Why do we see illusions? - Mark Changizi

Translator: Andrea McDonough Reviewer: Bedirhan Cinar

譯者: Jephian Lin 審譯者: Coco Shen

Why do we see illusions?

我們是怎麼產生錯覺的？

I'm going to tell you about some of my research,

我想談談我的研究，

where I provided evidence for a different kind of hypothesis

我為一些不一樣的假設

提出證據。

than the one that might be in the book

這些假設可能和你們

on your coffee stand.

在路邊找到的書裡說的不同。

Alright, so let's look at one of the illusions here.

好，讓我們先來看其中一種錯覺。

And this is a stand-in for many, many kinds of illusions

它是許多種錯覺的代表，

that are explained by this hypothesis.

那些錯覺都可以用這假設解釋。

我只是想要用這一個 來談一下這個假設。

I'm just going to walk through it for this particular one.

As usual in these things,

就像平常一樣，

這兩條線實際上是平行的，

these two lines are, in fact, parallel,

but you perceive them to bow outwards at their centers.

但是你覺得它們中間有向外微彎。

At the center where those radial lines are,

在你視覺中，那個輻射狀的中心，

it's wider in your visual field than the parts above and below.

比上面和下面的部份

都還要寬。

這很特別，

And this is remarkable,

because it's a remarkably simple stimulus.

因為它是特別簡單的圖形。

It's just a bunch of straight lines.

它只是一束直線而已。

Why should one of the most complicated objects in the universe

為什麼這宇宙中堪稱最複雜的器官

沒辦法處理這簡單到不行的影像？

be unable to render this incredibly simple image?

當你想要回答像這類的問題時，

When you want to answer questions like this,

you need to ask,

你必須去問：

「嗯，那這在我們腦中代表什麼呢？」

well, what might this mean to your brain?

And what your brain is going to think this is,

而我們大腦對它的想法

is not some lines on a page.

並不只是紙上的一堆線，

Your brain has evolved to handle the kinds of natural stimuli

你的大腦已經進化到

可以處理在現實生活中

that it encounters in real life.

會遇到的各種視覺刺激。

So when does the brain encounter stimuli like this?

所以什麼時候大腦 會遇到這種視覺刺激？

Well, it seems a bit odd, but in fact,

嗯，好像有點怪，

但事實上， 你每天都會遇到這種視覺刺激。

you've been encountering this stimulus all day long.

Whenever you move,

每當你移動的時候，

whenever you move forward, in particular.

尤其是每當你向前移動的時候。

When you move forward, you get optic flow,

當你向前移動時， 你會感覺視覺的流動，

在你的視覺影像中 向外流動，

flowing outwards in your visual field,

like when the Enterprise goes into warp.

就像是企業號啟動了曲速引擎一樣。 （譯註：企業號是影集星際迷航記的一艘太空船。）

All of these objects flow outwards

所有東西都向外流，

而它們在你的視網膜上 留下軌跡或是模糊的線。

and they leave trails, or blur lines, on your retina.

They're activating mini-neurons all in a row.

它們會啟動一整排的微小神經元。

So, this is a version of what happens in real life

所以，這是現實會發生的一個版本

and this another version of what happens in real life all the time.

而這也是常會發生的另一個版本。

In fact, cartoonists know about this.

事實上，漫畫家知道這點。

They put these blur lines in their cartoons

他們在他們的漫畫中加上模糊的線

而這在你的有腦中代表 ── 運動。

and it means to your brain: motion.

Now, it's not that in real life you see blur lines.

我並不是想說 你在現實生活中

The point is that it's the stimulus at the back of your eye

會看到模糊的線， 重點在於這個視覺刺激

that has these optic blurs in them,

會在你眼睛底層留下 模糊的圖像，

and that's what tells your brain that you're moving.

而就是它告訴你 你正在移動。

When you move forward, your eyes fixate like cameras,

當你向前走的時候， 你的眼睛會像相機一樣留下影像

like snapshot cameras,

像快照相機一樣，

it fixates, it fixates, little (Snapshot sound) camera shots,

它會留下影像、

留下影像、

一張張的小照片，

每一次它留下影像，

and each time it fixates when you're moving forward,

當你向前進時，

你會看到全部都向外流。

you get all this flowing outwards.

So when you take a fixation,

所以當你將底片定影的時候，

you end up with this weird optic blur stuff,

你會看到這奇怪的視覺模糊

and it tells you the direction you're moving.

