What percentage of your brain do you use? - Richard E. Cytowic

翻译人员: Zhou Sijia 校对人员: Angelique Wang

An enduring myth says we use only 10% of our brain,

一个经久不衰的迷思声称

我们只运用大脑的十分之一

the other 90% standing idly by for spare capacity.

剩下的百分之九十只不过是备用的存储而已

Hucksters promised to unlock that hidden potential

某些假行家声称可以用“基于神经科学”的方法

with methods "based on neuroscience,"

来开发那90%的隐藏潜力

but all they really unlock is your wallet.

但他们真正打开的不过是你的钱包。

Two-thirds of the public and nearly half of science teachers

三分之二的大众

以及近半数的科学教师

mistakenly believe the 10% myth.

误以为人只能用十分之一大脑的声明是真的。

In the 1890s, William James,

在 19 世纪 90 年代，威廉 · 詹姆斯，

the father of American psychology, said,

美国心理学之父

"Most of us do not meet our mental potential."

曾说，"我们大多数人是不能开发

我们全部的脑力潜能"。

James meant this as a challenge,

詹姆斯的话意味着这是一项挑战，

not an indictment of scant brain usage.

而并非控诉我们大脑较少的使用率。

But the misunderstanding stuck.

但这个误会一直困扰着大家。

另外，在很长一段时间里

Also, scientists couldn't figure out for a long time

科学家们想不出

the purpose of our massive frontal lobes

我们脑内大量的额叶

or broad areas of the parietal lobe.

或大面积的顶叶的用途。

Damage didn't cause motor or sensory deficits,

并且因为额叶和顶叶的损伤并不会引起运动或感觉神经的缺失，

so authorities concluded they didn't do anything.

所以研究人员断定他们没有任何作用。

For decades, these parts were called silent areas,

几十年来，这些部位

被称为沉默区域，

their function elusive.

他们真正的作用令人难以琢磨。

We've since learned that they underscore

我们既然已经知道他们重视

executive and integrative ability,

执行和综合能力，

without which, we would hardly be human.

所以一旦失去他们，我们几乎就失去了人类的基本能力。

They are crucial to abstract reasoning,

他们对我们抽象推理的能力、

planning, weighing decisions

规划、

做决定

and flexibly adapting to circumstances.

和是否能很快的适应环境有着至关重要的作用。

The idea that 9/10 of your brain sits idly by in your skull

那个十分之九的大脑

在你的脑袋里袖手旁观的理论，

looks silly when we calculate how the brain uses energy.

在我们计算大脑怎样消耗能量时显得毫无道理。

啮齿动物和犬齿动物的大脑消耗

Rodent and canine brains

consume 5% of total body energy.

身体总能量的 5%。

Monkey brains use 10%.

猴子使用其大脑的10%。

An adult human brain,

成人的大脑，

which accounts for only 2% of the body's mass,

仅占全身质量的2%，

consumes 20% of daily glucose burned.

每日却消耗20%的葡萄糖。

In children, that figure is 50%,

而儿童消耗50%的葡萄糖，

and in infants, 60%.

婴儿要消耗60%。

This is far more than expected for their relative brain sizes,

这组数值远远超出了我们的预想，

因为他们不同的

which scale in proportion to body size.

大脑相对于整个身体的质量。

Human ones weigh 1.5 kilograms,

人的大脑重 1.5 公斤，

elephant brains 5 kg,

大象大脑重5 公斤，

and whale brains 9 kg,

鲸鱼大脑重9 公斤，

yet on a per weight basis,

然而这每一公斤里面，

humans pack in more neurons than any other species.

人类的大脑比其他物种的大脑

有更多的神经元。

This dense packing is what makes us so smart.

我们人类正是因为紧密排列的神经元才会如此聪明。

There is a trade-off between body size

在体重和神经元数量之间

and the number of neurons a primate,

有一个平衡点，

including us, can sustain.

这就是灵长类动物（包括我们人类）可以承受的数量。

A 25 kg ape has to eat 8 hours a day

一个25公斤重的猿每天要进食8个小时，

to uphold a brain with 53 billion neurons.

才能使装有530亿个神经元的大脑正常运作。

The invention of cooking,

烹饪的发明，

one and half million years ago,

那是大约150万年前的事情，

gave us a huge advantage.

在进化方面带给了我们巨大的优势。

Cooked food is rendered soft and predigested

煮熟的食物较为松软

outside of the body.

且在入口前已经过预消化。

Our guts more easily absorb its energy.

