No human gets to escape this moody, angsty, confusing phase

每個人都會經歷這段情緒起伏、易怒且困惑的時期

And interestingly, such an extended adolescence is unique to humans.

有趣的是，這麼長的青春期是人類獨有的

Other animals grow up a lot faster than we do.

其他動物的成長速度比人類快許多

And you may think our teen years are just about streamlining bodies for baby making,

也許你會認為青春期只是讓身體成熟，以迎接生小孩的階段

but as it turns out, the storm of sex hormones that we associate with the teenage years,

一提到青春期，我們就會聯想到大量的荷爾蒙變化

are only a small part of what's really going on in the teenage body.

但事實上荷爾蒙的變化只是青春期的一小部分

Most of the action, it turns out, is happening in the brain.

大腦才是影響青春期的關鍵

Until fairly recently, we thought that the brain finished the nuts and bolts of its development,

直到最近，我們都認為大腦的發育

by the time we started kindergarten. But really,

在上幼稚園之前就差不多完成了

right as puberty rolls in, it undergoes massive remodeling.

但事實上，進入青春期後，大腦會經歷許多變化

This amounts to several years of neural growing pains, as well as the

造成青春期孩子數年的生長痛，再加上

other more visible growth that's going on all over your body.

其他更明顯的身體發育

So take heart!

聽好了！

Whether you're going through it now, or about to go through it,

不管你是正在經歷青春期、或是即將經歷

or count yourself among the veterans of that turbulent decade,

還是已經非常習慣這個混亂的時期

know that the result of the teen years is a stronger, faster, more sophisticated brain.

要知道青春期過後，會擁有發育更好、更快也更成熟的大腦

If there were someone that told me twenty years ago...

可惜二十年前沒人告訴我件事…

Let's start with that obvious scapegoat of adolescent anguish, hormones.

首先，荷爾蒙被認為是青春期焦躁不安的罪魁禍首

That word itself, is kind of a lazy shorthand that people use

荷爾蒙 (hormone) 是簡稱，用來形容

to describe the chemicals that some of our glands secrete, that can affect our behavior.

腺體分泌的化學物質，而它會影響人類行為

But the fact is, hormones have all kinds of jobs that have nothing to do with where you grow hair,

但事實上，荷爾蒙有很多其他作用和你毛髮生長在哪裡、

or what turns you on, or whether you feel glum for no apparent reason

什麼使你興奮和莫名其妙的情緒低落都沒有關係

Hormones keep your heart beating, and your body hydrated, and they make your organs grow,

荷爾蒙讓心臟跳動、讓身體保有水份、讓器官生長

and make you grow bone, and muscle, and skin!

讓你長出骨頭、肌肉與皮膚

What people actually mean when they talk about "teenage hormones", are sex hormones.

大家談論「青少年荷爾蒙」時其實談的都是性荷爾蒙

And yes, puberty involves a whole series of sex hormone storms,

的確，性荷爾蒙在青春期很活躍

the first of which actually kicks in before you're out of Primary School.

小學畢業前就會第一次感受到性荷爾蒙影響

That's when the Adrenal glands starts secreting androgens, which triggers the growth

這段期間由於腎上腺體分泌雄性激素

in activity of the skin's sebaceous glands, making skin more oily.

刺激皮膚分泌油酯的腺體，使皮膚出油

Soon enough, more apocrine or sweat glands get activated increasing body odor.

很快地，更多頂漿腺與汗腺會運作，加重體味

Then comes the wave of hormonal agents that start activating the gonads.

接著大量的荷爾蒙帶動性腺分泌

For boys, this influx of luteinizing hormones from the pituitary gland, get testosterone from the testes,

以男性來說，腦下垂體釋放促黃體激素後，使睪丸釋出睪酮

and suddenly, that guy has up to fifty times more testosterone than he did before puberty.

因此男性在青春期釋出的睪酮比青春期前多五十倍

This also changes the shape of the male body, promoting hair growth,

睪酮也會改變男性的身形，刺激毛髮生長

and building up lean muscle mass,

促進肌肉組織生長

just as the increased presence of estrogen in girls rearranges the deposition of their fats,

就如女性的卵激素會讓體內脂肪分布改變一樣

stimulating the growth of breasts.

刺激乳房的生長

Humans are actually lucky to experience the craziness of puberty only once,

人類只要經歷一次青春期，其實算幸運了

many other animals undergo multiple similarly intense hormonal rodeos as they enter sexually active periods,

每到繁殖季節，許多動物都會經歷多次類似的大量荷爾蒙混亂時期

sometimes called the rut or heat, every new breeding season.