而它會告訴你 你移動的方向。

Alright, that's half the story.

好，這是我要講的一部份。

That's what this stimulus means.

這是這個視覺刺激 代表的意義。

這表示你的大腦

It means that your brain thinks,

when it's looking at the first image,

在你看到第一張圖像時

會覺得你正在路上，

that you're actually on your way, moving towards the center.

正向中心點前進。

It still doesn't explain

但這還是沒有解釋為什麼

why you should perceive these straight lines as bowed outwards.

你會感覺那兩條線向外彎曲。

To understand the rest of the story,

要了解剩下的故事，

you have to understand that our brains are slow.

你必須知道我們的大腦運作緩慢。

你可能希望 光一接觸你的眼睛，

What you would like is that when light hits your eye,

then -- ping! -- immediately you have a perception

隨即，砰！

瞬間你就有整個世界

of what the world is like.

的視覺影像。

但大腦並不是這樣的。

But it doesn't work that way.

It takes about a tenth of a second for your perception to be created.

它大約須要十分之一秒

來產生視覺。

And a tenth of a second doesn't sound very long,

這十分之一秒聽起來並不太長，

但對一般的動作來說 它算是長的。

but it's a long time in normal behaviors.

If you're moving just at one meter per second, which is fairly slow,

如果你每秒動一公尺，

這算是很慢的，

那麼十分之一秒你已經走了十公分了。

then in a tenth of second, you've moved 10 centimeters.

So if you didn't correct for this delay,

所以如果你沒有修正這個延遲現象，

那麼每一樣你覺得

then anything that you perceived to be within 10 centimeters of you,

和你差十公分的物體，

by the time you perceived it,

在你看到的那一刻

you would have bumped into it or just passed it.

你可能就已經撞到或錯過它了。

And of course, this is going to be much worse --

而當然地，這可能會更糟，

(Laughter)

像是這種情況下，

it's going to be much worse in a situation like this.

可能會更糟。

Your perception is behind.

你的視覺慢了。

What you want is that your perception should look like this.

你期望看到的的應該是像這樣子。

You want your perceptions at any time T

你希望你在時間 t 看到的

to be of the world at time T.

應該是時間 t 的世界。

But the only way your brain can do that, is that it has to,

除了在光打到你的視網膜上時

大腦就馬上產生影像，

instead of generating a perception of the way the world was

這個方法外，

when light hit your retina,

你的大腦唯一可以做的

it has to do something fancier.

應該是更具想像力。

It can't passively respond and create a best guess,

我們不應該只是 消極地反應並做出猜測，

應該是要對下一刻做出最合理的猜測。

it has to create a best guess about the next moment.

What will the world look like in a tenth of a second?

十分之一秒之後的世界會像是什麼樣子？

Build a perception of that,

必須建立這樣的視覺影像，

because by the time your perception of the near future occurs in your brain,

因為當你的大腦建構好

這樣不遠的未來影像時，

the near future will have arrived

那這不遠的未來 就已經到了

and you'll have a perception of the present,

而你就變成有了 「現在」的影像，

這正是你想要的。

which is what you want.

In my research,

在我的研究中， 我為這想法提出證據，

I provided a lot of evidence -- and there's other research areas

也有其它研究提出證據，

that have provided evidence --

證明大腦擁有這類的機制

that the brain is filled with mechanisms

來彌補這樣的延遲。

that try to compensate for its slowness.

而我也證明了非常多的錯覺 都可以用這個來解釋，

And I've shown that huge swaths of illusions are explained by this,

this just being one example.

這只是一個例子而已。

But let me finish by saying,

但讓我說一下

這個想法要如何解釋 現在這個例子。

how exactly does this explain this particular example?

So, the question, really, we have to ask

所以，我們真正想問的是

is: how do those two vertical lines in that first stimulus,

第一張圖像中的兩條線，

how do they change in the next moment

這兩條線下一刻會是什麼樣子？

were I moving towards the center,

假設在我正在往中心點移動，

that all those optical lines are suggesting that I'm moving.

因為每條線都這麼跟我說，

What happens to them?

這情況下它們會怎麼改變？

Well, let's imagine.

那，讓我們想像看看。

想像前方有一扇門。

Imagine you've got a doorway.

有一扇門，

You've got a doorway.

Imagine it's a cathedral doorway, to make it more concrete --

想像那是教堂的大門，

這樣會具體些，

it'll be helpful in a second.

