Sarah-Jayne Blakemore: The mysterious workings of the adolescent brain

Translator: Joseph Geni Reviewer: Morton Bast

譯者: Yu-Sheng Lin 審譯者: Barry Hu

Fifteen years ago, it was widely assumed

在15年前, 大家普遍地認為

that the vast majority of brain development

腦部的發育成長, 主要都在

takes place in the first few years of life.

剛出生的前幾個年頭發生

Back then, 15 years ago, we didn't have the ability

在15年前做研究的人

to look inside the living human brain

並無法觀察到活生生的人的腦部運作

and track development across the lifespan.

更談不上追蹤人的一生期間的腦部發展

In the past decade or so, mainly due to advances

但在過去的十年間

in brain imaging technology

主要由於腦部造影技術的發展

such as magnetic resonance imaging, or MRI,

例如: 核磁共振造影, 簡稱 MRI

neuroscientists have started to look inside the living

神經學研究者開始有辦法看到, 各年齡層的

human brain of all ages, and to track changes

活生生的人的腦部運作, 並且追蹤隨著時間

in brain structure and brain function,

腦部結構與功能所發生的改變

so we use structural MRI if you'd like to take a snapshot,

因此，若要觀察腦部結構, 我們會使用結構性的MRI

a photograph, at really high resolution of the inside

一張高解析度的照片, 可以看到活著的人的

of the living human brain, and we can ask questions like,

腦內結構, 可以解答我們的這些疑問, 例如:

how much gray matter does the brain contain,

大腦裡的灰質占了多少?

and how does that change with age?

隨著年齡又有什麼樣的變化

And we also use functional MRI, called fMRI,

我們也可以使用功能性的MRI, 又稱 fMRI

to take a video, a movie, of brain activity

來拍攝大腦活動的影片

when participants are taking part in some kind of task

被拍攝的人同時正在進行某項工作

like thinking or feeling or perceiving something.

比如思考或感覺或感知某些事物

So many labs around the world are involved in this kind

世界各地有很多實驗室都在參與這種

of research, and we now have a really rich

研究，我們現在擁有大量的觀察資料

and detailed picture of how the living human brain develops,

記錄活的人的腦部發展的的詳細照片/影片

and this picture has radically changed the way

這些影像資料完全改變了

we think about human brain development

我們對人類大腦發展的觀點

by revealing that it's not all over in early childhood,

資料顯示了, 人腦並非僅在童年早期就發展完畢

and instead, the brain continues to develop

相反的, 大腦持續在發展, 延續到

right throughout adolescence and into the '20s and '30s.

整個青春期, 一直到 廿幾 到 卅幾 歲 都還在發展

So adolescence is defined as the period of life that starts

青春期的定義, 是一段生命的期間, 始於

with the biological, hormonal, physical changes of puberty

生物上的、 內分泌上的、 身體上的改變

and ends at the age at which an individual attains

一直到個人建立了一個社會中的

a stable, independent role in society.

穩定而且獨立的地位的時間為止

(Laughter)

（笑聲）

It can go on a long time. (Laughter)

青春期有可能延續的很長久（笑聲）

One of the brain regions that changes most dramatically

在青春期, 腦部劇烈改變的區域之一,

during adolescence is called prefrontal cortex.

叫做 前額葉皮層。

So this is a model of the human brain,

這裡是一個人的腦部的模型

and this is prefrontal cortex, right at the front.

而這是前額葉皮層，就在前面。

Prefrontal cortex is an interesting brain area.

前額葉皮層是一個有趣的大腦區域。

It's proportionally much bigger in humans than

比例上來說, 人腦的前額葉皮層遠大於

in any other species, and it's involved in a whole range of

任何其他物種，這個腦部區域負責一系列的

high level cognitive functions, things like decision-making,

抽象認知功能，如決策，

planning, planning what you're going to do tomorrow

規劃，規劃你明天要做的事情

or next week or next year, inhibiting

或是下星期或明年，這個腦區也會抑制

inappropriate behavior, so stopping yourself saying

不適當的行為，比方阻止你自己說出

something really rude or doing something really stupid.

一些粗魯的話語, 或是做很蠢的事情

It's also involved in social interaction,

這個腦區也涉及社會互動，

understanding other people, and self-awareness.

