打哈欠真的会传染吗？

 人们常说打哈欠会传染，每次你一打呵欠，周围的人也会跟着打哈欠。难道哈欠真的可以传染，还是仅仅是巧合而已？我们来看看神经学家是怎么说的吧！

"A yawn is an instinctive¹ behavior: You don't have to learn to do it, and yawns are even present before birth." says Robert Provine, a professor of psychology² and neuroscience at the University of Maryland, Baltimore County.

When we see someone else yawn, we don't think to ourselves, "Well, I'll yawn, too." It just happens -- it's instinctive, and it's a very primal³ aspect of human behavior that goes back to ancient herd⁴ mentality⁵.

Adelie penguins⁶, for instance, employ yawning as part of their courtship ritual. The happy couples face off amid the ice floes and the males engage in what is described as an "ecstatic display," their beaks⁷ open wide and their faces pointed⁸ skyward.

It may be, therefore, that when your entry upon the scene inspires a round of uncontrollable yawning, you have merely stumbled onto a gaggle of Adelie penguins in disguise, who are signaling their powerful erotic longing⁹ for you. A slim hope, admittedly, but any port in a storm.

As for the larger question of why yawns are catching¹⁰, nobody really knows. Fact is, we don't know why people yawn.

It was long believed you yawned when there was too much carbon dioxide and not enough oxygen in your blood. A part of your brain called the brain stem detected this and triggered the yawn reflex. Your mouth stretched wide and you inhaled¹¹ deeply, shooting a jolt¹² of oxygen into the lungs and thence to the bloodstream.

Subsequently, you exhaled¹³ a lot of CO2. Often you'd stretch while yawning, which seemed to temporarily improve circulation. You yawned and stretched a lot more when you got tired because your breathing slowed down.

Or so people thought. In recent years, though, a few radicals¹⁴ have said the preceding is all malarkey. Who knows, they say, maybe we yawn because it's too warm in the room.

Cecil isn't about to settle the issue here, and he doesn't need to. We merely observe that whatever yawn-inducing conditions prevail for you also apply to your friends.

If you're out late in some crowded dive, you're probably all tired, all warm under the collar, and all breathing the same stale air. You're probably all on the verge¹⁵ of a yawn, too, and the power of suggestion from seeing one person do it is enough to push everybody else over the edge.

Adults rarely catch a case of the yawns from a child or animal, which tends to corroborate¹⁶ this idea.

Children usually have different sleep schedules and respiration¹⁷ rates from adults, so you would expect them to yawn at different times. Animals, on the other hand, often yawn not for physiological¹⁸ reasons but as a display of hostility¹⁹, to which humans are evidently unresponsive.

1 instinctive   

adj.(出于)本能的；直觉的；(出于)天性的

参考例句：

• He tried to conceal his instinctive revulsion at the idea.他试图饰盖自己对这一想法本能的厌恶。
• Animals have an instinctive fear of fire.动物本能地怕火。

2 psychology   

n.心理，心理学，心理状态

参考例句：

• She has a background in child psychology.她受过儿童心理学的教育。
• He studied philosophy and psychology at Cambridge.他在剑桥大学学习哲学和心理学。

3 primal   

adj.原始的；最重要的

参考例句：

• Jealousy is a primal emotion.嫉妒是最原始的情感。
• Money was a primal necessity to them.对于他们，钱是主要的需要。

4 herd   

n.兽群，牧群；vt.使集中，把…赶在一起

参考例句：

• She drove the herd of cattle through the wilderness.她赶着牛群穿过荒野。
• He had no opinions of his own but simply follow the herd.他从无主见，只是人云亦云。

5 mentality   

n.心理，思想，脑力

参考例句：

• He has many years'experience of the criminal mentality.他研究犯罪心理有多年经验。
• Running a business requires a very different mentality from being a salaried employee.经营企业所要求具备的心态和上班族的心态截然不同。

6 penguins   

n.企鹅( penguin的名词复数 )