也會比較有用。

當你離它還很遠時，

When you're very far away from it,

the sides are perfectly parallel.

它的兩側是完全平行的。

但是想像當你靠近的時候。

But now imagine what happens when you get closer.

It all flows outwards in your visual field,

當你真的很靠近時，

在你的視覺中 它會向外流動

flowing outwards.

向外流，

But when you're really close --

但因為你是真的很靠近，

想像門的兩側就在這裡和這裡，

imagine the sides of the doorway are here and here,

but if you look up at this cathedral doorway and do your fingers like this,

但如果你看看教堂的大門

你會像這樣用手指來指它，

the sides of the doorway are going up,

門的兩側向上攀升

like railroad tracks in the sky.

就像鐵路到達天際。

What started off as two parallel lines,

原本平行的兩條線

in fact, bows outwards at eye level,

實際上會在眼睛水平處 向外彎曲

and doesn't go outwards nearly as much above.

而在上面的部份則 沒有那麼向外彎。

So in the next moment,

所以在下一刻，

you have a shape that's more like this next picture.

你會看到的形狀 更像這下一張。

這實際上，就是投影幾何，

The projective geometry -- that is, the way the things project,

有一種投影會讓

in fact, change in this way in the next moment.

影像在下一刻變成這樣。

So when you have a stimulus like this, well, your brain has no problem,

當你遇到這樣的視覺刺激，

你的大腦不會有什麼問題，

there's just two vertical lines

它們就只是兩條垂直的線，

and no cues that there'll be a change in the next moment,

因為沒有提示

告訴你下一刻會有改變，

所以只要正常地處理它就好。

so just render it as it is.

But if you add cues --

但如果加了些提示，

and this is just one of many kinds of cues

這只許多會造成這類錯覺

that can lead to these kinds of illusions,

的提示之一，

this very strong optic blur cue --

這個非常強烈 視覺模糊的提示，

那你會感受到的

then you're going to perceive instead

就剛好會是下一刻會顯現的樣子。

exactly how it will appear in the next moment.

All of our perceptions are always trying to be about the present,

我們所有的知覺， 都試著與現在相符，

but you have to perceive the future to, in fact, perceive the present.

但你必須感覺未來

才能實際地感覺現在。

And these illusions are failed perceptions of the future,

而這些錯覺則是 對未來失敗的預測，

because they're just static images on the page,

因為它們只是靜止的一張圖像，

they're not changing like in real life.

他們並不像現實中會動。

讓我用這一個錯覺做結尾，

And let me just end by showing one illusion here.

If I can, I'll quickly show two.

如果可以的話，看能不能講兩個。

This one's fun.

這個很有趣。

If you just fixate at the middle there,

如果你注視中間，那裡，

and make stabbing motions with your head,

然後前後移動你的頭，

looming towards it like this.

像這樣靠近它。

Everybody do that.

每個人都試試看。

Make short, stabbing motions.

試幾下前後移動。

Because I've added blur to these optic flow lines,

因為我有把這些視覺流線 變得模糊，

你的大腦會告訴你： 「它們可能已經在動了，

your brain says, "They're probably already moving,

that's why they're blurry."

所以才會變得模糊。」

When you do it, they should be bursting out in your visual field

當你這麼做的時候，它們就會

在你的視覺中向外炸， 超過它們應該有的速度。

faster than they should.

它們不應該移動那麼多。

They shouldn't be moving that much.

And a final one I'll just leave in the background is this.

而最後一張我會留下來當背景的 是這張。

這裡面有移動的線索，

Here are the cues of motion,

當你看到物體在動的時候， 會看到

the kinds of cues that you get on your retina when things are moving.

這類的線索。

You don't have to do anything -- just look at it.

你不用做什麼動作，

只要看著它就好。

可能有許多人，看到的請舉手，

Raise your hand if things are moving when they shouldn't be.

明明它們不該動 可是你感覺到東西在移動。

It's weird, right?

這很詭異，對吧？

But what you have now are the cues that, from your brain's point of view,

但你現在有的只是提示，

這來自你大腦的觀點、

你的眼睛，

you have the stimulus on your eyes, like, "Oh, these things are moving."

會有視覺刺激告訴你的眼睛：

「喔，這些東西在移動。」

產生它們下一刻 可能的視覺影像

Render a perception of what they'll do in the next moment --

在下一刻，他們可能會移動

they should be moving and they should have shifted.

或是會位移。

好，非常謝謝你們。

Alright, thank you very much.

(Applause)