5.Yawning

　　打哈欠

　　Yawning is a puzzling phenomenon. Even the simple act of talking about it is enough to make some people do it (some of you are probably doing it right now). There really is no other bodily function quite like it.

　　打哈欠是一个令人迷惑不解的现象。即使是仅仅谈论一下也足以使一些人打个哈欠（你们中的一些人也许现在正打哈欠呢）。真的没有什么其他的身体机能会像打哈欠一样具有传染性了。

　　Now, some of you reading this may be aware of the long-standing theory that the purpose of yawning is to keep us alert by forcing our bodies to take in an extra large gulp of oxygen. That makes sense, because we mostly yawn when we’re tired or bored, situations where an extra burst of energy would come in handy.

　　此刻，也许你们当中的一些人想到了一个由来已久的理论：打哈欠的目的是通过迫使我们的身体吸入一大口氧气来使我们保持清醒。这么说是有道理的，因为当我们感到疲倦和无聊时，往往都会打哈欠。在这种情况下一股能量会补充进身体，进而振奋我们的精神。

　　The thing is, experiments have conclusively disproven that theory over the years. In fact, there is no universally agreed upon theory for why we actually yawn, even though everyone does it. A commonly accepted theory is that yawning actually cools down the brain, because various experiments have shown that one of the few things to actually change in the body during a yawn is the temperature of the brain itself.

　　可事实是，这些年来，实验已经完全否定了这一理论。实际上，尽管每个人都会打哈欠，可关于我们打哈欠的原因仍没有普遍认同的理论。一种人们广为接受的理论称打哈欠事实上能使大脑的温度下降，因为各种各样的实验已经说明当人打哈欠时，人体为数不多的变化之一就是大脑自身温度的下降。

　　As for why yawning is contagious, no one knows that either.

　　至于打哈欠为什么会传染，也没有人知道原因。

    》》更多精彩冲分课程：
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(责任编辑：田学江)