neurological case studies. We’ll be looking at some of his fascinating research in future lessons,

這集節目中我們將會了解他的一些特別有趣的研究

but for now, I just want to talk about Sacks himself. Although he possesses

但首先，我希望能先介紹 Sacks這個人。儘管他有著

a brilliant and inquisitive mind, Dr. Sacks cannot do a simple thing that your average toddler can.

聰明過人且渴望求知的特質，Sacks博士卻沒辦法做到連三歲小孩都做得到的事

He can’t recognize his own face in the mirror.

他沒辦法在鏡子中辨認他自己的臉

Sacks has a form of prosopagnosia, a neurological disorder that impairs a person’s ability

Sacks患有臉孔識別障礙，那是一種神經疾病，患者會喪失識別臉孔的能力

to perceive or recognize faces, also known as face blindness. Last week we talked about

該症狀又被稱為臉盲症。上星期我們談到

how brain function is localized, and this is another peculiarly excellent example of that.

腦區是如何分工的，而這正是另一個典型的例子

Sacks can recognize his coffee cup on the shelf, but he can’t pick out his oldest

Sacks可以辨認出架子上的咖啡杯，但他卻無法認得

friend from a crowd, because the specific sliver of his brain responsible for facial

人群中的最老的那個朋友，因為他腦中負責辨識臉孔的區塊故障了

recognition is malfunctioning. There’s nothing wrong with his vision. The sense is intact.

他的視力並沒有任何問題，他的感官完全正常

The problem is with his perception, at least when it comes to recognizing faces.

問題出在他的知覺，至少在辨識臉孔上確定是有問題的

Prosopagnosia is a good example of how sensing and perceiving are connected, but different.

臉盲症是一個很好的例子來解釋感覺和知覺緊緊相關，但彼此不同

Sensation is the bottom-up process by which our senses, like vision, hearing and smell,

感覺是一個由下往上的傳遞過程，透過感覺我們得以感受周遭，像是視覺、聽覺以及味覺

receive and relay outside stimuli. Perception, on the other hand, is the top-down way our

接受並傳遞外在刺激。知覺則是由上往下，我們的腦統合並處理所接受到的資訊

brains organize and interpret that information and put it into context. So right now at this

形成認知。因此就在此刻

very moment, you’re probably receiving light from your screen through your eyes, which

你的眼睛正接收你的螢幕所散發出來的光波

will send the data of that sensation to your brain. Perception meanwhile is your brain

並將這些資訊傳遞到你的腦中。接著你的腦中形成知覺

telling you that what you’re seeing is a diagram explaining the difference between

使你了解你正在觀看一個解釋感覺與知覺相異之處的頻道

sensation and perception, which is pretty meta. Now your brain is interpreting that

聽起來像個迴圈。現在你的腦正處理眼睛接收到的資訊

light as a talking person, whom your brain might additionally recognize as Hank.

就好像光波在對你說話一樣，甚至你的腦也許能認出是Hank

We are constantly bombarded by stimuli even though we’re only aware of what our own

我們無時無刻都受到外在刺激的轟炸，即使我們僅能察覺到感官可以接收到的部分

senses can pick up. Like I can see and hear and feel and even smell this Corgi,

就像我可以看到、聽到、感覺到甚至聞到這隻柯基

but I can’t hunt using sonar like a bat or hear a mole tunneling underground like an owl or

但我沒辦法像蝙蝠一樣用聲納狩獵，或者像貓頭鷹一樣聽到鼴鼠在地底下挖洞的聲音

see ultraviolet and infrared light like a mantis shrimp. I probably can’t even smell

或者像蝦蛄一樣看見紫外光以及紅外光。我也許甚至無法

half of what you can smell. No! No! We have different senses. Mwah mwah mwah mwah mwah.

聞到你這傢伙聞到的一半多。不!不!我們有著不同的感受。唔嗯嗯嗯嗯嗯嗯嗯

Yeah.

呼，耶

There’s a lot to sense in the world, and not everybody needs to sense all the same stuff.

