第11讲 感知三维世界—深度知觉在线视频

现实世界是一个三维立体的世界
The real world is a three-dimensional world

我们的视觉感受器
Our visual receptors

也就是眼睛的视网膜只是一个平面
that is, the retinas of the eyes are just a plane

为什么还能把这个世界知觉为立体的呢
Why can we perceive the world as three-dimensional?

我们总能轻松辨别远近不同的物体
We can always easily distinguish between different objects in different distances

或者同一物体远近不同的部分
or different parts of the same object

也就是能产生深度知觉和立体视觉
That is to say we can have depth perception and stereoscopic vision

我们是怎么做到的呢
How do we do it?

实际上
In fact

眼睛要通过很多线索才能产生深度知觉
eyes can have deep perception using many clues

这些线索包括双眼线索和单眼线索
including binocular cues and monocular cues

双眼线索有两种
There are two kinds of binocular cues

第一种是视轴辐合
and the first is convergence of the optic axis

远处的物体与我们的双眼形成的夹角较小
The angle formed by the distant object and our two eyes is smaller

近处的物体与我们的双眼形成的夹角较大
and the angle formed by the near object and our two eyes is bigger

为了形成不同的夹角
In order to form different angles

眼睛周围的肌肉需要对眼睛进行不同的调节
the muscles around the eyes need to adjust the eyes differently

大脑利用眼部肌肉运动的信号
The brain uses the signals of eye muscle movement

来判断物体的距离
to judge the distance between the objects and us

这就是视轴辐合
This is the convergence of the optic axis

第二种双眼线索是双眼视差
The second kind of binocular cues is binocular parallax

我们有两只眼睛 中间相隔5到6厘米
We have two eyes, five to six centimeters apart

所以两只眼睛看到的物体并不完全相同
so the objects seen by the two eyes are not exactly the same

尤其是近处的物体
especially those not far from us

比如
For example

我用双眼看我眼前的手掌
I use my eyes to look at the hand in front of me

左眼看到的是手心
What I see in my left eye is the palm of my hand

右眼看到的是手背
and what I see in my right eye is the back of my hand

差别很大
They are quite different

如果一个物体很远
If an object is far away

那么双眼看到的物体就很相似
the objects seen by the two eyes are very similar

双眼看到的物体的图像差异大小
The size of difference between images seen by the two eyes

就提供了物体远近的信息
provides the information of distance

在物体距离较近的时候
When the object is close to us

距离的变化引起视角的变化比较大
the change of distance causes big change of visual angle

引起的双眼视差的变化也比较大
and big change of binocular parallax

所以能提供物体远近的信息
which can provide the information of distance

但物体比较远的时候
But when the object is far away

距离的变化引起
the change of distance causes very little change

视角和双眼视差的变化都很小
of visual angle and of binocular parallax

就无法提供有效的距离线索了
which can not provide effective distance cues

这时我们需要依赖单眼线索
At this point, we need to rely on monocular cues

第一种单眼线索是对象重叠
The first monocular cue is object interposition

在三维视觉世界中
In the three-dimensional visual world

当一个物体与另一个物体互相遮挡时
when one object and another object block each other

总是近的一个遮挡远的一个
the close one always block the further one

因此被遮挡的物体就被知觉为距离观察者更远
so the blocked one is perceived as further away from the observer

这就是对象重叠线索
This is object interposition cue

像这个图里边 我们就认为
In this picture, we think that

狗距离我们比较近
the dog is closer to us

而人距离我们比较远
while the person is far away from us

就是因为人被狗遮挡了
because the person is blocked by the dog

第二种线索是空气透视
The second cue is aerial perspective

在三维视野中
In the three-dimensional field of vision

远处的物体显得模糊
the objects in the distance are blurry

近处的物体显得清晰
and the objects close are clear

当我们看到视野中有的地方模糊
When we see that some objects in our vision are blurry

有的地方清晰
and some are clear

我们就把模糊的地方知觉为距离较远
we perceive the blurry ones as far away

把清晰的地方知觉为距离较近
and the clear ones as closer

第三种线索是相对大小
The third cue is relative size

在三维的视觉世界中
In the three-dimensional visual world

两个大小相等的物体
there are two objects of the same size

更靠近观察者的物体
and the objects closer to the observer

在我们视网膜上的成像更大
have larger image on our retina

所以如果我们知道两个物体本来是一样大的
so if we know that the two objects are the same size originally

