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  • An enduring myth says we use

    有個歷久不衰的傳說

  • only 10% of our brain.

    說我們只用了大腦的 10%

  • The other 90% standing idly by for spare capacity.

    其餘的 90% 閒著備用

  • Hucksters promised to unlock that hidden potential

    賣膏藥的人保證你能釋放潛能

  • with methods "based on neuroscience,"

    用「有神經科學根據」的方法

  • but all they really unlock is your wallet.

    但實際只釋放了你的錢包

  • Two thirds of the public

    三分之二的大眾

  • and nearly half of science teachers

    和近半的科學老師

  • mistakenly believe the 10% myth.

    誤信這 10% 的傳說

  • In the 1890s, William James,

    1890 年代,威廉‧詹姆士

  • the father of American psychology,

    美國心理學之父

  • said, "Most of us do not meet

    說:「大部分的人都沒有充分發揮

  • our mental potential."

    他們的心智潛能」

  • James meant this as a challenge,

    詹姆士意指這是一個挑戰

  • not an indictment of scant brain usage.

    而不是指控很少用腦

  • But the misunderstanding stuck.

    但這誤解延續至今

  • Also, scientists couldn't figure out

    還有,科學家長久以來

  • for a long time

    都搞不清楚

  • the purpose of our massive frontal lobes

    我們巨大的額葉

  • or broad areas of the parietal lobe.

    或大面積的頂葉的功能

  • Damage didn't cause motor or sensory deficits,

    損傷並不會造成運動或感覺障礙

  • so authorities concluded they didn't do anything.

    所以科學家斷定它們沒用

  • For decades, these parts

    數十年來,這些部分

  • were called silent areas,

    被稱為 「寂靜區域」

  • their function elusive.

    他們的功能令人費解

  • We've since learned that they underscore

    我們後來得知它們強調

  • executive and integrative ability,

    執行及整合能力

  • without which, we would hardly be human.

    沒有它們,我們稱不上是人類

  • They are crucial to abstract reasoning,

    它們對於抽像推理

  • planning,

    計畫

  • weighing decisions

    衡量決定

  • and flexibly adapting to circumstances.

    及對各種情況的適應力非常重要

  • The idea that 9/10 of your brain

    你的大腦十分之九

  • sits idly by in your skull

    在顱腔內閒著的這個想法

  • looks silly when we calculate how the brain uses energy.

    看起來很蠢,如果我們計算 腦部如何使用能量

  • Rodent and canine brains consume

    齧齒類及犬類的腦消耗

  • 5% of total body energy.

    身體總能量的 5%

  • Monkey brains use 10%.

    猴子的腦使用 10%

  • An adult human brain,

    一個成年人的腦

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

    只占身體總質量的 2%

  • consumes 20% of daily glucose burned.

    卻消耗 20% 每日燃燒葡萄糖量

  • In children, that figure is 50%,

    而孩童,這數字是 50%

  • and in infants, 60%.

    而在嬰兒,60%

  • This is far more than expected

    這比預期高出許多

  • for their relative brain sizes,

    與他們相對的腦容量而言

  • which scale in proportion to body size.

    而腦容量與身體大小成正比

  • Human ones weigh 1.5 kilograms,

    人類的腦重 1.5 公斤

  • elephant brains 5 kg,

    大象的腦 5 公斤

  • and whale brains 9 kg,

    而鯨魚的腦 9 公斤

  • yet on a per weight basis,

    而以重量比來看

  • humans pack in more neurons

    人類裝了更多的神經元

  • than any other species.

    比其他物種都多

  • This dense packing is what makes us so smart.

    這種高密度填充 就是我們如此聰明的原因

  • There is a trade-off between body size

    靈長類動物在身體大小

  • and the number of neurons of primate,

    及能維持多少神經元之間

  • including us, can sustain.

    必須取得平衡,這也包括人類

  • A 25 kg ape has to eat 8 hours a day

    一隻 25 公斤的猩猩每天要吃 8 小時

  • to uphold a brain with 53 billion neurons.

    以維持牠腦內五百三十億個神經元

  • The invention of cooking,

    而發明烹調法

  • one and half million years ago,

    在 150 萬年前

  • gave us a huge advantage.

    給了我們巨大的優勢

  • Cooked food is rendered soft and predigested

    煮熟的食物使之變軟而且已在身體外

  • outside of the body.

    先消化過了

  • Our guts more easily absorb its energy.

    我們的腸胃更容易吸收它的能量

  • Cooking frees up time

    煮食釋放出時間

  • and provides more energy

    及提供更多能量

  • than if we ate food stuffs raw

    比之於我們吃生食

  • and so we can sustain brains

    所以我們才能維持腦內

  • with 86 billion densely packed neurons.

    八百六十億緊密填充的神經元

  • 40% more than the ape.