這世界上有許多種感覺，但不是所有生物都感知同樣的事物

So every animal has its limitations which we can talk about more precisely

每種動物都有其感知範圍，我們可以說得更精確一點

if we define the Absolute Threshold of Sensation, the minimum stimulation needed to register

假如我們定義感覺的絕對閾值，最低程度的刺激必須

a particular stimulus, 50% of the time. So if I play a tiny little beep in your ear and

有50%的機會引起反應。所以如果我在你耳朵旁邊播放一個很微小的嗶嗶聲

you tell me that you hear it fifty percent of the times that I play it,

然後你告訴我，在我播放的總次數中，其中有一半你聽到嗶嗶聲

that’s your absolute threshold of sensation. We have to use a percentage because sometimes I'll play

那這就是你聽覺的絕對閾值。我們必須要用百分比，因為有時我播放

the beep and you’ll hear it and sometimes you won’t even though it’s the exact same volume.

嗶嗶聲時你會聽到但有時不會，即使都是同樣的音量

Why? Because brains are complicated.

為什麼會這樣? 因為腦可是很複雜的

Detecting a weak sensory signal like that beep in daily life isn’t only about the

日常生活中，在察覺像是嗶嗶聲這樣微弱的訊號時，不只訊號源

strength of the stimulus. It’s also about your psychological state; your alertness and

的強度會有影響，你的精神狀態也會有影響。包括事件當下你的警覺性

expectations in the moment. This has to do with Signal Detection Theory, a model for

以及對事件的預期程度。這些都與訊息偵測理論有關，這是一個用來

predicting how and when a person will detect a weak stimuli, partly based on context.

預測一個人在什麼情況下可以感覺到微小刺激的模型。另外事件的背景也會有影響

Exhausted new parents might hear their baby’s tiniest whimper, but not even register the bellow

精疲力盡的新手父母也許能聽見小嬰兒最小的的嗚咽聲，但卻絲毫未覺

of a passing train. Their paranoid parent brains are so trained on their baby,

呼嘯而過的火車。家長偏執的腦非常專注於他們的嬰兒

it gives their senses a sort of boosted ability, but only in relation to the subject of their attention.

這使得他們部份的感官能力得到加強，但僅限於他們關注的事物

Conversely, if you’re experiencing constant stimulation, your senses will adjust in a

相反地，如果你正感受到持續的刺激，你的感官會進入

process called sensory adaptation. It is the reason that I have to check and see if my

一個稱為感覺適應的過程。這個過程使得我必須要查看我的右邊口袋

wallet is there if it’s in my right pocket, but if I move it to my left pocket,

確定我的錢包是否還在，但如果我把錢包放到左邊口袋

it feels like a big uncomfortable lump. It’s also useful to be able to talk about our ability

那就會像一個大型累贅。另一個實用的知識是關於能我們區分出兩個不同刺激來源

to detect the difference between two stimuli. I might go out at night and look up at the sky

的能力。當我在晚上出門並仰望夜空

and, well, I know with my objective science brain that no two stars have the exact same brightness,

透過我客觀的科學家腦袋我知道不存在兩顆完全相同亮度的星星

and yeah, I can tell with my eyeballs that some stars are brighter than others,

沒錯，我可以靠著眼睛分辨出某些星星比其他星星更亮

but other stars just look exactly the same to me. I can’t tell the difference in their brightness.

但對我來說剩下的星星看起來就完全沒差別了，我分辨不出他們亮度上的差異

Are you done? Is it time for your to go? Gimme, gimme a kiiiissss. Yes, yes. Okay. Good girl.

你想離開了?現在嗎?來吧，親一個。沒錯，沒錯，乖女孩

The point at which one can tell the difference is the difference threshold, but it’s not linear.

一個人能否分出差異取決於差異程度閾值，但該值並非線性

Like. if a tiny star is just a tiny bit brighter than another tiny star, I can tell.

假設一個小星星只有比另一個小星星亮那麼一丁點，我可以看出差異

But if a big star is that same tiny amount brighter than another big star, I won’t

但如果是一個很大的星星卻跟另一個很大的星星也只差了那麼一丁點，那我就無法

be able to tell the difference. This is important enough that we gave the guy who discovered

分辨兩者的差異。這個特性十分重要，我們因此用發現者來命名

it a law. Weber’s Law says that we perceive differences on a logarithmic, not a linear scale.

