他伸了伸懒腰，打了个哈欠。
她打了个哈欠，伸了个懒腰。
她打了个哈欠，又刻意地看了看手表。
她并未试图忍住一个哈欠。
他打了个哈欠，伸了伸腰。
他站起身来，伸了个懒腰，打了个哈欠。
她又忍住了哈欠，竭力显出感兴趣的样子。
他张扬地打了个哈欠。
她困得打着哈欠。
他打着哈欠，揉着眼睛，喊道。
罗莎娜强忍住没打哈欠。
微笑、皱眉、挑眉、打哈欠和冷笑都传达信息。
A smile, frown, raised an eyebrow, yawn, and sneer all convey information.
换言之，如果没有令人惊讶之处，它只不过是个哈欠。
In other words, if there are no surprises, it's just a yawn.
你可以给一个因饥饿而打哈欠的可怜孩子一个便士吗？
Will you be kind enough to give a penny to a poor boy who is yawning from hunger?
打哈欠可能通过周期性地降低肺部的压力来帮助清理肺部。
It might be that yawning helps to clear out the lungs by periodically lowering the pressure in them.
越来越多的研究表明，打哈欠是一种让大脑保持冷静的自然方式。
A growing body of research now shows that yawning is nature's way of keeping our brains cool.
让科学家们感到困惑的一个更大的问题是，我们究竟为什么会打哈欠。
A bigger question puzzling scientists is why we yawn at all.
也许这是打哈欠进化为社交线索的一种暗示——“到我们大家睡觉的时间了”。
That may be a hint that yawn evolved as a social cue—"time for us all to go to bed".
很多实验证据证实了打哈欠的另一个不同的功能，它能让我们做好准备，改变活动状态。
The empirical evidence, such as it is, suggests an altogether different function for yawning—namely, that yawning prepares us for a change in activity level.
疲劳理论的另一个缺陷是，打哈欠并不能像该理论所预测的那样，提高警觉性或生理活跃度。
Another flaw of the tiredness theory is that yawning does not raise alertness or physiological activity, as the theory would predict.
如果工作对你来说太辛苦了，我的孩子，那就好好享受你的哈欠吧，希望它们能给你带来好运！
If the work is too hard for you, my boy, enjoy your yawns and may they bring you luck!
在美国也有类似的情况，当有人提到棒球时，有些人会打哈欠甚至皱眉，你可能就是其中之一。
A similar situation exists in America, where there are those individuals you may be one of them who yawn or even frown when somebody mentions baseball.
在你打哈欠、揉眼睛、准备打盹之前，想一想生活在一个瞌睡虫遍地的国家是怎样的一个情况吧。
Before you yawn, rub your eyes and hit the snooze button, consider the consequences of living in a nation of sleepheads.
另一项实验表明，体育运动——尤其是剧烈的运动——可以使呼吸频率增加一倍，但这对打哈欠的频率没有影响。
Another experiment demonstrated that physical exercise, which was sufficiently vigorous to double the rate of breathing, had no effect on the frequency of yawning.
对于打哈欠是由血液中的氧气减少或血液中的二氧化碳增加引起的这种观点，一些实验也同样提出了严重的质疑。
Experiments have also cast serious doubt on the belief that yawning is triggered by a drop in blood oxygen or a rise in blood carbon dioxide.
这与坊间流传的证据相符，即人们常会在既不累也不无聊的情况下打哈欠，只是为即将到来的精神和身体活动做准备。
This accords with anecdotal evidence that people often yawn in situations where they are neither tired nor bored, but are preparing for impending mental and physical activity.
当志愿者在正常的空气中、纯氧的环境下，或者混有超过正常的二氧化碳含量的空气中呼吸时，他们被要求要想着打哈欠。
Volunteers were told to think about yawning, while they breathed either normal air, pure oxygen, or an air mixture with an above-normal level of carbon dioxide.
当志愿者在正常的空气中、纯氧的环境下，或者混有超过正常的二氧化碳含量的空气中呼吸时，他们被要求要想着打哈欠。
Volunteers were told to think about yawning while they breathed either normal air, pure oxygen, or an air mixture with an above-normal level of carbon dioxide.
她打哈欠是对我打哈欠的条件反射。
然而，打哈欠与睡眠模式没有关系。
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