He's extended your nervous system with one very long neuron

他用一個非常長的神經元擴展了你的神經系統。

to a target about 70 meters away.

到大約70米外的目標。

At some point, he's going to fire an arrow.

在某些時候，他要射箭。

If you can then think a thought to the target before the arrow hits it,

如果可以的話，那麼在箭矢射中目標之前，你就對著目標想一想。

he'll let you go.

他會讓你走的

So who wins that race?

那麼誰會贏得這場比賽呢？

In order to answer, we have to examine the hardware of thought: neurons.

為了回答，我們必須研究思維的硬件：神經元。

The human brain has about 86 billion of these cells.

人腦中大約有860億個這樣的細胞。

They transmit signals down their axons by way of electrical impulses,

它們通過電脈衝的方式將信號傳遞到軸突上。

or action potentials.

或動作電位。

One neuron can then pass that signal to the next at a synapse

一個神經元可以在突觸處將該信號傳遞給下一個神經元。

by way of chemical neurotransmitters.

通過化學神經遞質的方式。

The signal is received by the next neuron's dendrites,

信號由下一個神經元的樹突接收。

propagated down its axon, and passed further along.

傳播到其軸突上，並進一步沿。

So, the key factors that determine how quickly you think

所以，決定你思維速度的關鍵因素是什麼？

include how long it takes to generate an initial action potential;

包括產生初始行動潛力所需的時間；

propagate it down the length of the axon; and transport it through the synapse.

沿著軸突的長度傳播；並通過突觸運輸。

We must also factor in the number of neurons involved

我們還必須考慮到參與的神經元數量

and the distance the signal has to travel.

以及信號要走的距離。

Let's see what this looks like in a simple pathway— your knee-jerk reflex.

讓我們來看看這看起來像一個簡單的途徑--你的膝跳反射。

A strike to your patellar tendon triggers an electrical impulse

髕骨肌腱受到撞擊會引發電脈衝

that travels up a sensory neuron to your spine.

傳送到你的脊柱的感覺神經元。

There the signal branches, and for the sake of simplicity,

有信號分支，為了簡單。

we'll consider the segment that jumps into a motor neuron

我們將考慮到跳入運動神經元的部分

to journey back down your leg.

沿著你的腿往回走。

The total length of the neurons in that pathway

該路徑中神經元的總長度。

is about 1 meter in someone who is 5 foot 5 inches,

在一個身高5英尺5英寸的人身上，大約是1米。

and on average it takes 15 to 30 milliseconds from strike to kick.

而從出手到踢出，平均需要15到30毫秒。

Speed is distance divided by time,

速度是距離除以時間。

so this signal travels somewhere between 120 to 240 kilometers per hour.

所以這個信號的時速在120到240公里之間。

The initial action potential accounts for 1 to 5 milliseconds

最初的動作電位佔1至5毫秒。

and synaptic transmissions only take .1 to .5 milliseconds,

而突觸傳輸只需要0.1到0.5毫秒。

so the bulk of that time is spent within the axons.

所以大部分時間是在軸突內度過的。

This is consistent with research findings

這與研究結果一致

that the average individual neuron sends signals at around 180 kilometers per hour.

平均單個神經元以每小時180公里左右的速度發送信號。

But speeds can be boosted with myelination and increased axon diameter.

但速度可以通過髓鞘化和增加軸突直徑來提升。

Myelin is a fatty sheath that insulates an axon,

髓鞘是一種隔絕軸突的脂肪鞘。

preventing electrical currents from leaking out.

防止電流外洩。

Meanwhile, axons with larger diameters offer less internal resistance.

同時，直徑較大的軸突提供的內阻較小。

These compounded factors can raise the speed of an action potential

這些複合因素可以提高動作電位的速度。

as high as 432 kilometers per hour.

高達每小時432公里。

There's plenty of variation: some people think faster than others,

有很多變化：有些人的思維比別人快。

and your own speed of thought changes throughout your lifetime.

而自己的思維速度在一生中也會發生變化。

In particular, as you reach old age,

尤其是到了老年。

the myelin sheath covering your axons wears down,

覆蓋在你的軸突上的髓鞘磨損了。

and other neuronal structures degrade.

和其他神經元結構退化。

Back to the dastardly experiment.

回到卑鄙的實驗中去。

Arrows shot from recurve bows fly, on average,

彎弓射出的箭平均會飛。

around 240 kilometers per hour.

每小時240公里左右。

Which means that given a sufficiently long, myelinated or large-diameter neuron,

也就是說，給定一個足夠長的、有髓的或大直徑的神經元。

your thoughts actually could win the race.

你的想法其實可以贏得比賽。

But… there's a wrinkle.

但是... ... 有一個皺紋。

The arrow and thought don't leave the gate at the same time;

箭頭和思想不要同時離開大門。

first the arrow fires, then once you perceive it,

先是箭在弦上，然後一旦察覺。

your signal can start down its path.

你的信號可以開始它的路徑。

Processing images or music, participating in inner speech,

處理影像或音樂，參與內心的言語。

and recalling memories all require complicated neural pathways

和回憶記憶都需要複雜的神經通路。

that are nowhere close to the linearity of the knee-jerk reflex.

與膝跳反射的直線性相差甚遠。

The speed at which these thoughts occur is mostly consistent,

這些念頭發生的速度大多一致。

with variations based on myelination and axon diameter.

與基於髓鞘和軸突直徑的變化。

But the duration of a thought will vary significantly depending on its routes,

但一個念頭的持續時間會因其路線不同而有很大的不同。

pitstops, and destination.

停靠站和目的地。

In this case, when you perceive a threatening stimulus,

在這種情況下，當你感知到一個威脅性的刺激時。

you'll invoke a fear startle response.

你會引起恐懼的驚嚇反應。

Similar to the knee-jerk response,

類似於膝蓋的反應。

a startle can be involuntary and quite fast.

驚嚇可以是不自主的，而且相當快。

If the string twangs loud enough,

如果琴絃顫動的聲音足夠大。

you might react in less than 65 milliseconds.

你可能會在65毫秒內做出反應。

More likely though, your startle reaction will be based on sight.

不過更有可能的是，你的驚嚇反應會基於視覺。

Our eyes can process an image as quickly as 13 milliseconds,

我們的眼睛可以以13毫秒的速度處理影像。

but computation of what you're seeing and determining the danger it poses

但計算你所看到的東西，並確定它所帶來的危險。

can take as long as 180 to 200 milliseconds.

可能需要180到200毫秒之久。

In that time the arrow will have gained a head start of about 13 meters.

屆時，箭頭將獲得13米左右的起點。

The target is far enough away

目標足夠遠

that you've got just enough of a chance to catch up,

你有足夠的機會趕上。

if you can quickly, and quite literally, think your way out.

如果你能迅速地，相當字面上，想出你的辦法。