Why do we see illusions? - Mark Changizi

Translator: Andrea McDonough Reviewer: Bedirhan Cinar

翻译人员: Yinglei Li 校对人员: Geoff Chen

Why do we see illusions?

人为什么会有错觉？

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

让我来通过调查中

where I provided evidence for a different kind of hypothesis

获得的一些证据

来证明一项假设

than the one that might be in the book

这项假设

on your coffee stand.

完全不同于你在枕边书中读到的

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

好了，我们来看看这张错觉图

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

许多错觉图都能用这项假设来解释原因

that are explained by this hypothesis.

这张图是其中的代表

所以我将以此图为例做详细说明

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

As usual in these things,

如图所示

两条线实际上相互平行

these two lines are, in fact, parallel,

but you perceive them to bow outwards at their centers.

但你的感觉是它们的中间部分向外弯曲

At the center where those radial lines are,

在你的视野中

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

有射线穿过的中间部分

比上下两头都宽

太不可思议了

And this is remarkable,

because it's a remarkably simple stimulus.

其实它给你的刺激非常简单

It's just a bunch of straight lines.

因为它们只是些直线而已

Why should one of the most complicated objects in the universe

为什么宇宙中结构最复杂的人

无法辨识这幅简单至极的图像？

be unable to render this incredibly simple image?

要回答这个问题

When you want to answer questions like this,

you need to ask,

我们首先要问

“我的大脑看到了什么？”

well, what might this mean to your brain?

And what your brain is going to think this is,

这幅图对于大脑来说

is not some lines on a page.

绝不仅仅是一些线条而已

Your brain has evolved to handle the kinds of natural stimuli

人脑经过进化

已经能处理现实生活中遇到的

that it encounters in real life.

一些自然刺激

So when does the brain encounter stimuli like this?

那么当大脑遇到此类刺激时，会如何反应呢？

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

虽然它看上去有些奇怪

但实际上你一直都在经历这种刺激

you've been encountering this stimulus all day long.

Whenever you move,

只要你在移动

whenever you move forward, in particular.

特别是向前移动时

When you move forward, you get optic flow,

你会获得视觉流

景象在你的视野中向外扩张

flowing outwards in your visual field,

like when the Enterprise goes into warp.

就像进取号开始曲速飞行一样

All of these objects flow outwards

一切物体都在向外扩张

它们在你的视网膜上留下轨迹或残影

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

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

不断刺激着你的迷你神经元

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

以上是你在日常生活中遇到的一个例子

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

下面还有另一个一直遇到的刺激图像

In fact, cartoonists know about this.

漫画家十分了解这种刺激

They put these blur lines in their cartoons

他们把残影运用到漫画中

你看到时，大脑的反应就是运动

and it means to your brain: motion.

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

重点并非你看到的残影

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

而是你眼睛后部受到的刺激

that has these optic blurs in them,

眼睛接收到这些视觉残影后

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

大脑就做出了“你在移动”的反应

When you move forward, your eyes fixate like cameras,

当你向前移动时 眼睛就像自动照相机一样

like snapshot cameras,

捕捉图像

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

眼睛不停地

捕捉图像

就像相机在拍摄

每次你在前进时

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

捕捉图像

就会看到景象向外扩张

you get all this flowing outwards.

So when you take a fixation,

你捕捉到图像后

you end up with this weird optic blur stuff,

它会留下怪异的视觉残影

and it tells you the direction you're moving.

残影让你知道了自己移动的方向

Alright, that's half the story.

好了，以上并非对错觉的全部解释

That's what this stimulus means.

只不过告诉你什么是刺激

在第一次看到这幅图时

It means that your brain thinks,

when it's looking at the first image,

你的大脑做出了什么反应

还有，你实际上正在朝

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

图像中部移动

It still doesn't explain

然而，你还是不知道

why you should perceive these straight lines as bowed outwards.

为什么自己会感觉直线向外弯曲

To understand the rest of the story,

要回答这个问题

you have to understand that our brains are slow.

你得知道，我们的大脑不够快

也许你以为当光照进眼睛

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

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

“唰”地一下

就看到了

of what the world is like.

世界的面貌

事实上并非如此

But it doesn't work that way.

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

大脑要花十分之一秒的时间

来形成图像

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

十分之一听上去不长

但对普通行为来说不短

but it's a long time in normal behaviors.

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

假设你每秒移动一米

这速度很慢

那十分之一秒你就移动了10厘米

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

So if you didn't correct for this delay,

所以如果不修正这种延迟

那么在你感知到

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

任何身边10厘米范围内的东西时

by the time you perceived it,

你就已经

you would have bumped into it or just passed it.

撞上或直接错过它了

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

而且还有更糟的情况

(Laughter)

更糟的情况

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

就是

Your perception is behind.

