她打着呵欠，舒适地转身侧向一边。
她伸开手臂，打了个大呵欠。
克鲁克的眼睑垂了下来，打起了呵欠。
他敞开睡衣站着打呵欠。
他装着打了一个呵欠。
她忍住了呵欠。
打呵欠会分散注意力，消耗精力，耗费时间。
他已经很多个小时没吃东西了，饿得开始打呵欠。
It was many hours since he had eaten anything and he started to yawn from hunger.
两个人随即打了个呵欠，印第安·乔说：“我困得要死了！”
Both men presently fell to yawning, and Injun Joe said: "I'm dead for sleep!"
希德打了个呵欠，伸了个懒腰，然后用胳膊肘支起身子，哼了一声，开始瞪着汤姆。
Sid yawned, stretched, then brought himself up on his elbow with a snort, and began to stare at Tom.
另一种完全不同的理论认为，打呵欠有助于生命早期肺部的生理发育，但对成年人没有任何剩余的生理功能。
A completely different theory holds that yawning assists in the physical development of the lungs early in life, but has no remaining biological function in adults.
打呵欠最关键的诱因就是大脑的温度。
她张口打呵欠。
主要在早上和中午，老人比年轻人打的呵欠少。
Aged people yawn less than younger ones, mainly during morning and mid-afternoon.
看门人半露出身子，打着呵欠，似醒非醒，手中拿着蜡烛。
The porter half made his appearance yawning, vaguely awake, and with a candle in his hand.
他动弹了一下，然后睁开了眼睛，打了个呵欠，之后对我笑了笑。
He stirred and then opened his eyes. He yawned and then smiled at me.
现在他们明白了呵欠对于鸟类和哺乳类来说起到了散热器的作用。
It's now believed yawning operates like a radiator for birds and mammals.
科学家还猜测有羽毛的恐龙会生虱子，还认定呵欠在黑猩猩中也是会传染的。
Scientists also hypothesized that feathered dinosaurs had lice and determined that yawns are contagious among chimpanzees.
但是这项新的关于呵欠的研究改变了大众对呵欠的看法——只不过是无聊的表现。
But the new study on yawning changes the popular notion that yawns are mere signs of boredom.
工作时呵欠连天不仅仅效率低下，更糟的是，可能会引起严重的生产事故。
Nodding off at work isn't just unproductive; in the worst cases, it can cause serious industrial accidents.
不仅婴儿和新生儿有呵欠行为，就连12 -14周的胎儿也会打呵欠。
It has not only been observed in infants and in newborns, but also in fetuses of 12-14 weeks' gestational age.
这表明打呵欠是因为大脑温度升高所触发的，且“实际上促进了大脑降温”盖洛普说。
This suggests yawns are triggered by an increase in brain temperature and "actually promote brain cooling," Gallup said.
在冬天，当室外平均温度21度时，45%的人看到别人打呵欠的图片时自己也会打哈欠。
In the winter, when outdoor temperatures averaged 21 degrees, 45 per cent of people responded to the images by yawning themselves.
举个例子，呵欠在环境温度超过体温时不大可能发生，因为这时候深吸一口热空气只能帮倒忙。
For instance, yawning should not occur when ambient temperatures exceed body temperature, as taking a deep inhalation of warm air would be counterproductive.
呵欠传染被认为是进化出来用于保持群体的警惕性使群体“在危险面前保持警觉，”盖洛普说。
Contagious yawning is thought to be an evolved mechanism for keeping groups alert so they "remain vigilant against danger," Gallup said.
研究人员发现，在看别人打呵欠的视频时，用鼻子呼吸的人比用口腔呼吸的人打呵欠的几率要小。
The researchers found that those who breathed through the nose rather than the mouth were less likely to yawn when watching a video of other people yawning.
“过多呵欠的症状经常是癫痫病人病情发作的先兆，而且可以预测头痛病人偏头痛的发作，”他补充道。
"Bouts of excessive yawning often precede the onset of seizures in epileptic patients, and predict the onset of headaches in people who suffer from migraines," he added.
但是在夏天，当环境温度远高于人体平均温度37度时，看同样图片而产生打呵欠反应的人还不到四分之一。
But in summer, when conditions are much hotter than the average body temperature of 37 degrees, fewer than a quarter yawned.
打呵欠不仅是疲劳或厌倦的信号——根据科学家的最新发现，它还是人体用来自动调节大脑温度的一种手段。
Yawning is not just a sign of tiredness or boredom - it is the body's method of keeping our brain cool, scientists have found.
另外，在极度寒冷的时候打呵欠也许不大合适，因为这时通常会将冷空气送到大脑，从而使大脑发生热冲击。
In addition, yawning when it is extremely cold may be maladaptive, as this may send unusually cold air to the brain, which may produce a thermal shock.
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