生物谷報(bào)道：哈欠人人打，但可能很少有人留意到打哈欠后會(huì)感覺(jué)頭腦更冷靜、注意力更集中。不信,？你現(xiàn)在就可以打個(gè)哈欠試試。
美國(guó)紐約州立大學(xué)的心理學(xué)家在最新一期《新科學(xué)家》雜志上報(bào)告說(shuō),，研究顯示,，打哈欠可促進(jìn)血液流動(dòng)，“冷卻”大腦，提高大腦靈敏度,。這一研究結(jié)果也可以解釋為什么打哈欠會(huì)“傳染”,。心理學(xué)家說(shuō)，打哈欠“傳染”是移情機(jī)制發(fā)揮作用,，有助于提高群體注意力,。
科學(xué)家征募了４４名大學(xué)生，讓他們分別單獨(dú)觀(guān)看人們打哈欠的影片,，并記錄每名志愿者“傳染性”打哈欠的次數(shù),。學(xué)生們被要求以下列４種方式之一呼吸：完全用口呼吸、完全用鼻呼吸,、戴上鼻塞用口呼吸或正常呼吸,。
科學(xué)家發(fā)現(xiàn)，觀(guān)看別人打哈欠時(shí),，那些被要求正常呼吸或用口呼吸的人有一半打哈欠；而被要求用鼻呼吸的人沒(méi)有一個(gè)打哈欠,?？茖W(xué)家還發(fā)現(xiàn)，那些前額上放一個(gè)冷敷包的人沒(méi)有因觀(guān)看影片而“傳染”上打哈欠,，而那些前額上放熱敷包的人則受到“傳染”而打上了哈欠,。
科學(xué)家由此認(rèn)為，打哈欠能夠“冷卻”大腦,。參與這項(xiàng)研究的戈登·蓋洛普解釋說(shuō),，鼻腔中的血管可以向大腦輸送溫度較低的血，因此通過(guò)鼻呼吸或冷卻前額,，能夠起到與打哈欠類(lèi)似的效果,，使得人們沒(méi)有必要再打哈欠。而除此之外的許多人都打上了哈欠,，則反過(guò)來(lái)證實(shí)了打哈欠具有“冷卻”大腦的功效,。他推測(cè)說(shuō)，大腦在“冷卻”狀態(tài)時(shí)工作效率會(huì)更高,，因此打哈欠也許有助于提高大腦靈敏度和增強(qiáng)大腦功能,。（引自新華網(wǎng)）
原始出處：
Yawning may boost brain's alertness
02 July 2007 NewScientist.com news service
Rowan Hooper
Yawning is not something we usually aim to provoke among our readers, but have a yawn now. Does your brain feel cooler? Do you feel more attentive? According to psychologists Andrew Gallup and Gordon Gallup of the State University of New York at Albany, that is why we yawn: to boost blood flow and chill the brain.
Not only that, brain-cooling explains why you can "catch" a yawn, says Gordon Gallup. "We think contagious yawning is triggered by empathic mechanisms which function to maintain group vigilance." In other words, yawn-catching evolved to help raise the attentiveness of the whole group.
The pair recruited 44 college students to watch, individually, films of people yawning and recorded the number of contagious yawns each volunteer made. Students were told to inhale and exhale in one of four ways: strictly orally; strictly nasally; orally while wearing a nose plug; or just breathe normally.
Fifty per cent of people told to breathe normally or through their mouths yawned while watching other people yawn, while none of those told to breathe through their noses yawned. The researchers also found that subjects who held a cold pack to their forehead did not catch yawns from the film, while those who held a warm or room-temperature pack yawned normally (Evolutionary Psychology, vol 5, p 92).
Blood vessels in the nasal cavity send cool blood to the brain, so breathing through the nose or cooling the forehead cools the brain and eliminates the need to yawn, says Gordon Gallup. He argues that brains operate more efficiently when cool, and that yawning enhances brain function. "According to our hypothesis, rather than promoting sleep, yawning should antagonise sleep," he says.
"Paratroopers report yawning before they jump," says Robert Provine of the University of Maryland, Baltimore County. "Yawning signals a transition between the behavioural states of wakefulness and sleepiness, and boredom to alertness."
From issue 2610 of New Scientist magazine, 02 July 2007, page 14
