn can express strong anti-social messages, and so in some cultures people try to mute or mask them by placing a concealing hand over the yawning mouth.

A long-standing hypothesis is that yawning is caused by an excess of carbon dioxide and lack of oxygen in the blood. The brain stem detects this and triggers the yawn reflex. The mouth stretches wide and the lungs inhale deeply, bringing oxygen into the lungs and hence to the bloodstream. It is almost certain however, that this hypothesis is not correct. One study documented that this effect does not exist.[2] A more recent hypothesis is that yawning is used for regulation of body temperature. Another hypothesis is that yawns are caused by the same chemicals (neurotransmitters) in the brain that affect emotions, mood, appetite and other phenomena. These chemicals include serotonin, dopamine, glutamic acid and nitric oxide. As more of these compounds are activated in the brain, the frequency of yawning increases. Conversely, a greater presence in the brain of opiate neurotransmitters such as endorphins, reduces the frequency of yawning. Patients taking the serotonin reuptake inhibitor Paxil (Paroxetine HCl) have been observed yawning abnormally often. Another theory is that yawning is similar to stretching. Yawning, like stretching, increases blood pressure and heart rate while also flexing many muscles and joints. It is also theorized that yawning helps redistribute an oil-like substance which coats the lungs and aids breathing. Some have observed that if you try to stifle or prevent a yawn by clenching your jaws shut, the yawn is unsatisfying. As such, the stretching of jaw and face muscles seems to be necessary for a good yawn.

The yawn reflex is often described as contagious: if one person yawns, this will cause another person to "sympathetically" yawn.[3] The reasons for this are unclear; however, recent research suggests that yawning might be a herd instinct.[4] Other theories suggest that the yawn serves to synchronize mood behavior among gregarious animals, similar to the howling of the wolf pack during a full moon. It signals tiredness to other members of the group in order to synchronize sleeping patterns and periods of activity. It can serve as a warning in displaying large, canine teeth. This phenomenon has been observed among various primates. The threat gesture is a way of maintaining order in the primates' social structure. The contagion of yawning is interspecific (i.e., try yawning in front of your dog). Oddly, sometimes sympathetic yawning may be caused by simply looking at a picture of a person or animal yawning, or even seeing the word "yawn".

Answer 3

I agree it is not to get more oxygen, since we actually inhale very little during a yawn. But there is alot of stretching going on in you respiratory system when you yawn. So its really a stretch more than anything. Like a cat: they don't stretch their bodies to communicate (and they often yawn when they stretch).

Answer 4

It never made much sense to me that it was for oxygen. We don't need oxygen when we're sedentary, we need it while exercising. I don't yawn when I'm exercising.

Yawning is also clearly contagious - but need for oxygen certainly isn't!

However, I think all of this is pretty much speculation. There doesn't seem to be a lot of conclusive research on this.

Answer 5

OK, the working link is down below:

As for me, since we are such social animals, I don't see why not. I agree that there is a lot of stretching involved, as noted above, but it is the same kind of relaxing stretching I do when I get ready for bed, too -- snuggly stretches. So, I'd say yes! Makes sense to me.

Answer 6

I don't buy it. I just tell my wife when I'm tired and going to bed.

Answer 7

i always thought it was for more oxygen too! idk and i think it's funny that if you watch someone yawn you yawn too.