閱讀難度：

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. （點擊《每日郵報》查看原文）

打哈欠可為大腦降溫

???????普林斯頓大學(xué)的科學(xué)家發(fā)現(xiàn)，打一個大大的哈欠可以調(diào)節(jié)大腦的溫度，防止其過熱。

???????據(jù)英國《每日郵報》報道，研究顯示，有一半的研究對象在冬天打哈欠，在夏天打哈欠的僅有四分之一。

???????由此我們推斷出打哈欠可以使大腦降溫。乍一看這似乎與直覺相悖，人們肯定都想在夏天通過打哈欠來幫大腦降溫吧。

???????但從理論上來講，只有通過與吸入的冷空氣進行熱量交換，打哈欠才能為大腦降溫。所以在酷熱的夏日，這套降溫機制根本行不通。

???????另外，由于大腦自己降溫的方式有限，這也就能解釋為什么高溫會使人變糊涂了。

(China.org.cn October 10, 2011)