有時我們把這種現象叫做發情期

Some male species completely stop eating during their breeding period,

有些雄性動物在繁殖季節完全不進食

because they're just that sex crazed.

因為他們一心想要交配

And yet all that said, teens are far less ruled than their hormones than you might think.

即使如此，青少年受到的賀爾蒙影響比你想像中更少

There are other factors that play here.

還有其他原因

For example, your favorite moody teen may be by turns punchy, angry, depressed, or in a zombie like fog,

例如，你的孩子可能一下激動、一下憤怒、突然憂鬱，又突然如行屍走肉般

because of their chronic lack of sleep.

就因為他們長期缺乏睡眠

Sleep is vital to everyone, but it's specially important for kids and teens, because it's during sleep

睡眠對每個人都很重要，特別是小孩和青少年

that your pituitary gland releases an essential growth hormone, necessary for development.

睡覺時，腦下垂體會釋出重要的成長激素，對發育相當重要

A normal sleep cycle driven by circadian rhythm is regulated by the daytime release of cortisol,

一般睡眠循環是由生理時鐘控制，白天釋出的可體松

which helps you wake up, and melatonin, which helps you wind down when it gets dark.

讓人體知道起床時間，夜晚釋出褪黑激素，讓人天黑後放鬆下來

But this biology of sleep timing changes as we age and as puberty begins, teens' sleep clocks get pushed back.

睡眠時間會隨年紀變化，青春期開始後會延後青少年的睡眠時間

Most adults start oozing melatonin around 10 p.m. ish, but one study showed that teenagers

大多數成人晚上十點前後會分泌褪黑激素，有一項研究顯示青少年

don't start producing melatonin until closer to 1am! This may be because puberty's hormonal frenzy

將近凌晨一點才開始分泌褪黑激素，可能由於體內的荷爾蒙

is stalling the release of melatonin, and could partly explain why so many teens stay up late,

使褪黑激素的釋放減緩，便可以解釋很多青少年為何熬夜

energized by the night, but had a really hard time rolling out of bed with the alarm.

他們夜晚精神特別好，早上要起床特別痛苦

Of course it's a bit of a chicken and egg deal, since watching reruns of The Simpsons,

當然這有點像是雞生蛋、蛋生雞的問題，畢竟熬夜看辛普森家庭

and playing Call of Duty late at night continues to stimulate the brain,

和打電動仍然會刺激大腦

which may further delay the release of melatonin. Still, some researchers are starting to advocate

延遲褪黑激素的釋放

for pushing back high school start times in the morning,

許多研究人員仍提倡高中延遲第一堂課的時間

in the hopes of having more focused students.

想讓學生上課更能全神貫注

So we've got sex hormones changing the bodies, and a lack of sleep to contend with,

即使有體內的性荷爾蒙變化、睡眠不足為理由，

but increasing evidences suggest that, there is something much bigger at work

有更多的研究顯示，其實背後有更重要的因素

that's making teenagers so 'teenager-ry'.

讓青少年如此「青少年」

Their brains!

就是大腦！

It turns out that brains actually take longer than we thought, to fully mature.

大腦發育完全成熟的速度比我們想像地還慢

I don't mean physical size - our brains are already about 95% full-sized by the time we're just six -

這並非指大腦的大小，大腦早在我們六歲時就發育了95%

but more in the sense of the connections inside the brain.

大腦在青春期時最重要的是發展內部的連結

Adults, for the most part, know how to make decisions by evaluating choices, and weighing consequences.

大多數成人會衡量自己的選擇與後果

They do this with their prefrontal cortex,

這都是大腦中前額葉皮質的功勞

which is responsible for controlling impulses and emotions, and forming judgments.

前額葉皮質負責控制衝動與情緒、做出判斷

Its neurons chat with the neurons in other regions of the brain, responsible for - say it - memory or movement,

這部分的神經細胞會和其他部分的神經細胞溝通

through synapses.

例如透過突觸和負責記憶與動作的神經細胞溝通

The thing is, teenage brains don't quite work like this yet. The prefrontal cortex may not be fully developed

但因為青少年的前額葉皮質還尚未發育完全，大腦還無法這樣運作

until you're mid-twenties, and teen synapses - those ''lines'' of communication - are still growing,

人一直到20多歲，那些神經突觸，溝通用的條狀「觸手」，仍持續生長

and specializing.

