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Let's say it's getting late, you're studying with a group of friends around a table,
假设现在已经很晚了，你和一群朋友围坐在桌子旁学习，
and you see one of them stretch and yawn.
这时，你看到一个人伸腰打了个哈欠。
You don't feel especially tired, but soon enough, without even realizing it, you yawn too.
你感觉不是特别累，但不久，也不知不觉得打了个哈欠。
Then, the yawn spreads around the table,
然后，哈欠在桌子四周的人群中扩散开来，
with more and more of your friends picking it up unconsciously.
越来越多的朋友开始不自觉得打哈欠。
This sort of contagion can happen with other things, like sniffing or laughter,
这种传染可以发生在其他事情上，比如吸气或大笑，
and it has baffled psychologists for a while.
这让心理学家困惑了一段时间。
Most scientists agree that these so-called echophenomena exist,
大多数科学家都同意所谓的模仿现象存在，
but there are a couple different hypotheses about why they happen.
但是关于它们的起因有几个不同假设。
Several clues come from studies looking at what kinds of animals and people actually catch yawns.
对什么样的动物与人类能传染哈欠的观察研究得出了几条线索。
We've only seen contagious yawning in certain species,
我们只发现传染性哈欠在特定物种中出现，
like humans, chimpanzees, baboons, and in response to us, dogs.
比如人类、 黑猩猩、狒狒以及回应我们的狗。
These are all very social animals, creatures whose survival depends on working together
它们都是群居动物，通过共同工作来生存，
and being sensitive to each other's needs.
对彼此的需求很敏感。
And that might not be a coincidence.
这可能不是巧合。
One idea is that contagious yawning is related to empathy,
一个观点是传染性哈欠与同理心
or the ability to put yourself into someone else's shoes.
或者是设身处地为别人着想的能力有关。
Various studies have repeatedly shown that people who have impaired social skills,
各种研究一再表明，社会技能受损的人
including those with autism and schizophrenia,
包括那些患有自闭症和精神分裂症的人，
are less likely to yawn sympathetically than their peers.
与同龄人相比，打哈欠的可能性更小。
And kids below the age of four are also much less susceptible to contagious yawning than older children or adults.
4岁以下的儿童比大孩子或成人更不易受传染性哈欠的影响。
Psychologists also point to experiments that find yawning is more contagious
心理学家还指出，实验发现，如果最初打哈欠的人离你较近，
if the original yawner is someone close to you.
你会更容易传染打哈欠。
Both chimpanzees and humans are more likely to yawn if they see someone familiar yawn, versus a stranger.
黑猩猩和人类如果看到熟悉的同类打哈欠，会比看到陌生同类更容易传染打哈欠。
Since we tend to be more empathetic to members of our own group,
因为我们对自己群体的成员更有同感，
this bias suggests that contagious yawning could be rooted in empathy.
这种偏见表明，传染性哈欠可能根植于同理心。
That being said, a more recent study in autistic children found that their inability to catch a yawn
话虽如此，最近一项针对自闭症儿童的研究发现，他们没有能力去传染呵欠，
might be because they're not looking at people's faces, rather than a lack of empathy.
这可能是因为他们不看别人的脸，而不是缺乏同理心。
In two sets of experiments with about two dozen children with autism,
在针对24名自闭症患儿的两组实验中，
about 30% yawned contagiously, the same rate as developmentally normal children
如果患儿被告知要数一下打哈欠人的胡子或眼镜，
if they were told to count the beards or glasses of the people yawning.
那么大约30%的人会传染性地打哈欠，这一概率与发育正常的儿童相同，
In other words, if the kids were directed to look at the faces, they became just as likely to yawn.
换句话说，如果孩子们被引导着去看脸，他们很可能会打哈欠。
But for scientists who think that empathy plays at least some part in contagious yawning,
科学家认为同理心至少在传染性哈欠方面有些作用，对他们来说，
one hypothesis is that mirror neurons are involved in the brain.
有种假设是镜像神经元与大脑有关。
These neurons form networks
这些神经元形成网络
and are thought to fire if a person is doing a task or watching someone else do the same task.
如果一个人在做一项任务或者看别人做同样的任务时，它们会被激活。
This way, the thinking goes, the neurons "mirror" those actions and can help with mimicry, and maybe empathy.