参考例句：

• Why can penguins live in cold environment? 为什么企鹅能生活在寒冷的环境中？ 来自《简明英汉词典》
• Whales, seals, penguins, and turtles have flippers. 鲸、海豹，企鹅和海龟均有鳍形肢。 来自《现代英汉综合大词典》

7 beaks   

n.鸟嘴( beak的名词复数 )；鹰钩嘴；尖鼻子；掌权者

参考例句：

• Baby cockatoos will have black eyes and soft, almost flexible beaks. 雏鸟凤头鹦鹉黑色的眼睛是柔和的，嘴几乎是灵活的。 来自互联网
• Squid beaks are often found in the stomachs of sperm whales. 经常能在抹香鲸的胃里发现鱿鱼的嘴。 来自互联网

8 pointed   

adj.尖的，直截了当的

参考例句：

• He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。
• She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。

9 longing   

n.（for）渴望

参考例句：

• Hearing the tune again sent waves of longing through her.再次听到那首曲子使她胸中充满了渴望。
• His heart burned with longing for revenge.他心中燃烧着急欲复仇的怒火。

10 catching   

adj.易传染的，有魅力的，迷人的，接住

参考例句：

• There are those who think eczema is catching.有人就是认为湿疹会传染。
• Enthusiasm is very catching.热情非常富有感染力。

11 inhaled   

v.吸入( inhale的过去式和过去分词 )

参考例句：

• She closed her eyes and inhaled deeply. 她合上双眼，深深吸了一口气。
• Janet inhaled sharply when she saw him. 珍妮特看到他时猛地吸了口气。 来自《简明英汉词典》

12 jolt   

v.（使）摇动，（使）震动，（使）颠簸

参考例句：

• We were worried that one tiny jolt could worsen her injuries.我们担心稍微颠簸一下就可能会使她的伤势恶化。
• They were working frantically in the fear that an aftershock would jolt the house again.他们拼命地干着，担心余震可能会使房子再次受到震动。

13 exhaled   

v.呼出，发散出( exhale的过去式和过去分词 )；吐出（肺中的空气、烟等），呼气

参考例句：

• He sat back and exhaled deeply. 他仰坐着深深地呼气。
• He stamped his feet and exhaled a long, white breath. 跺了跺脚，他吐了口长气，很长很白。 来自汉英文学 - 骆驼祥子

14 radicals   

n.激进分子( radical的名词复数 )；根基；基本原理；[数学]根数

参考例句：

• Some militant leaders want to merge with white radicals. 一些好斗的领导人要和白人中的激进派联合。 来自《简明英汉词典》
• The worry is that the radicals will grow more intransigent. 现在人们担忧激进分子会变得更加不妥协。 来自辞典例句

15 verge   

n.边，边缘；v.接近，濒临

参考例句：

• The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
• She was on the verge of bursting into tears.她快要哭出来了。

16 corroborate   

v.支持，证实，确定

参考例句：

• He looked at me anxiously,as if he hoped I'd corroborate this.他神色不安地看着我，仿佛他希望我证实地的话。
• It appeared that what he said went to corroborate my account.看来他所说的和我叙述的相符。

17 respiration   

n.呼吸作用；一次呼吸；植物光合作用

参考例句：

• They tried artificial respiration but it was of no avail.他们试做人工呼吸，可是无效。
• They made frequent checks on his respiration,pulse and blood.他们经常检查他的呼吸、脉搏和血液。

18 physiological   

adj.生理学的，生理学上的

参考例句：

• He bought a physiological book.他买了一本生理学方面的书。
• Every individual has a physiological requirement for each nutrient.每个人对每种营养成分都有一种生理上的需要。

19 hostility   

n.敌对，敌意；抵制［pl.］交战，战争

参考例句：

• There is open hostility between the two leaders.两位领导人表现出公开的敌意。
• His hostility to your plan is well known.他对你的计划所持的敌意是众所周知的。