Why Do We Yawn

Why Do We Yawn

2017-10-05    01'35''

主播: Ada^^

183 0

介绍:
Bears yawn. Camels yawn. Most mammals yawn. Why do we yawn? No one really knows the answer. We do know that everyone yawns in the same way. First you open your mouth slowly. Your mouth stays open for about five seconds. Then you quickly close your mouth. We also know that, yawning is contagious or catching. When you see someone yawn, you yawn,too. Many people say that they yawn because they are very bored, or tired. This might be true. However we know that people also yawn, when they are excited or nervous, Olympic runners, for example, often yawn before a race. Why is that? Some scientists believe that yawning makes you more alert, when you yawn, you breathe more deeply. You also stretch the muscle in your face and your neck. Maybe this makes you feel more alert. Scientists do not spend time studying yawning, that is probably because yawning does not hurt. It is just something we do.
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