According to research, people are more likely to yawn at higher temperatures. When they yawn, the act of stretching their jaws sends more blood to their brain, which can help keep it cool. Also, taking in a big breath of air during a yawn ensures a minor increase in blood flow to the brain. Another theory proposes that yawning is a survival mechanism that increases people’s level of alertness. If someone is getting drowsy and their awareness begins to decrease, yawning may be triggered to keep them from falling asleep.
根据研究，人们在高温下较有可能打哈欠。当他们打哈欠，伸展下巴的动作会让更多血液流向大脑，这可以帮助它保持冷却。此外，打哈欠时吸进大口空气能确保输往大脑的血流略为增加。另一项理论指出打哈欠是增加人们警觉性的生存机制。如果某人变得昏昏欲睡且意识开始消退，打哈欠或许会被启动来防止其睡著。
生活必备字词：
yawn n. & vi.（打）哈欠
drowsy a. 昏昏欲睡的
keep... from V-ing 使……免于……
◆免费线上听外师朗读 https://ivyforfree.pse.is/3jks97
本文节录自《常春藤生活英语》杂志，完整内容请见七月号。
點擊閱讀下一則新聞
