关于开头是what is a yawn and why do people yawn?英语短文

关于开头是what is a yawn and why do people yawn?英语短文

When we yawn, we inhale air, and stretch our eardrums, and that is why our ears 'pop' when we yawn. There is a very common misconception about yawning, and that is people yawn when they need more air. But according to research studies, this is not true. Take excercising for an example. When we excerscie, we naturally need to inhale more oxygen, however, we do not yawn more during excercise.
A most likely explanation for why one yawns, is because one needs to cool off one's brain. Our brains require very specific temperatures to operate well, and when we are feeling tired exhausted, our brain temperatures increase, triggering an instict to yawn, and cool off the brain. The intake of air cools the facial blood, hence helping to cool off our brain too.

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What is a yawn(哈欠) and why do people yawn? A yawn is often associated with a person being tired. But this is not always the cause for a yawn.But this is not always the cause for a yawn. People yawn for many reasons including stress, boredom, emotion and overwork. Have you noticed that yawning seems to be contagious (会传染的)? If one person yawns, this appears to cause another person to yawn. Researchers have found that 40-60% of people who see a picture of someone yawning will yawn themselves. Even reading the word YAWN can make people yawn.Some people think that yawning is rude and suggests that you are bored or uninterested. Maybe a yawn is a signal to a group that it’s time to go to sleep, or if someone yawns when they're bored, it may be a sign to change the topic of conversation. Yawning is not limited to humans. Animals of all types yawn. If you have a dog or cat, you've probably seen your pet yawn several times. Even some birds yawn such as cockatiel parrots, Adelie penguins and Emperor penguins. Some of the scientific explanations of why we yawn claim it is caused by physical needs. One likely explana¬tion is that the yawning reflex happens when our blood needs more oxygen. The deep breath helps supply the levels of oxygen in our blood. Another common theory is that a yawn helps regulate our body temperature. It is also thought that the same chemicals in our brain that affect our moods and emotions cause us to yawn. Superstitions about yawning have been around for hundreds of years and can date back to the ancient Greeks. A common superstition says that a person must cover his or her mouth when yawning so that the soul does not escape through the mouth. Other people believe that yawning is a sign that danger is near. Today most people do not believe these superstitions and know that a yawn is a physical reflex. Did you yawn while reading this article?

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