瞭解其他人, 還有自我知覺

So MRI studies looking at the development of this region

有些 MRI 研究觀察了這個腦區的發展

have shown that it really undergoes dramatic development

發現在這個區域經歷了劇烈的變化

during the period of adolescence.

在青春期的期間

So if you look at gray matter volume, for example,

例如, 就 灰質的體積來說

gray matter volume across age from age four to 22 years

從4歲到22歲的期間, 灰質的體積

increases during childhood, which is what you can see

在兒童時期開始增加, 如同你在投影片上看到的

on this graph. It peaks in early adolescence.

增加到頂的時候, 大約是青春期的早期

The arrows indicate peak gray matter volume

兩個箭頭標示著 前額葉皮層 灰質最高的時間點

in prefrontal cortex. You can see that that peak happens

你可以看到這個最高點在女生較早發生

a couple of years later in boys relative to girls,

而男生的最高點則晚了一兩年

and that's probably because boys go through puberty

這有可能是因為男孩進入青春期的年紀

a couple of years later than girls on average,

普遍來說比女孩晚上一兩年

and then during adolescence, there's a significant decline

然後在後續的青春期, 數值就明顯地下降

in gray matter volume in prefrontal cortex.

前額葉皮層的灰質體積一路降低

Now that might sound bad, but actually this is

這聽起來好像不太好, 但事實上

a really important developmental process, because

這是真正重要的發展過程，因為

gray matter contains cell bodies and connections

灰質包含細胞本體, 還有細胞間的連接器

between cells, the synapses, and this decline

又稱為 神經突觸，

in gray matter volume during prefrontal cortex

這段期間發生的額葉皮層的灰質減少

is thought to correspond to synaptic pruning,

被解讀成 突觸 修剪的過程

the elimination of unwanted synapses.

把不需要的神經突觸刪去

This is a really important process. It's partly dependent

這是一個非常重要的過程。有一部分是因為

on the environment that the animal or the human is in,

這個動物或人類所處的環境的影響

and the synapses that are being used are strengthened,

讓有用到的突觸變強

and synapses that aren't being used

而在所處環境下用不到的突觸

in that particular environment are pruned away.

就被修剪掉了。

You can think of it a bit like pruning a rosebush.

你可以把它想像如同修剪薔薇叢。

You prune away the weaker branches so that

你會把較弱的分支剪掉

the remaining, important branches, can grow stronger,

讓留下來的, 較重要的分支, 可以長得更好

and this process, which effectively fine-tunes brain tissue

這樣的過程, 有效地微調了腦部的組織

according to the species-specific environment,

來因應該物種所處的特定的環境

is happening in prefrontal cortex and in other brain regions

這個過程 發生在前額葉皮層, 還有大腦的其他區域

during the period of human adolescence.

在人類青春期的期間。

So a second line of inquiry that we use to track changes

第二層的研究, 是用功能性的 MRI (fMRI)

in the adolescent brain is using functional MRI

來追蹤青春期的腦部的變化

to look at changes in brain activity across age.

各個年齡階段腦部活動狀況有什麼改變

So I'll just give you an example from my lab.

這裡用我的實驗室的一個例子來說明

So in my lab, we're interested in the social brain, that is

我的實驗室研究的是 "社交腦"，就是

the network of brain regions that we use to understand

大腦各區域的相互連結, 讓人類可以理解

other people and to interact with other people.

其他人，並與其他人進行互動。

So I like to show a photograph of a soccer game

這裡我想展示一張在足球賽裡拍的照片

to illustrate two aspects of how your social brains work.

來說明你的 社交腦 運作的兩個面向

So this is a soccer game. (Laughter)