該項定律。韋伯定律描述我們能否分辨差異呈對數曲線，而非線性曲線。

It’s not the amount of change. It’s the percentage change that matters.

不是由改變的值的大小決定，而是由改變程度的百分比所決定

Alright. How about now we take a more in depth look at how one of our most powerful senses works?

好的，要不要現在就來更深入的討論我們最為強大的感覺能力?

Vision. Your ability to see your face in the mirror is the result of a long but

視覺。你之所以能在鏡中看見自己的臉是由於一長串但瞬忽即逝的事件結果

lightning quick sequence of events. Light bounces off your face and then off the mirror

光波從你的臉彈開接著落在鏡子上並反射

and then into your eyes, which take in all that varied energy and transforms it into

最後進到你的眼中，眼睛吸收不同波長的能量束並將它轉換成

neural messages that your brain processes and organizes into what you actually see,

神經訊號傳遞到腦中，由腦統整成你看見的一切

which is your face. Or if you’re looking elsewhere, you could see a coffee cup or a

也就是你的臉。或者假設你看向他處，你可以看見一個咖啡杯

Corgi or a scary clown holding a tiny cream pie.

或者一隻柯基或者一個嚇人的小丑端著一碟奶油派

So how do we transform light waves into meaningful information? Well, let’s start with the light itself.

那麼我們是如何將光波轉換成可被解讀的資訊呢? 讓我們從光本身講起吧

What we humans see as light is only a small fraction of the full spectrum

我們人類所見只是所有電磁輻射波長中的一小片段而已

of electromagnetic radiation that ranges from gamma to radio waves. Now light has all kinds

(電磁輻射波長範圍包括伽瑪射線到無線電波) ，光波有許多

of fascinating characteristics that determine how we sense it, but for the purposes of this topic,

有趣的特性，這些特性影響我們如何感測到它。回歸正題

we’ll understand light as traveling in waves. The wave’s wavelength and frequency

我們知道光是以波的形式傳遞，光的波長和頻率

determines their hue, and their amplitude determines their intensity or brightness.

決定了它的顏色，而振幅則決定它的強度和亮度

For instance a short wave has a high frequency. Our eyes register short wavelengths with high

舉例而言短波具有高頻率。在我們眼中高頻率的短波偏藍

frequencies as blueish colors while we see long, low frequency wavelengths as reddish hues.

而低頻率的長波則偏紅

The way we register the brightness of a color, the contrast between the orange of

我們所看見的光的亮度，雪寶冰的橘色和三角錐的橘色之間的差異

a sherbet and the orange of a construction cone has to do with the intensity or amount

取決於光波的強度以及其中帶有的能量

of energy in a given light wave. Which as we’ve just said is determined by its amplitude.

而我們在先前提過，光的強度和亮度由振幅決定

Greater amplitude means higher intensity, means brighter color.

振幅越大表示強度越高，顏色越亮

Someone’s just told me that sherbet doesn’t- isn’t a word that exists. His name is Michael Aranda

某人告訴我"雪酪"並不是一個真正存在的字彙，那人名叫 Michael Aranda

and he’s a dumbhead. Did you type it into the dictionary? Type it into Google.

他是個呆瓜。你有試著查過字典嗎? 不然問問google吧

Ask Google about sherbet. So sherbet is a thing.

在google查詢雪酪(sherbet)，雪酪是真正存在的

So after taking this light in through the cornea and the pupil, it hits the transparent

回歸正題，光波穿過角膜以及瞳孔後，它來到

disc behind the pupil: the lens, which focuses the light rays into specific images, and just

瞳孔後方透明的晶狀體，就像透鏡一般它將光束集中在一起

as you’d expect the lens to do, it projects these images onto the retina, the inner surface

然後就如你所熟知的透鏡功能，它把這些光投射在視網膜上，位於

of the eyeball that contains all the receptor cells that begin sensing that visual information.

眼球的內側表層，上面有許多負責接受視覺訊息的光受體細胞

Now your retinas don’t receive a full image like a movie being projected onto a screen.

目前你的視網膜並沒有接收到完整的、好比投影在螢幕上的電影一樣的影像

It’s more like a bunch of pixel points of light energy that millions of receptors translate

它比較像是一大堆光學像素，等著被光受體轉換成

into neural impulses and zip back into the brain.

