We most associate yawning with boredom or being sleepy, but new research suggests it can be good for your health—by cooling down your brain.

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

During winter, Professor Andrew Gallup and his team asked 80 random pedestrians to look at images of people yawning and then recorded whether they yawned in response. They then performed the same trial in the summer.

The researchers found that half of the participants yawned in winter while only a quarter yawned in summer. You may think people would tend 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. This system therefore wouldn't work on a scorching summer's day.

Professor Gallup said: "Yawning should be suppressed—in ambient temperatures exceeding body temperature because taking a deep inhalation of air would not promote cooling.

He also suggested that this is the first study to show that yawning frequency varies from season to season. It could help explain why humans become confused and disorientated in extreme heat as the brain has limited ways of cooling itself down.

The research is published in the journal Frontiers in Evolutionary Neuroscience.

據英國《每日郵報》9月20日報道，人們把多把打哈欠和無聊與瞌睡聯系在一起，但一項新研究表明，打哈欠可以給人腦“降溫”，有益健康。

普林斯頓大學的科學家發現，打一個大大哈欠可以調節人腦溫度，避免人腦過熱。

安德魯•蓋洛普教授和他的團隊在冬天隨機測試了80名路人，讓他們看關于人們打哈欠的圖像，記錄他們是否以打哈欠回應，他們在夏天也做了相同的試驗。

研究人員發現，在冬天，一半參與者都會打哈欠，而在夏天打哈欠的受試者只有25%。也許人們會認為，人在夏天時更傾向于給腦子降溫，但是，根據該理論，打哈欠得通過和較冷的空氣進行熱傳導才能降低人腦溫度。因此，該系統無法在悶熱的夏天發揮作用。

蓋洛普教授說：“當周圍溫度超過人體溫度時，深吸空氣并不能幫助降溫，打哈欠也就會受到抑制。”

他還表示，該研究首次表明，打哈欠的頻率會根據季節而變化，這能夠幫助人們解釋人腦降溫途徑受限時，會變得困惑和茫然的原因。

該研究發表在《進化神經系統前沿》雜志上。