在這場足球賽裡（笑聲）

Michael Owen has just missed a goal, and he's lying

麥克 · 歐文 剛剛射門沒進，他正躺在地上

on the ground, and the first aspect of the social brain

你的社交腦的第一個面向

that this picture really nicely illustrates is how automatic

可以用這張照片貼切的展現出來, 就是 社交情緒

and instinctive social emotional responses are,

是如此自動且本能的流露出來

so within a split second of Michael Owen missing this goal,

所以只在 麥克 · 歐文 射門沒進的 幾分之一秒裡

everyone is doing the same thing with their arms

每個人的反應都一樣, 雙手抱頭

and the same thing with their face, even Michael Owen

臉上的表情也都一樣, 就連 麥克 · 歐文

as he slides along the grass, is doing the same thing

在滑倒在草皮上的時候, 也是相同的動作與表情

with his arms, and presumably has a similar

雙手也抱著頭, 臉上應該也是一樣的表情

facial expression, and the only people who don't

而照片中有議群與眾不同的

are the guys in yellow at the back — (Laughs) —

是在後面的黃色的傢伙 — — （笑） — —

and I think they're on the wrong end of the stadium,

我想他們應該是坐錯邊了, 跑到敵隊陣營裡了

and they're doing another social emotional response

他們有著另一種社交情緒反應

that we all instantly recognize, and that's the second aspect

我們大家都馬上就認出來了, 這也是社交腦的第二個面向

of the social brain that this picture really nicely illustrates,

透過這張找片很好地展現了

how good we are at reading other people's behavior,

我們是多麼地善於解讀別人的舉動

their actions, their gestures, their facial expressions,

從 他們的行動，他們的手勢，臉部表情，

in terms of their underlying emotions and mental states.

可以知道他們蘊含的情感與心裡面的狀態

So you don't have to ask any of these guys.

所以你不必開口問這些人

You have a pretty good idea of what they're feeling

就能相當了解他們的感受

and thinking at this precise moment in time.

還有在那個時刻的他們的想法

So that's what we're interested in looking at in my lab.

這就是我的實驗室有興趣研究的

So in my lab, we bring adolescents and adults into the lab

所以在我的實驗室, 我們邀來了青少年和成人

to have a brain scan, we give them some kind of task

來進行腦部掃描，我們會給他們一些任務

that involves thinking about other people, their minds,

任務中涉及了, 猜測其他人心裡想什麼

their mental states, their emotions, and one of the findings

其他人的精神狀態、 情緒。我們有一項發現

that we've found several times now, as have other labs

我們重覆觀察到好幾次, 也有其他的實驗室

around the world, is part of the prefrontal cortex called

在世界其他地方觀察到，大腦前額葉皮層的一部分

medial prefrontal cortex, which is shown in blue on the slide,

叫做 內側前額葉皮層，在投影片上標示藍色的地方

and it's right in the middle of prefrontal cortex

就在 前額葉皮層的中間

in the midline of your head.

在你的頭中線。

This region is more active in adolescents when they make

青少年的這個區域變得更加活躍, 當他們進行

these social decisions and think about other people

一些社交決定, 還有想到其他人的時候

than it is in adults, and this is actually a meta-analysis

成人相對就沒那麼活躍。這項分析集合了

of nine different studies in this area from labs around

這個領域在全球各地的實驗室的九項不同研究結果

the world, and they all show the same thing, that activity

所有研究都顯示了相同的狀況, 就是

in this medial prefrontal cortex area decreases

內側前額葉皮層區的活動降低的現象

during the period of adolescence.

出現在青春期的被觀察者腦部

And we think that might be because adolescents and adults

我們認為這可能是由於青少年和成人

use a different mental approach, a different

使用不同的思維方式，不同

cognitive strategy, to make social decisions,

認知策略，來進行社交的決定

and one way of looking at that is to do behavioral studies

要研究這件事的方法之一, 是透過行為研究

whereby we bring people into the lab and we give them

我們把人請到實驗室裡, 並請他們

some kind of behavioral task, and I'll just give you

進行某些行為上的工作項目。這裡我會說明

another example of the kind of task that we use in my lab.

另一個例子, 關於在實驗室中採用的工作項目

So imagine that you're the participant in one of our

想像一下, 你是我們請來參與實驗的其中一人

experiments. You come into the lab,

你走進實驗室，

you see this computerized task.

你看到這個電腦化的任務。

In this task, you see a set of shelves.

在此任務中，你看到一組貨架。

Now, there are objects on these shelves, on some of them,

這些貨架上有些格子裡擺了東西

and you'll notice there's a guy standing behind the set

你會注意到有一個人站在貨架的另一邊

of shelves, and there are some objects that he can't see.

而且有一些格子的東西他是看不到的

They're occluded, from his point of view, with a kind of

這些格子從他那邊看, 是被擋住的, 他只看得到

gray piece of wood.

灰色的木板

This is the same set of shelves from his point of view.