神經衝動，然後一路送到腦部

These retinal receptors are called rods and cones. Our rods detect gray scale and are

視網膜上的光受體稱為桿細胞與錐細胞。桿細胞偵測灰階並

used in our peripheral vision as well as to avoid stubbing our toes in twilight conditions

參與周邊視野成像以及讓我們免於在黯淡光源下踢到腳趾

when we can’t really see in color. Our cones detect fine detail and color.

(特別是光源不足以讓我們看見色彩時)。我們的錐細胞負責完善細節並偵測顏色

Concentrated near the retina’s central focal point called the fovea, cones function only in well lit conditions,

它們集中在視網膜的中心焦點處稱為中央窩(中心小凹)，錐細胞只能在光源足夠時運作

allowing you to appreciate the intricacies of your grandma’s china pattern

讓你能欣賞你祖母的瓷器上的美麗花紋

or your uncle’s sleeve tattoo. And the human eye is terrific at seeing color. Our difference

或者你叔叔手背上的刺青。人類的眼睛非常精於分辨顏色，我們的色彩差異閾值

threshold for colors is so exceptional that the average person can distinguish a million different hues.

非常靈敏，這使得常人可以分辨出一百萬種不同色彩

There’s a good deal of ongoing research around exactly how our color vision works.

有許多關於人類彩色視覺的研究正在進行當中

But two theories help us explain some of what we know. One model, called the Young-Helmholtz

目前有兩個理論能幫助我們解釋我們已知的現象。其一，稱為 Young-Helmholtz

trichromatic theory suggests that the retina houses three specific color receptor cones

的三色視覺理論，該理論描述視網膜上有三種不同的錐細胞負責接收不同波長(顏色)的光

that register red, green and blue, and when stimulated together, their combined power

分別為紅、綠以及藍三種，而當它們一起作用，就能讓眼睛看見

allows the eye to register any color. Unless, of course you’re colorblind. About one in

各種顏色。除非你患有色盲，大約有五十分之一的人

fifty people have some level of color vision deficiency. They’re mostly dudes because

患有程度不一的彩色視覺缺失，大多數患者都是男性

the genetic defect is sex linked. If you can’t see the Crash Course logo pop out at you in this figure,

因為有缺陷的基因位在性染色體上。如果你無法看見這張圖上的Crash Course圖案

it’s likely that your red or green cones are missing or malfunctioning

那你可能缺少紅色或綠色錐細胞，又或者它們失常了

which means you have dichromatic instead of trichromatic vision and can’t distinguish

這表示你具有雙色視覺而不是三色視覺，而且無法分辨

between shades of red and green.

紅色以及綠色

The other model for color vision, known as the opponent-process theory, suggests that

另一個關於彩色視覺的理論，稱為互補處理理論，該理論描述

we see color through processes that actually work against each other. So some receptor

我們能看見色彩是透過一種色彩之間互相拮抗的方式。所以有些受體細胞

cells might be stimulated by red but inhibited by green, while others do the opposite,

會對紅光有反應但被綠光所抑制，反之亦然

and those combinations allow us to register colors.

這些不同的組合使得我們能看見色彩

But back to your eyeballs. When stimulated, the rods and cones trigger chemical changes

現在回到你的眼球，感應到光波時，桿細胞和錐細胞內會發生化學變化

that spark neural signals which in turn activate the cells behind them called bipolar cells,

並激發神經訊號，然後活化位於後方的細胞，稱為雙極細胞

whose job it is to turn on the neighboring ganglion cells. The long axon tails of these

該細胞負責活化周邊的神經節細胞，多個神經節細胞細長的軸突尾部

ganglions braid together to form the ropy optic nerve, which is what carries the neural impulses

匯集在一起成為視神經。而神經衝動便是由視神經

from the eyeball to the brain. That visual information then slips through a chain

傳達到腦部。視覺資訊在視神經中經過一連串

of progressively complex levels as it travels from optic nerve, to the thalamus,

漸進複雜的過程到達丘腦

and on to the brain’s visual cortex. The visual cortex sits at the back of the brain in the occipital lobe,

再傳遞至位於腦部後側枕葉的視覺皮質

where the right cortex processes input from the left eye and vice versa.