    比猩猩還多 40%

  • Here's how it works:

    這是它運作的方式

  • Half the calories a brain burns

    半數大腦燃燒的卡路里

  • go towards simply keeping the structure intact

    拿去維持結構不變

  • by pumping sodium and potassium ions

    由主動運輸鈉鉀離子

  • across membranes to maintain an electrical charge.

    通過細胞膜以維持電荷來達成

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

    要這樣做,大腦必須 是隻貪吃能源的豬

  • It consumes an astounding 3.4 x 10^21 ATP molecules per minute,

    它每分鐘要消耗驚人的 3.4 x 10^21 個三磷酸腺苷分子

  • ATP being the coal of the body's furnace.

    三磷酸腺苷是身體能源火爐的煤炭

  • The high cost of maintaining resting potentials

    要維持靜止電位的高代價

  • in all 86 billion neurons

    在全部八百六十億神經元中

  • means that little energy is left

    意指只有所剩無幾的能量

  • to propel signals down axons and across synapses,

    能輸出信號到軸突及穿越突觸

  • the nerve discharges that actually get things done.

    造成神經放電,也就是任務完成

  • Even if only a tiny percentage of neurons

    即使只有極少百分比的神經元

  • fired in a given region at any one time,

    在某個時段某個區域被激發

  • the energy burden of generating spikes

    其在整個大腦產生電衝動

  • over the entire brain

    所需的能量負擔

  • would be unsustainable.

    也是無法持續的

  • Here's where energy efficiency comes in.

    這是節能要起作用的地方

  • Letting just a small proportion of cells

    讓只有一小部分的細胞

  • signal at any one time,

    在任何一段時間發送信號

  • known as sparse coding,

    這被稱為稀疏編碼

  • uses the least energy,

    用最少的能量

  • but carries the most information.

    但傳遞最多的訊息

  • Because the small number of signals

    因為這少數的信號

  • have thousands of possible paths

    可以用數千種路徑

  • by which to distribute themselves.

    來傳遞

  • A drawback of sparse coding

    在這麼大量的神經元內

  • within a huge number of neurons

    稀疏編碼有個缺點

  • is its cost.

    就是成本很高

  • Worse, if a big proportion of cells never fire,

    更糟的是,如果一大部分的 細胞從未被激發

  • then they are superfluous

    那他們就是多餘的

  • and evolution should have jettisoned them long ago.

    演化早該在很久以前就把他們拋棄

  • The solution is to find

    解決的方法是找到

  • the optimum proportion of cells

    在某時刻內,腦內有多少

  • that the brain can have active at once.

    活躍的細胞的最佳比例

  • For maximum efficiency,

    要獲得最大的效率

  • between 1% and 16% of cells

    應該要有介於 1% 到 16% 間的細胞

  • should be active at any given moment.

    在任一時刻處在活躍狀態

  • This is the energy limit

    這是能量的限制

  • we have to live with

    我們必須與之共存

  • in order to be conscious at all.

    這是為了能保持有意識狀態

  • The need to conserve resources

    腦部需要節約資源

  • is the reason most of the brain's operations

    正是絕大部分的腦部運作

  • must happen outside of conciousness.

    都必須發生在意識以外的主要原因

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

    這就是為什麼多工只是徒勞無功

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

    我們就是沒有能量同時做兩件事

  • let alone three or five.

    就別提三件或五件事了

  • When we try, we do each task less well

    當我們試著多工,我們每件事的成效

  • than if we had given it our full attention.

    都比只專心做一件事要差

  • The numbers are against us.

    數字對我們不利

  • Your brain is already smart and powerful.

    你的大腦已經很聰明,威力強大

  • So powerful, that it needs a lot of power

    如此強大,它需要很多能量

  • to stay powerful.

    以保持強大

  • And so smart

    而且是如此聰明

  • that it has built in an energy efficiency plan.

    它已經內建了一個節能計畫

  • So don't let a fradulent myth

    所以不要讓一個不實的傳說

  • make you guilty about your

    讓你對

  • supposedly lazy brain.

    本應懶惰的大腦感到愧疚

  • Guilt would be a waste of energy.

    愧疚會浪費能量

  • After all this,

    在這長篇大論之後

  • don't you realize it's dumb to waste

    你難道還不明瞭浪費心智能量

  • mental energy?

    是件很蠢的事?

  • You have billions of

    你有數十億

  • power-hungry neurons to maintain.

    餓的要命的神經元要維持

  • So hop to it!

    所以快點上工吧!

An enduring myth says we use

有個歷久不衰的傳說

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B2 中高級 中文 TED-Ed 能量 神經元 大腦 身體 細胞

【TED-Ed】你的大腦用了多少 (What percentage of your brain do you use? - Richard E. Cytowic)

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    VoiceTube 發佈於 2014 年 03 月 26 日
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