这种思维方式是，神经元“反映”这些行为，并能帮助模仿它们，或许还能感同身受。
In support of this, a handful of small fMRI studies have found
为了支持这一点，几个小型功能磁共振成像（fMRI）研究发现，
that mirror neurons light up when volunteers watch videos or listen to sound recordings of other people yawning.
当志愿者观看视频或听其他人打哈欠的录音时，镜像神经元会激活。
But as appealing as this idea is, some scientists aren't so sure that mirror neurons are responsible.
尽管这个想法很吸引人，但一些科学家仍不确定镜像神经元是否有责任。
Other fMRI studies of contagious yawning haven't seen any mirror neuron activation.
其他关于传染性哈欠的fMRI研究还没有发现任何镜像神经元的激活现象。
And neuroscientists are still debating the function and location of mirror neurons in the human brain.
神经科学家们还在讨论镜像神经元在人脑中的功能和位置。
A different way scientists explain contagious yawning is simply that motor areas of the brain,
科学家对传染性哈欠的另一种解释是大脑的运动区域
like the ones that control your facial movements, are easily excitable.
比如控制你面部运动的区域，很容易兴奋。
A study published this past summer measured the excitability of motor neurons in three dozen people
去年夏天发表的一项研究测量了30多人
while they watched videos of others yawning.
在看其他人打哈欠视频时的运动神经元的兴奋性，
They used a technique called transcranial magnetic stimulation, or TMS,
他们使用了一种叫做经颅磁刺激（TMS）的技术，
in which a coil that's generating a magnetic field is passed across the head.
它的线圈产生的磁场能穿过头部。
And this magnetic field can be used to stimulate and measure electrical signals in neurons.
这个磁场可以用来刺激和测量神经元中的电信号。
The researchers found that people with more natural activity in those neurons were more likely to yawn.
研究人员发现，这些神经元中有更多自然活动的人更容易打哈欠。
In fact, differences in neuronal activity explained about half of the variation in whether a person yawned or not.
事实上，神经元活动的差异解释了一个人打哈欠与否的一半变化。
And when some other scientists tested for correlations between empathy test scores and catching yawns,
当其他一些科学家测验同理心测试得分和传染哈欠之间的相关性时，
they also found that different people might just have inherently different susceptibility.
还发现不同的人可能天生就有不同的易感性。
In one study of more than 300 adults,
在一项针对300多名成年人的研究中，
researchers showed participants a 3-minute video of other people yawning.
研究人员让参与者看了一段其他人打哈欠的3分钟视频。
How likely a person was to yawn in response didn't have anything to do with how empathetic they were.
一个人打哈欠的可能性与他们的同理心没有任何关系。
Instead, it was more related to age, with younger adults yawning more than middle-aged or older adults.
相反，它与年龄更相关，年轻人的哈欠超过了中年或老年人。
Also, the scientists noticed that each person seemed to have a hardwired level of sensitivity to contagious yawning.
此外，科学家们注意到，每个人似乎对传染性哈欠都有一种天生的敏感度。
Some people yawned a lot over multiple sessions,
有些人在多次会议上打了很多哈欠，
and others never opened their mouths at all.
有些人根本就没开口。
These results jive well with the motor neuron excitability idea,
这些结果支持运动神经元兴奋性的观点
although they still leave a lot of questions unanswered,
尽管仍有许多悬而未决的问题，
like why we've evolved this reaction in the first place.
比如为什么我们一开始就进化了这个反应。
In any case, for a lot of us, it doesn't take much to yawn if we see someone else do it.
无论如何，对于我们很多人来说，它对我们看到其他人打哈欠没有多大影响。
There's even a good chance a lot of you automatically yawned just while watching this video.
在观看这段视频的时候，很多人会自动打哈欠。
And if you haven't yet, I'll give you one more reason.
如果你还没有，我再给你一个理由。
Thanks for watching this episode of SciShow Psych!
感谢您收看本期的心理科学秀！
If you want to learn more about this kind of stuff,
如果你想了解更多这方面的内容，
check out our video where Hank talks about a phenomenon called groupthink,
看看我们的视频，汉克谈到了一种叫做群体思维的现象，
which is basically how your friends can affect your opinions.
它基本上讲得是你的朋友如何影响你的意见。
And don't forget to go to youtube.com/scishowpsych and subscribe!
不要忘了登录youtube.com/scishowpsych点击订阅哦！
