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Scientists at Princeton University found a big yawn can regulate the temperature of the brain and prevent over-heating, Daily Mail reported.

The researchers found that half of the study participants yawned in winter while only a quarter yawned in summer.

From this they reasoned that yawning cools the brain, which at first seems counter-intuitive. Surely you would want to cool the brain by yawning more in summer?

But according to the theory, yawning cools the brain via a heat exchange with cooler air drawn in during the process. This system therefore wouldn't work on a scorching summer's day.

It could help explain why humans become confused and in extreme heat as the brain has limited ways of cooling itself down. （点击《每日邮报》查看原文）

打哈欠可为大脑降温

       普林斯顿大学的科学家发现，打一个大大的哈欠可以调节大脑的温度，防止其过热。

       据英国《每日邮报》报道，研究显示，有一半的研究对象在冬天打哈欠，在夏天打哈欠的仅有四分之一。

       由此我们推断出打哈欠可以使大脑降温。乍一看这似乎与直觉相悖，人们肯定都想在夏天通过打哈欠来帮大脑降温吧。

       但从理论上来讲，只有通过与吸入的冷空气进行热量交换，打哈欠才能为大脑降温。所以在酷热的夏日，这套降温机制根本行不通。

       另外，由于大脑自己降温的方式有限，这也就能解释为什么高温会使人变糊涂了。

(China.org.cn October 10, 2011)