Have you ever yawned

別人打哈欠

because somebody else yawned?

你會不會也打哈欠？

You aren't especially tired,

其實沒有特別累

yet suddenly your mouth opens wide

但突然就張大嘴巴

and a big yawn

一個大哈欠

comes out.

就跑出來了

This phenomenon is known as contagious yawning.

這現象叫哈欠傳染

And while scientists still don't fully understand

對於背後的原因

why it happens,

科學家還不完全了解

there are many hypotheses currently being researched.

但已經有人在研究各種假說

Let's take a look at a few

讓我們來了解

of the most prevalent ones,

一些廣為流傳的說法

beginning with two physiological hypotheses

先聽聽 2 種生理假說

before moving to a psychological one.

再看看 1 種心理假說

Our first physiological hypothesis

第 1 種生理假說認為

states that contagious yawning

哈欠傳染其來有自

is triggered by a specific stimulus,

會由特定刺激引起

an initial yawn.

就是最初的哈欠

This is called fixed action pattern.

這叫固定行為模式

Think of fixed action pattern like a reflex.

有點像反射動作

Your yawn makes me yawn.

你的哈欠讓我打哈欠

Similar to a domino effect,

類似多米諾骨牌效應

one person's yawn triggers a yawn

一個人的哈欠

in a person nearby that has observed the act.

讓附近看到的人也打哈欠

Once this reflex is triggered,

這效應一旦啟動

it must run its course.

就會持續一定的時間

Have you ever tried to stop a yawn

快打哈欠時

once it has begun?

你有試過阻止自己嗎？

Basically impossible!

根本不可能！

Another physiological hypothesis

第 2 種生理假說

is known as non-conscious mimicry,

叫無意識模仿

or the chameleon effect.

又稱變色龍效應

This occurs when you imitate someone's behavior

人會模仿他人的行為

without knowing it,

下意識地

a subtle and unintentional copycat maneuver.

做出細微、自然的複製動作

People tend to mimic each other's postures.

人會模仿他人的姿勢

If you are seated across from someone

像是對面的人翹腳

that has their legs crossed,

你看到了

you might cross your own legs.

很有可能也會翹起腳來

This hypothesis suggests

這假說認為

that we yawn when we see someone else yawn

看到別人打哈欠就跟進

because we are unconsciously copying

是因為不知不覺中

his or her behavior.

我們會模仿他人的行為

Scientists believe that this chameleon effect

科學家相信

is possible because of a special set of neurons

變色龍效應可能和特殊的神經元有關

known as mirror neurons.

也就是鏡像神經元

Mirror neurons are a type of brain cell

鏡像神經元是一群腦細胞

that responds equally when we perform an action

像鏡子一樣

as when we see someone else

看到他人的動作後

perform the same action.

我們會做出相同的動作

These neurons are important

這組神經元很重要

for learning and self-awareness.

尤其對學習和自我覺察

For example, watching someone do something physical,

例如，看到別人的動作

like knitting

像是編織

or putting on lipstick,

或是擦口紅

can help you do those same actions more accurately.

能讓我們精確地做出相同的動作

Neuroimaging studies using fMRI,

腦神經影像利用醫學技術

functional magnetic resonance imaging,

也就是功能性核磁共振造影

shows that when we seem someone yawn

發現看到別人打哈欠

or even hear their yawn,

或只是聽到哈欠聲

a specific area of the brain

我們腦中

housing these mirror neurons

有鏡像神經元的區塊

tends to light up,

會有反應

which, in turn, causes us to respond

促使我們做出回應

with the same action: a yawn.

重複相同的動作：打哈欠

Our psychological hypothesis also involves

最後要談的心理假說

the work of these mirror neurons.

也和鏡像神經元有關

We will call it the empathy yawn.

稱為同理哈欠

Empathy is the ability to understand

同理心是種能力

what someone else is feeling

能感知他人的感受

and partake in their emotion,

融入對方的情緒

a crucial ability for social animals like us.

對人這種社會性動物很重要

Recently, neuroscientists have found

近來，神經學家發現

that a subset of mirror neurons

鏡像神經元有組子集

allows us to empathize with others' feelings

能讓我們同理他人

at a deeper level.

而且是深層同理

Scientists discovered

事實上

this empathetic response to yawning

同理哈欠現象

while testing the first hypothesis we mentioned,

是在測試固定行為時

fixed action pattern.

所發現的

This study was set up to show

這研究假設

that dogs would enact a yawn reflex

如果狗聽到人類打哈欠

at the mere sound of a human yawn.

也會反射性地打起哈欠

While their study showed this to be true,

不僅證實了這種現象

they found something else interesting.

還發現了其他有趣的事

Dogs yawned more frequently at familiar yawns,

熟人的哈欠對狗比較有影響力

such as from their owner's,

像是主人

than at unfamiliar yawns from strangers.

但對陌生人就不是了

Following this research,

同樣地

other studies on humans and primates

以人類和靈長類為研究對象

have also shown that contagious yawning

也證實哈欠傳染

occurs more frequently among friends than strangers.

在熟人間發生的機率高於陌生人

In fact, contagious yawning starts occurring

事實上，早在4、5 歲時

when we are about four or five years old,

對哈欠傳染就有反應了

at the point when children

那時

develop the ability to identify others' emotions properly.

兒童開始能正確了解他人的情緒

Still, while newer scientific studies aim

儘管相關研究推陳出新

to prove that contagious yawning

想證明哈欠傳染的產生

is based on this capacity for empathy,

是因為同理能力

more research is needed

但其實

to shed light on what exactly is going on.

更需要研究的是背後的機制

It's possible that the answer lies

說不定真正的答案

in another hypothesis all together.

就藏在其他假說裡

The next time you get caught in a yawn,

下次打哈欠時

take a second to think about what just happened.

停下來想想剛才的情形

Were you thinking about a yawn?

是不是想到了哈欠這件事？

Did someone near you yawn?

附近有人打哈欠嗎？

Was that person a stranger or someone close?

是熟人？還是陌生人？

And are you yawning right now?

你現在在打哈欠嗎？