這是他的方向看過來的同一個貨架

Notice that there are only some objects that he can see,

請注意, 他只能所看到的一部分的物件

whereas there are many more objects that you can see.

而從你這邊, 你可以看到更多的物件

Now your task is to move objects around.

現在你的任務是要移動物件。

The director, standing behind the set of shelves,

站在貨架對面的人是指揮者

is going to direct you to move objects around,

將會給你搬動物件的指令

but remember, he's not going to ask you to move objects

但是請記住，他不會叫你去搬動那些

that he can't see. This introduces a really interesting

他看不到的物件。這就帶來了非常有趣狀況:

condition whereby there's a kind of conflict

其中存在著一種衝突性

between your perspective and the director's perspective.

就是你的視角與指揮者的視角的不同

So imagine he tells you to move the top truck left.

所以想像若他告訴, 把最上層的卡車向左移

There are three trucks there. You're going to instinctively

你看得到三輛卡車, 本能地你會想去搬

go for the white truck, because that's the top truck

白色的卡車，因為這是最上層的卡車

from your perspective, but then you have to remember,

從您的角度看，但是你要記得

"Oh, he can't see that truck, so he must mean

"哦，他看不到那輛卡車，所以他說的應該是

me to move the blue truck," which is the top truck

要我搬藍色的卡車" 這才是最上層的卡車

from his perspective. Now believe it or not,

從他的角度看。那麼, 不知道你信不信

normal, healthy, intelligent adults like you make errors

像你這樣的正常、 健康、 聰明的成人, 出錯的

about 50 percent of the time on that kind of trial.

比例大概是 50%, 在這樣的實驗裡.

They move the white truck instead of the blue truck.

他們去搬白色卡車, 而不是藍色的。

So we give this kind of task to adolescents and adults,

我們把這樣的工作交給參加實驗的青少年與成人

and we also have a control condition

我們也設計了一個控制組

where there's no director and instead we give people a rule.

在控制組沒有指揮者, 而是我們給定了一個規則,

We tell them, okay, we're going to do exactly the same thing

我們告訴他們，好吧，我們要做完全一樣的事情

but this time there's no director. Instead you've got to

但這次沒有指揮者。而是你自己要記得

ignore objects with the dark gray background.

去忽略掉黑灰色背景格子裡的物件。

You'll see that this is exactly the same condition, only

你可以看到這是完全相同的狀況, 唯一的差別

in the no-director condition they just have to remember

是在沒有指揮者的控制組, 他們只要記得

to apply this somewhat arbitrary rule, whereas

用上這條多少有點隨心所欲的規則, 而在

in the director condition, they have to remember

有指揮者那組, 他們必須記得

to take into account the director's perspective

要考慮到指揮者的視角

in order to guide their ongoing behavior.

來決定他們要進行的動作

Okay, so if I just show you the percentage errors

好, 那我要讓大家看看出錯的百分比的數據

in a large developmental study we did,

來自我們所進行的一個大型的發展研究

this is in a study ranging from age seven to adulthood,

研究對象的年齡層從七歲到成年

and what you're going to see is the percentage errors

你將會看到的是出錯的百分比

in the adult group in both conditions,

在成人族群中, 實驗組與控制組的數據圖

so the gray is the director condition, and you see

灰色的是有指揮者的狀況, 你可以看到

that our intelligent adults are making errors about 50 percent

這些聰明的成人大概有50%的犯錯比例

of the time, whereas they make far fewer errors

而他們出錯的比例相對來說低了很多

when there's no director present, when they just have

在沒有指揮者的狀況下, 在他們只要

to remember that rule of ignoring the gray background.

自己記得那條規則, 忽略掉灰色背景的格子

Developmentally, these two conditions develop

從發展的過程來看, 兩組的發展趨勢

in exactly the same way. Between late childhood

幾乎是完全相同的。從兒童期的後段,

and mid-adolescence, there's an improvement,

到青春期的中段, 一直都有進步

in other words a reduction of errors, in both of these trials,

換句話說, 出錯率降低了, 在兩種實驗都如此

in both of these conditions.

在這兩個年齡層也都如此。

But it's when you compare the last two groups,

但當您比較最後兩組數據

the mid-adolescent group and the adult group

青春期中段 與 成年人

where things get really interesting, because there, there is

就變得很有意思了, 因為在這兩個階段之間

no continued improvement in the no-director condition.