右側視覺皮質接收的神經訊息來自左眼，反之亦然

This cortex has specialized nerve cells, called feature detectors that respond to specific features

視覺皮質上具有特化的神經細胞，稱為形態偵測細胞，會對特定型態產生反應

like shapes, angles and movements. In other words different parts of your visual

像是形狀、角度以及移動。換而言之你的視覺皮質中不同的部位

cortex are responsible for identifying different aspects of things.

負責辨識事物的各種型態

A person who can’t recognize human faces may have no trouble picking out their set

一個無法辨識自己臉部的人卻毫無困難的在桌上的雜物堆中

of keys from a pile on the counter. That’s because the brains object perception occurs

找到自己的鑰匙。這是因為物體辨識功能位於腦部中

in a different place from its face perception. In the case of Dr. Sacks, his condition affects

不同位置。在 Sacks博士的症狀中，異常的部位

the region of the brain called the fusiform gyrus, which activates in response to seeing faces.

是腦中的梭狀迴，梭狀迴在看見臉時會產生反應

Sacks’s face blindness is congenital, but it may also be acquired through disease

Sacks’s的臉盲症是先天性的，但該症狀也可能因為疾病

or injury to that same region of the brain. And some cells in a region may respond to

或者因為腦中相同的部位受損而得到。特定腦區中的細胞可能

just one type of stimulus, like posture or movement or facial expression,

只對特定一種刺激有所反應，像是姿勢或者移動或者臉部表情

while other clusters of cells weave all that separate information together in an instant analysis of a situation.

而其餘的細胞則負責將這些型態訊息在事件當下完成分析並組合在一起

That clown is frowning and running at me with a tiny cream pie.

眼前正有個小丑手中拿著奶油派面帶不善的追著我

I’m putting these factors together. Maybe I should get out of here.

我將這些訊息湊在一起，得到結論也許我該快跑

This ability to process and analyze many separate aspects of the situation at once is called parallel processing.

可以分析並處理事物的不同型態與位置的能力稱之為平行處理

In the case of visual processing, this means that the brain simultaneously

在視覺辨識的例子中，腦部同時地

works on making sense of form, depth, motion and color and this is where we enter the whole

對形狀、深度、動作以及顏色進行分析，而這形成了我們

world of perception which gets complicated quickly, and can even get downright philosophical.

對於周遭環境的認知。但這類議題深入討論下去可能會變成哲學討論

So we’ll be exploring that in depth next time but for now, if you were paying attention,

所以我們將把更深入的部分放在之後再做討論。至於現在，如果你有專心聽

you learned the difference between sensation and perception, the different thresholds that

你已經知道感覺和知覺之間的不同、我們的感官受限於差異閾值

limit our senses, and some of the neurology and biology and psychology of human vision.

以及一些關於視覺的神經學、生物學和生理學知識

Thanks for watching this lesson with your eyeballs, and thanks to our generous co-sponsors

感謝收看這集眼球相關課程，同時感謝我們慷慨的贊助者們

who made this episode possible: Alberto Costa, Alpna Agrawal PhD, Frank Zegler, Philipp Dettmer and Kurzgesagt.

沒有他們就沒有這集節目：Alberto Costa, Alpna Agrawal PhD, Frank Zegler, Philipp Dettmer and Kurzgesagt.

And if you’d like to sponsor an episode and get your own shout out, you can learn

同時如果你有興趣贊助並且發表自己的評論

about that and other perks available to our Subbable subscribers, just go to subbable.com/crashcourse.

你可以試著到Subbable訂閱者的小額贊助看看，快點進 subbable.com/crashcourse.

This episode was written by Kathleen Yale, edited by Blake de Pastino, and our consultant

本集節目腳本由Kathleen Yale 編寫 ，Blake de Pastino 編輯， Ranjit Bhagwat博士顧問

is Dr. Ranjit Bhagwat. Our director and editor is Nicholas Jenkins, the script supervisor

Nicholas Jenkins 製作和執導 ，Michael Aranda 監製同時也是音樂設計

is Michael Aranda who is also our sound designer, and our graphics team is Thought Cafe.

最後我們的美術團隊是Thought Cafe