並各司其職

They're also -

發展速度

slow.

也很慢

As an adolescent brain keeps developing, its axons - the long ''tail-like'' parts of the neurons

青少年的大腦在發育時，神經軸突，神經細胞長條狀的部分

that transmit signals to other neurons - become more and more insulated

用來傳遞訊息的軸突會有像絕緣體一般的髓磷脂包覆

by a fatty layer called the 'Myelin Sheath'. This padding greatly increases the cell's transmission speed,

層狀髓磷脂會加快細胞傳遞訊息的速度

and while it helps adults make faster decisions, it isn't fully formed in teens.

幫助成人更快做出決定，但青少年這區塊還未發育完全

These changes occur slowly, beginning at the back of the brain, where the oldest and most fundamental

這些改變來的慢，以後腦為起點，也就是大腦發育最早也最基本的區塊

brain parts reside, and slowly working its way forward to the more advanced and complicated brain bits.

接著才會慢慢往前腦發展，前腦較後腦精密、複雜

The prefrontal cortex is the last to be hooked up and shaped.

前額葉皮質最後才會發育、成形

So it's important to keep in mind, that just because your favorite teenager stayed up until sunrise

一定要記得，如果你的小孩隔天要考試

binge-watching 'The Walking Dead' the night before an exam, it doesn't mean they're dumb or lazy,

還看陰屍路看到天亮，這不代表他們懶惰或笨

their brain are just literally finishing being built.

而是他們的大腦才剛剛結束發育

But at the same time, because all this brain building's just starting to peak,

但同時也因為他們大腦的發育已到達頂點

this is also, when the brain starts getting thinned out.

這也是大腦的灰質開始減少的時候

You actually start losing connections that you don't use enough, in a process called synaptic pruning -

不常用來傳遞訊息的神經元會無法作用，這個過程叫作「突觸修剪」(synaptic pruning)

which has led to a theory that this is kind of a 'use it or lose it' phase.

進而得出「用進廢退」這樣的理論

Meaning,

意思就是

adolescence could be an specially important time to use your brain -

青少年時期要好好地運用大腦

play an instrument;

學樂器

engage in sports;

運動

write poetry;

寫詩

learn a language!

學語言

Because by doing these things, you're helping to hardwire those synapses, and giving your brain topiary

做這些事讓神經突觸活躍，刺激大腦

a lovely lasting shape. Whereas if you're sitting around all day playing Candy Crush,

如果你只是整天坐著玩 Candy Crush

those will be the connections that survive,

大腦就算有了這個技能

which you don't need...

也無用武之地啊

This shaping of the teen brain manifests itself in other ways too, like in teenage attitudes.

大腦的發育結果很容易看得出來，拿青少年的態度做例子

A group of scientist at the McLean Hospital of Massachusetts, once hooked up a group of adults

麻州麥克林醫院的科學家曾讓成人與青少年參加研究

and a group of teens, to MRI devices and then asked them to identify a series of expressions

要他們分辨照片上成人的情緒，利用斷層掃描監控大腦活動

on photographs of adults faces. Interestingly, while adults correctly identified one expression as fear,

有趣的是，成人有辦法看出照片上的人感到恐懼

the teenagers thought the faces showed anger, surprise, or shock. They weren't registering subtleties well.

但青少年卻以為是憤怒、驚訝或驚嚇，無法分辨這些情緒間微小的差別

Not only that, but the MRI images showed that adults and teens responded with different parts of their brains.

除此之外，研究結果顯示成人與青少年是用大腦不同區塊去分辨的

Adults, use the reasonable prefrontal cortex, while the teens mostly use the gut reaction, emotional amigdala,

成人用掌管理性前額葉皮質，青少年則大多靠直覺、或用掌管情緒的杏仁核分辨

located farther back in the brain.

杏仁核 (amygdala) 位在大腦後方

Results like these might help explain why teenagers seem to experience frequent mood swings.

這樣的結果或許可以解釋青少年的情緒多變

For one, they tend to react quickly from the emotional part of their brain,

第一，因為他們掌管情緒的區塊反應迅速

without running those reactions by the more rational frontal cortex,

並沒用到掌管理性的前額葉皮質

and two, it could be that they're just misreading expressions, and therefore the intentions behind them.

