Explained. It’s for thermal management of the brain.
I don’t buy it. A more natural and effective mechanism for cooling the brain would be to sweat. It seems to me that the real reason is to increase oxygenation of the blood for a short period of time which in turn somehow increases alertness. The study indicates that people yawn most often when they are tired or waking up. But those are times when the person needs to be alert.
Here’s some more observations. People don’t yawn when they are asleep. There seems to be some evidence that breathing pure oxygen (for brief periods) helps make a person more alert for a period of time. It’s to the point where we have oxygen bars and canned oxygen.
That is odd, I remember reading about this on sciencedaily.com a few years ago. I guess they did more research since then to confirm the results and earn a report on discovery.com
Since I’ve read that a ways back I’ve since noticed how often people contagiously yawn now. And I’ve also noticed how often when people do yawn in groups, someone always remarks, “Stop it, your making me yawn…Why is that?”. I find myself often explaining why and people find it quite interesting.
Karl, I think you might want to rethink your conclusion. After all, haven’t you ever heard of a “brain freeze” from eating an Icee or ice cream too fast? There are nerve endings that drop straight down from the base of the brain and line the roof of your mouth. When the nerve endings get overwhelmed by the coldness in the ICEE they send signals to the brain that make it think it is in danger of getting too cold. So, the brain fires off pain receptors to get your conscious decision making to respond and do something about it. One way to remedy this is to press your tongue, which is full of warm blood, hard up against the roof of your mouth and give the nerve endings a warm signal to interpret and in turn shutdown the pain receptors.
The point of all this, is to show how sensitive the brain is to the temperatures sensed by the nerve endings in the roof of your mouth. Putting something extremely cold in your mouth almost makes your eyes pop open and wake you up. On the other end, a warm cup of tea or a bowl of chicken soup can soothe you and calm you down.
Yes, we as humans have evolved the ability to sweat in order to exchange heat. We also expel quite a bit of heat through our respirations as well. In fact, not that many animals have the ability to sweat. Most animals exchange heat through respirations and through the blood vessels that line the ears, nose, and throat. Think about a dog for a second; they yawn all the time.
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