我们的内脏更容易吸收它的能量。

Cooking frees up time and provides more energy

烹饪节省时间

并提供了更多的能量，

than if we ate food stuffs raw

相比于我们吃生食物来说。

and so we can sustain brains

所以我们可以维持

with 86 billion densely packed neurons.

拥有860 亿密集神经元的大脑的正常运转，

比猿大脑内的神经元数量多出40%。

40% more than the ape.

Here's how it works.

这里是它的工作原理：

Half the calories a brain burns

大脑消耗的一半卡路里

go towards simply keeping the structure intact

都只是简单地为了保持大脑结构的完好无损

by pumping sodium and potassium ions

用钠离子和钾离子

across membranes to maintain an electrical charge.

渗透过细胞膜来保持胞内电荷平衡。

To do this, the brain has to be an energy hog.

要做到这一点，大脑则必须有强有力的能量。

It consumes an astounding

大脑每分钟都令人震惊地消耗 3.4 x 10 ^21 个三磷酸腺苷（ATP） 分子，

3.4 x 10^21 ATP molecules per minute,

ATP being the coal of the body's furnace.

三磷酸腺苷就好像支持我们身体燃烧的燃料。

The high cost of maintaining resting potentials

在所有 860 亿神经元里面

in all 86 billion neurons

保持（细胞的）静息电位的 高消耗，

means that little energy is left

意味着只剩下很少的一点能量

to propel signals down axons and across synapses,

来把信号送到神经轴突和神经突触，

the nerve discharges that actually get things done.

实际上是神经放电这个过程在真正起作用。

Even if only a tiny percentage of neurons

即使只有很少一部分的神经元

fired in a given region at any one time,

在任一时间的某一区域被发射，

the energy burden of generating spikes over the entire brain

在整个大脑内

因生成峰值而产生的能量负担

would be unsustainable.

会使其不能长时间负荷。

因此就需要高效利用能源。

Here's where energy efficiency comes in.

Letting just a small proportion of cells signal at any one time,

只让一小部分的细胞

在某一时间被发射出来，

known as sparse coding,

这个叫做稀疏编码的过程，

uses the least energy,

仅用最少的能量，

but carries the most information.

但却能承载最多的的信息。

Because the small number of signals

因为少量的信号

have thousands of possible paths by which to distribute themselves.

有成千上万种可能的路径

来到达目的地。

A drawback of sparse coding within a huge number of neurons

但稀疏编码在大量的神经元内

却有一个缺点，

is its cost.

那就是它的成本。

Worse, if a big proportion of cells never fire,

更糟糕的是，如果有大量的细胞从来没有被发射出去，

then they are superfluous

那他们都是多余的了

and evolution should have jettisoned them long ago.

自然选择在很长时间以前就应该把它们摒弃了。

The solution is to find the optimum proportion of cells

解决办法是要去找到

可以立刻激活大脑的

that the brain can have active at once.

最佳数量比例的细胞。

For maximum efficiency,

为使效率最大化，

between 1% and 16% of cells should be active at any given moment.

在任何时间

1%~16%之间的细胞应该被激活。

This is the energy limit we have to live with

这是我们为了意识的清醒

必须容忍的

in order to be conscious at all.

能量限制。

The need to conserve resources

为了节省资源

is the reason most of the brain's operations

是大部分大脑的运作

must happen outside of consciousness.

必须发生在意识之外的原因。

It's why multitasking is a fool's errand.

这就是为什么同时处理多项任务是很傻的差事。

We simply lack the energy to do two things at once,

我们只是单纯缺乏同时做两件事情的能量

let alone three or five.

更不用说三件事甚至五件事情了。

When we try, we do each task less well

当我们尝试同时处理多项任务的时候，每一项任务就会

than if we had given it our full attention.

比我们全力以赴做一件事情的时候成效要差。

The numbers are against us.

这些数字是反对我们同时执行多任务的。

你的大脑已经够聪明强大了。

Your brain is already smart and powerful.

So powerful that it needs a lot of power to stay powerful.

它需要很多的能量才能

保持如此强大。

And so smart

大脑是如此的聪明，

that it has built in an energy-efficiency plan.

它已然建立了一个能源效率计划。

So don't let a fraudulent myth make you guilty

所以不要让一个骗人的谎言

让你对你

about your supposedly lazy brain.

据说很懒惰的大脑感到愧疚。

Guilt would be a waste of energy.

罪恶感也是会浪费能源的。

After all this,

经过这一切...

don't you realize it's dumb to waste mental energy?

你难道没有意识到

浪费精力是很傻的举动吗？

You have billions of power-hungry neurons to maintain.

你需要维持数十亿

非常消耗能量的神经元的正常工作。

So hop to it!

所以赶快让他正常运作起来吧！