沒有指揮者狀況下, 出錯率並沒有變低了

In other words, everything you need to do in order to

換句話說，你所需要的關於去

remember the rule and apply it seems to be fully developed

記住規則和應用規則的部分, 似乎已經完全發展好了

by mid-adolescence, whereas in contrast,

在青春期中段之前就完成了，而相比之下，

if you look at the last two gray bars, there's still

如果你看看最後兩個灰色線條，仍有

a significant improvement in the director condition

很明顯的進步, 在有指揮者的部分

between mid-adolescence and adulthood, and what

從 青春期 中段 到成年還是有進步

this means is that the ability to take into account someone

這代表了, 把其他人的觀點列入考量

else's perspective in order to guide ongoing behavior,

來導引所進行的行為的能力

which is something, by the way, that we do in everyday life all

這也是我們日常生活每天都在做的事情

the time, is still developing in mid-to-late adolescence.

這種能力在青春期的中段到後段仍然在發展

So if you have a teenage son or a daughter and you

因此，若你剛好有十幾歲的兒子或女兒

sometimes think they have problems taking other people's

而且你有時候會覺得他們不太容易接納別人的觀點

perspectives, you're right. They do. And this is why.

你的感覺沒錯, 他們確實如此, 你也知道為什麼了

So we sometimes laugh about teenagers.

所以我們有時候會笑青少年

They're parodied, sometimes even demonized in the media

他們被醜化, 有時甚至被媒體妖魔化

for their kind of typical teenage behavior. They take risks,

只因為他們的一些典型的青少年舉動，他們會冒險

they're sometimes moody, they're very self-conscious.

他們有時喜怒無常，他們的自我意識很強

I have a really nice anecdote from a friend of mine

我有一個朋友告訴我一個小故事

who said that the thing he noticed most

我朋友說, 他所注意到

about his teenage daughters before and after puberty

關於他的十幾歲的女兒, 在青春期前後最大的變化

was their level of embarrassment in front of him.

是女兒在他面前受窘的程度

So, he said, "Before puberty, if my two daughters

他說到, 在青春期之前, 如果我的兩個女兒

were messing around in a shop, I'd say, 'Hey,

在一家店裡胡鬧, 我會說: "嘿!

stop messing around and I'll sing your favorite song,'

別再胡鬧了, 我就唱一首你們最愛聽的歌"

and instantly they'd stop messing around and he'd sing

而當他開始唱她們最喜歡的歌,

their favorite song. After puberty, that became the threat.

女兒們馬上就停止胡鬧。而在青春期之後，這招就變成威脅了

(Laughter)

（笑聲）

The very notion of their dad singing in public

她們想到爸爸在公眾場合唱歌這件事

was enough to make them behave.

就足以讓她們守規矩了

So people often ask,

所以人們常會問，

"Well, is adolescence a kind of recent phenomenon?

"嗯，青春期是最近流行的一種現象嗎?

Is it something we've invented recently in the West?"

這是西方社會最近才發明出來的嗎?"

And actually, the answer is probably not. There are lots

其實答案很可能是否定的。歷史上有很多

of descriptions of adolescence in history that sound

關於青春期的描寫, 聽起來

very similar to the descriptions we use today.

跟我們現在描寫的方式很相像。

So there's a famous quote by Shakespeare from "The Winter's Tale"

在莎士比亞的《冬天的故事》有一句名言

where he describes adolescence as follows:

他是這樣描寫 青春期 的:

"I would there were no age between ten and

"我想, 在十歲和廿三歲之間, 是沒有年齡的

three-and-twenty, or that youth would sleep out the rest;

不然年輕應該會在其餘的時間沉睡

for there is nothing in the between but getting wenches

因為在這段歲月中沒有什麼事值得做, 除了讓女僕懷孕、

with child, wronging the ancientry, stealing, fighting." (Laughter)

敗壞古風、 偷竊、 打架"。（笑聲）

He then goes on to say, "Having said that, would any

他接著說，"儘管如此，除了這些

but these boiled brains of nineteen and two-and-twenty

十九歲到廿二歲的燒壞的腦袋, 還會有什麼人

hunt in this weather?" (Laughter)

在這種天氣出來打獵啊？"（笑聲）

So almost 400 years ago, Shakespeare was portraying

所以近 400 年前，莎士比亞所描繪的

adolescents in a very similar light to the light that we

青少年的形象，跟我們現在描繪的非常相近

portray them in today, but today we try to understand

而在今天我們試著去理解

their behavior in terms of the underlying changes

他們的行為, 從他們身體裡的

that are going on in their brain.

