科學界最令人困惑問題之一 我們爲什麼會打哈欠2

Many theories have instead focussed on thestrange, contagious nature of yawning – a fact that I know only too well frommy conversation with Provine. “Around 50% of people who observe a yawn willyawn in response,” he says. “It is so contagious that anything associated withit will trigger one… seeing or hearing another person, or even reading aboutyawning.” For this reason, some researchers have wondered if yawning might be aprimitive form of communication – if so, what information is it transmitting? We often feel tired when we yawn, so one idea is that it helps set everyone’sbiological clocks to the same rhythm. “In my view the most likely signallingrole of yawning is to help to synchronize the behaviour of a social group – tomake them go to sleep more or less at the same time,”saysChristian Hess, at the University of Bern in Switzerland. With the sameroutine, a group can then work together more efficiently throughout the day.

其他很多理論都將關注點集中於打哈欠那奇怪的、具有傳染性的本質特點上——這一本質在我和普羅文的談話中我已經得到了很好的體會。“在觀察哈欠行爲的人之中，大約有50%的人也會同時打哈欠，”普羅文說，“打哈欠行爲的傳染力如此之大，以致所有與其相關的事物都會引起另一個哈欠......不論是看到還是聽到另外一個人打哈欠，或甚至是閱讀有關哈欠的內容。”基於這個原因，一些研究者在想打哈欠可不可能是溝通交流的一種原始形式？如果是的話，打哈欠這種形式又是在傳遞怎樣的信息呢？我們在打哈欠的時候常常會感到疲憊，所以有人認爲打哈欠是爲了幫助將每個人的生物鐘調整到同樣的節奏。“在我看來，打哈欠最有可能的信號作用是幫助同步化一個社會羣體的行爲，從而使得他們在同一時間裏調整睡眠時間，”瑞士伯爾尼大學的克利斯汀·赫斯這樣說。有了同樣的生活節奏後，一個團隊就能夠在一天裏更有效地工作。

Yet we also yawn during times of stress:Olympic athletes often do it before a race, while musicians sometimes succumbbefore a concert. So some researchers, including Provine, believe that thestrenuous movements might have a more general role in rebooting the brain –when you are sleepy they make you more alert, or when you are distracted theymake you more focussed. Spreading through a group, contagious yawns could thenhelp everyone reach the same level of attention, making them more vigilant to athreat, for instance. The mechanism is somewhat hazy –though oneFrench researcher, Olivier Walusinski, proposes that yawning helps to pumpcerebrospinal fluid around the brain, which could trigger a shift in neuralactivity.

我們在壓力大的時候也會打哈欠：參加奧運會的運動員們經常會在比賽開始前打哈欠，音樂家在音樂會前有時也會這樣。因此包括普羅文在內的一些研究者相信打哈欠這一費力的行爲可能有着重新激活大腦的作用——當你睏倦的時候打哈欠能夠讓你變得更加警覺，或者當你有所分心的時候它會讓你集中注意力。比如，通過在一個羣體裏的擴散，感染性的哈欠能夠幫助每一個人獲得同樣程度的注意力，從而使得他們對於威脅更加警惕。這一機制仍是不確定的，儘管有一位名叫奧利維耶·瓦盧辛斯基（Olivier Walusinski）的法國研究者提出打哈欠有助於促進大腦周圍腦脊液的分泌，而這種液體能夠引起神經活動的變化。

With so many competing and contradictoryideas, a grand unifying theory of yawning may seem like a distant speck on thehorizon. But over the last few years, one underlying mechanism has emerged thatcould, potentially, appease all these apparent paradoxes in one fell ew Gallup, now at the State University of New York at Oneonta, was firstinspired with the idea during his undergraduate degree, when he realised thatyawning might help to chill the brain and stop it overheating. The violentmovement of the jaws moves blood flow around the skull, he argued, helping tocarry away excess heat, while the deep inhalation brings cool air into thesinus cavities and around the carotid artery leading back into the ’s more, the strenuous movements could also flex the membranes of sinuses –fanning asoft breeze through the cavities that should cause our mucus to evaporate,which should chill the head like air conditioning.

有這麼多不同的觀點相互競爭，要找到一個統一的哈欠理論的可能性非常小，小得就像視野裏遠處的微塵。但在最近的幾年裏，出現了一個相關理論，它擁有一次性化解所有這些互相矛盾觀點的潛力。安德魯·蓋勒普來自奧尼昂塔紐約州州立大學，他最初萌生這一想法還是在他攻讀學士學位期間，在那時候安德魯·蓋勒普意識到打哈欠可能具有冷卻大腦，防止大腦升溫過度的作用。他認爲打哈欠過程中頜的大幅度運動促進了血液在頭骨周圍的流動，從而帶走了過度的熱量，同時打哈欠過程的深吸氣又將較低溫的空氣帶入了竇穴和頸動脈周圍，頸動脈又將冷卻後的血液輸回大腦。此外，打哈欠這一大幅度動作還能夠活動鼻竇的細胞膜，從而經竇穴引起較小的氣流波動，這一波動會使得我們的粘液汽化，從而達到冷卻大腦的作用，效果就像空調一樣。

The most obvious test was to see if peopleare more or less likely to yawn in different temperatures. In normalconditions, Gallup found that around 48% felt the urge to yawn, but when heasked them to hold a cold compress to their foreheads, just 9% thing through the nose, which could also cool the brain, was even moreeffective, completely dampening his subjects’urge to yawn –potentiallysuggesting a handy trick for anyone facing embarrassment during a tediousconversation.

最明顯的測試就是去看人們在不同的溫度下是否會改變打哈欠的頻率。在正常條件下，蓋勒普發現大約有48%的人會感覺到打哈欠的衝動，但是當他讓他們將一塊冷的敷布壓在額頭上時，這一數字減到了9%。通過鼻子呼吸也可以冷卻大腦，這一方式來得更爲有效，可以完完全全抑制住打哈欠的衝動。對於任何置身於冗長無聊的對話，但又想避免打哈欠的尷尬的人來說，這是一個很好的應對辦法。