自己的感知有延后

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

你希望自己

You want your perceptions at any time T

在“t”时间获得感知

to be of the world at time T.

此时外部时间也为“t”

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

要想让大脑做到这点

它必须要在光照到视网膜时

instead of generating a perception of the way the world was

给出更出色的反应

when light hit your retina,

而不是对外部世界

it has to do something fancier.

做实际反馈

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

大脑不能被动地对外界作出反应

而要最准确地预估 下个时点会发生什么

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

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

世界在十分之一秒后会怎么样？

Build a perception of that,

大脑会先对此作出描绘

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

因为

当大脑感知到未来时

the near future will have arrived

未来已经发生

and you'll have a perception of the present,

这样你就会得到一个对现在的感知

这是你希望大脑做到的

which is what you want.

In my research,

在我和其他领域的调查中

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

有大量证据表明

that have provided evidence --

大脑中充满了这类机制

that the brain is filled with mechanisms

以弥补自身反应速度上的缺失

that try to compensate for its slowness.

许多错觉都可以用 大脑的这种机制来解释

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

this just being one example.

这幅图只是个例子

But let me finish by saying,

但最后我还是想说明

大脑机制如何来解释这幅错觉图

how exactly does this explain this particular example?

So, the question, really, we have to ask

因此，我们的问题就变为

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

第一眼看到的两条竖直线

how do they change in the next moment

在下一刻将如何变化

were I moving towards the center,

如果我向中部移动

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

因为在视觉上 这些线条让我觉得自己在移动

What happens to them?

两条直线会怎么样？

Well, let's imagine.

好了，我们来看另一种情形

想象你面前有一扇门

Imagine you've got a doorway.

这是一扇

You've got a doorway.

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

大教堂的门

形象越具体

it'll be helpful in a second.

对我们接下去的说明越有帮助

你在远处看着门时

When you're very far away from it,

the sides are perfectly parallel.

门框完全平行

想象自己向门靠近

But now imagine what happens when you get closer.

It all flows outwards in your visual field,

当你靠得很近

在你的视野中门框会向外凸

flowing outwards.

越靠近变形越厉害

But when you're really close --

如果你靠得非常非常近

门框就在你两边时

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,

你抬头看大教堂的门

同时两手像这样向上移

the sides of the doorway are going up,

你会发现门框

like railroad tracks in the sky.

像两条轨道一样直指天空

What started off as two parallel lines,

一开始，门框是两条平行线

in fact, bows outwards at eye level,

而在视平面上向外突出

and doesn't go outwards nearly as much above.

到顶部又没有变形

So in the next moment,

于是下一刻

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

你脑中就形成了 如下幅图所示的图形

这牵涉到投影几何学

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

在下一时刻

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

事物本来的投影方式发生了改变

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

因此如果你接收到这样的刺激

对大脑来说

there's just two vertical lines

毫无疑问这只是两条竖直线

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

没有任何线索显示

它们接下去会发生变化

大脑就不会对图像进行加工

so just render it as it is.

But if you add cues --

但如果有附加线索

and this is just one of many kinds of cues

只要有一条

that can lead to these kinds of illusions,

可以导致错觉的线

this very strong optic blur cue --

比如上面提到的明显光学残影

你就能感知到

then you're going to perceive instead

下一刻将看到什么

exactly how it will appear in the next moment.

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

我们总试图感知现在

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

而实际上我们感知的是未来

而不是现在

And these illusions are failed perceptions of the future,

错觉其实是对未来的错误感知

because they're just static images on the page,

仅仅是脑中的静态图

they're not changing like in real life.

并没有真的发生变化

最后，我想用一幅错觉图来收尾

And let me just end by showing one illusion here.

If I can, I'll quickly show two.

如果时间允许就再加一幅

This one's fun.

这张图很有意思

If you just fixate at the middle there,

如果你盯着中间那点

and make stabbing motions with your head,

前后摆动你的头

looming towards it like this.

就像这样

Everybody do that.

大家一起来

Make short, stabbing motions.

快速摆动头

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

由于我在视觉流动方向加入了残影

你的大脑会想：“它们是残影

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

that's why they're blurry."

所以它们应该在移动”

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

你在摆动头的同时

视野中的图像会比实际动得更快

faster than they should.

它们本来没有这么快

They shouldn't be moving that much.

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

这是最后一幅图

这些是运动的线索

Here are the cues of motion,

事物移动时

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

会在视网膜上留下这样的线索

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

不做别的

你只要看着它就会有错觉

看到它们在移动的

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

举起你们的手

It's weird, right?

是不是很奇怪？

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

但你的大脑

接收到了线索

而你的眼睛

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

受到刺激

感觉“它们在移动”

这是对它们下一刻状态的感知

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

下一刻，它们应该在动

they should be moving and they should have shifted.

不停地移动

好了，谢谢大家

Alright, thank you very much.

(Applause)