第二，他們也有可能誤判臉部表情，導致誤判情緒

The frontal cortex also helps people relate to, and understand each other,

前額葉皮質也讓人有同理心、理解彼此

and you can imagine what happens when concern is misjudged as anger; or worry, as disappointment.

當「關心」被誤解成「憤怒、擔憂」或「失望」時，誤會可就大了

The Fresh Prince has an entire song about it.

Fresh Prince 影集就是最佳例子了

But the truth is, as much as parents just don't understand, teens don't always understand either.

事實上，父母不了解這點，青少年自己也不懂

When the emotional amigdala, and the more rational cortex aren't fully hooked up yet,

當杏仁核與前額葉皮質還未能完全連接時

that can make it hard for teenagers to productively work through emotions.

青少年很難去掌控自己的情緒

This kind of reactionary, impulsive behavior may also lead to more risk taking.

這種靠直覺、衝動的行為也會讓他們不顧自身去犯險

Adolescence is the time when we're most likely to experiment with whatever booze, drugs, or toad licking is available,

青少年時期是最有可能接觸酒或毒品的時期

and unfortunately, it's also the time our developing brains are most vulnerable to lasting effects

不幸的是，這時期也是大腦發育定型的關鍵時期

Studies have shown that teens are more likely to become addicted to drugs and alcohol, than adults

研究顯示青少年比成人更容易沈迷於毒品和酒精

partly because their brains are more attuned to their reward centers.

因為他們的大腦看重的是「獎勵」

While the teenage prefrontal cortex is still developing, their 'Nucleus Accumbens',

前額葉皮質還在發育的同時

or 'pleasure and reward zone', forms early on.

伏隔核 (Nucleus Accumbens)，大腦中掌管「享樂與獎賞」的區域已經開始發育

Neuroimaging studies have shown that when presented with a big potential reward,

神經影像研究顯示青少年有個大獎賞的話

teen brains light up way more than kids or adults brains, but if the reward was small,

他們的大腦會比小孩和成人更加活躍，但如果獎勵不高

teen brains hardly fired at all.

就無法提起他們的興趣

So basically, give an adolescent a pat on the back, and you'll get a shrug.

基本上，你好聲好氣地說什麼，他們也漫不在乎

Give them a hot date or a winning goal, and their brains light up like Vegas.

但如果是約會或獲勝目標，他們的大腦會像賭城一樣活躍起來

This of course, does not always result in great judgment.

他們在這樣情況下不一定都有好的判斷能力

A jacked up thrill-seeking impulse, combined with exquisite pang of peer pressure,

可能原因是尋求快感的衝動、龐大的同儕壓力

plus a new driver's license, new sex parts, and access to substances can lead to some not good results.

加上拿到新駕照、新發育的性器官、接觸那些讓他們誤入歧途的物品

But still, this long and some times tedious remodeling process that our bodies go through in the teenage years,

但是，青春期這段漫長且無趣的大腦變化過程

isn't all that.

不僅僅如此而已

Many scientists have pointed out that our delayed adolescence

許多科學家指出青春期延遲

lets our brains keep their flexibility longer, which

讓大腦的彈性保持更久

Yeah, may make teens a little slow, but also more adaptable, as they prepare for the adult world.

這讓青春期延長，卻也在他們成年前增加適應能力

In this way, you can see teen impulsiveness as boldness; or independent thinking, and moodiness,

這樣一來，你就能把衝動當作勇敢或獨立思考

as a source of new found empathy; and excitability, as passion.

情緒多變看成另一種的同理心、興奮當作熱血

Which means, there's a lot of awesome energy floating around out there ready to decrease

也就是說，這些正向態度與能量能讓他們做好準備

all kinds of world suck.

去應付大人的現實世界

Thanks for watching this SciShow infusion, and thanks specially to all of our subscribers on Subbable,

感謝收看 SciShow，也特別感謝所有在 Subbable 的訂閱觀眾

who make this channel possible!

有你們才有這個頻道

You can be an honorary associate producer of SciShow, or even pick the topic of a future episode!

你們也能協助 SciShow 製作或選擇未來的主題

To find out how, go to ''subbable.com/scishow''

更多詳情請見 subbable.com/scishow

And you can always find us on Facebook and Twitter, and in the comments below,

歡迎到我們的臉書、推特或在影片下方留言

and if you wanna keep getting smarter with us here at SciShow,

想從 SciShow 知道更多嗎？

you can go to "youtube.com/scishow" and subscribe.

歡迎訂閱 SciShow 的 Youtube 頻道：youtube.com/scishow