At least that's what a new study says. Researchers at the University of Vienna found that the

至少這是新的研究上面所說的。Vienna的大學研究員發現

amount of yawning we do increases when our brains are hot. (Via ScienceDirect)

當我們的頭腦過載，打哈欠的頻率的確就會增加

"Much like a computer, your brain works best at a certain temperature and tries to avoid

跟電腦很像，你的大腦在一定的溫度下有最佳的效能，並且試著避免

over-heating. And it turns out, yawning increases your heart rate, blood flow and the use of

過熱。然後這種運作方式，打哈欠會加速心跳、血液流動的速度，還有你

muscles in your face, which are all essential to cooling the brain." (Via YouTube / AsapSCIENCE

臉部肌肉的使用也會受影響。所以大腦的降溫變得很重要。

)

So, why is yawning associated with being tired? Well, exhaustion and sleep deprivation are

所以，為什麼打哈欠跟疲倦扯上關係呢？疲倦以及失眠被

known to increase overall brain temperature. (Via Flickr / twob / nate2009)

認為是增加大腦溫度的原因。

But as the Daily Mail points out, researchers found people yawn less when it's hotter than

但是，就如同『每日郵報』指出，研究人員發現，當大腦的溫度高於正常體溫時，

normal body temperature outside, which makes sense — you would be breathing in hot air.

人們比較少打哈欠。這也說得通，因為你被迫在很熱的環境呼吸。

Not exactly cooling.

跟降溫沒什麼關係

The research says people also yawn less at the other extreme. When it's super cold outside

研究員指出，人們在極端的狀態下較少打哈欠。當外面天氣超冷

— like, say, frozen — brain cooling may not be necessary. (Via Walt Disney Studios

像是下雪，大腦的降溫變得沒這麼重要。

/ "Frozen")

Time notes this study builds on research that showed yawns are preceded by sporadic rises

『時代雜誌』紀錄著這個研究，調查顯示打哈欠可以藉由

in brain temperatures and are followed immediately by decreases in brain temps.

大腦溫度提升被事先偵測到，也可以藉由大腦溫度的下降被追蹤。

We still don't know why yawning is contagious, but the researchers argue it might be an evolutionary

我們尚未找出打哈欠會傳染的主因，但是研究員證明它有可能是一個特徵的演化，

trait to improve overall alertness.

為了只是要提升整體的警覺。

TED says it's an empathetic response.

TED 說這是一個移情的反應

"In fact, contagious yawning starts occurring when we are about 4 or 5 years old, at the

「其實，打哈欠會傳染早在我們四五歲時就已經發生啦，

point when children develop the ability to identify other emotions properly."

這時小孩正在發展辨識其他情緒的能力

And now I'll be yawning all day.

現在，我今天一整天都會打哈欠啦！！！