腦部發展的變化

So for example, take risk-taking. We know that adolescents

所以, 就以冒險來當例子, 我們知道青少年

have a tendency to take risks. They do.

有冒險的傾向。他們的確如此。

They take more risks than children or adults,

他們比兒童或成人更願意冒險，

and they are particularly prone to taking risks

他們特別喜歡冒險, 尤其是

when they're with their friends. There's an important drive

當他們與他們的朋友一起的時候。這存在著一種重大的驅動力

to become independent from one's parents

想要脫離父母親而變得獨立

and to impress one's friends in adolescence.

並且想讓他的同齡朋友印象深刻

But now we try to understand that in terms of

現在我們可以試著去理解這件事, 從

the development of a part of their brain called the limbic system,

他們大腦的稱為邊緣系統一部分的發展過程來看

so I'm going to show you the limbic system in red

我給大家展示的圖上, 紅色部分就是邊緣系統

in the slide behind me, and also on this brain.

在我身後的投影片，還有手上的這個腦模型

So the limbic system is right deep inside the brain,

這個邊緣系統位於大腦的深處

and it's involved in things like emotion processing

它負責的事情包括 情感處理

and reward processing. It gives you the rewarding feeling

獎勵處理。它會讓你感受到回饋

out of doing fun things, including taking risks.

從做一些有趣的事情中產生, 包括冒險

It gives you the kick out of taking risks.

他驅使你去冒險

And this region, the regions within the limbic system,

而這個腦區, 這個包含在邊緣系統內部的區域

have been found to be hypersensitive to the rewarding

已經被觀察到, 對於冒險所產生的回饋感覺

feeling of risk-taking in adolescents compared with adults,

在青少年的身上, 是超級敏感, 相較於成人而言

and at the very same time, the prefrontal cortex,

而在這個時期, 正好也是 前額葉皮層，

which you can see in blue in the slide here,

就是在投影片中的藍色區域

which stops us taking excessive risks,

也是阻止我們過度冒險的腦部區域

is still very much in development in adolescents.

在青少年時期, 卻仍然還在發展中

So brain research has shown that the adolescent brain

所以透過研究大腦，我們知道青春期的大腦

undergoes really quite profound development,

正經歷深刻的改變

and this has implications for education, for rehabilitation,

這對於 教育 還有 復健 與 矯正措施, 有相當的意義

and intervention. The environment, including teaching,

整個環境，包括教學，

can and does shape the developing adolescent brain,

可以也實際上會影響青少年大腦的發育，

and yet it's only relatively recently that we have been

而相對來說, 西方世界也只是從最近, 才開始

routinely educating teenagers in the West.

經常教育青少年

All four of my grandparents, for example, left school

以我的祖父母為例，他們四個人在離開學校的時候

in their early adolescence. They had no choice.

都是在青春期前段, 他們沒有選擇。

And that's still the case for many, many teenagers

而還有很多很多像這樣的案例,

around the world today. Forty percent of teenagers

今天全世界的青少年。有 40%

don't have access to secondary school education.

沒有接受中學教育

And yet, this is a period of life where the brain is

然而，在生命的這個階段，正是大腦

particularly adaptable and malleable.

特別具有適應性和可塑性的期間

It's a fantastic opportunity for learning and creativity.

也正是學習和創新的大好機會。

So what's sometimes seen as the problem

所以有些被視為問題的事情

with adolescents — heightened risk-taking, poor impulse

關於青少年的 — —高漲的冒險企圖，孱弱的衝動控制

control, self-consciousness — shouldn't be stigmatized.

自我意識 — — 不應該被污名化

It actually reflects changes in the brain that provide

這些實際上反映了大腦中的變化, 也提供了

an excellent opportunity for education

極好的機會, 來施以教育

and social development. Thank you. (Applause)

和社交能力的發展。謝謝。（掌聲）

(Applause)

（掌聲）