但看上去其中一个较大
but one of them seems to be larger

那么较大的就被知觉为距离较近
then the larger one is perceived to be closer

这就是相对大小线索
This is the relative size clue

第四种线索是线条透视
The fourth clue is linear perspective

在三维的视觉世界中
In the three-dimensional visual world

两条向远方伸展的平行线看起来趋于接近
two parallel lines stretching to the distance seem to be closer and closer

所有 如果我们看到两条线平行
so if we see two lines parallel

就会觉得在视野中趋于接近的一端距离较远
we will think that the close end in the field of vision is far away

这就是线条透视线索
This is the linear perspective cue

第五种线索是纹理梯度
The fifth cue is texture gradient

在三维的视觉世界中
In the three-dimensional visual world

视野中的物体在视网膜上投影的大小
the size and density of the projection of objects in the field of vision

和密度会发生有层次的变化
on the retina will change hierarchically.

远处的物体在视网膜上的投影更小
The projection of distant objects on the retina is smaller

显得更密
and more dense

所以
Therefore

当我们看到视野中的纹理有的地方密
when we see the texture in the field of vision at some places are dense

有的地方疏
and at some places are sparse

我们就把纹理更密的地方视为距离我们较远
we regard the place with more dense texture as far away from us

我们成年人能自动识别视野中的深度和距离
Adults can automatically recognize the depth and distance in the field of vision

那么这种能力是天生的呢 还是后天习得的呢
Is this ability innate or acquired?

心理学家吉布森和沃克
Psychologists Gibson and Walk

设计了一个视崖实验
designed a visual cliff experiment

视崖是这样的
The cliff was like this

一张 1.2米高的桌子
a 1.2-meter-high table

顶部是一整块透明的厚玻璃
with a whole piece of transparent thick glass on the top

桌子的一半是用红白图案组成的结实桌面
Half of the table was a solid table top made up of red and white patterns

相当于浅侧
which was the shallow side

另一半是同样的图案
The other half was the same pattern

但它在玻璃下面的地板上
but it's on the floor under the glass

看上去很深
and it looked very deep

相当于深侧
which was the deep side

视崖高度是90cm
The height of the cliff was 90cm

在浅侧和深侧的中间
between the middle of the shallow side and the deep side

是一块0.3米宽的中间板
Is a 0.3m wide intermediate plate lied

被试是36名6个月到14个月的婴儿
The subjects were 36 infants aged 6 to 14 months

当把婴儿放在中间
When a baby was placed in the middle

妈妈在浅侧对面或者深侧对面
the mothers attracted their children with toys

用玩具吸引他们的孩子
on the opposite side of the shallow side or the opposite side of the deep side

发现36个婴儿中有27个
It was found that 27 of the 36 babies

爬过了浅侧到母亲身边
crawled over the shallow side to the mothers

而只有3名爬过深侧到母亲身边
while only 3 crawled over the deep side to the mothers

这说明
This showed that

婴儿能知觉到深度
babies can perceive depth

并认为深度意味着危险
and thought that depth means danger

在另外的实验中
In another experiment

当视崖调整到26cm时 38％的婴儿爬过了深侧
38% of the infants climbed over the deep side when the cliff was changed to 26 cm

说明视崖深度越大
The greater the depth of the cliff

婴儿拒绝越过的倾向就越强
the stronger the tendency of infants to refuse to cross it

婴儿的年龄越大
The older the infants were

爬过深侧的越少
the less they climbed over the deep side

说明年龄大的婴儿深度知觉更敏锐
indicating that the older infants were more acutely aware of depth

并且知道深度意味着危险
and knew that depth meant danger

那么 那些不会爬的婴儿能知觉到深度吗
So, can babies who could not crawl perceive the depth?

如果能知觉到深度 他们会感到恐惧吗
Would they be scared if they could feel the depth?

坎波斯等人把2-7个月的婴儿放在视崖边上
Campos et al. put 2-7-month-old babies on the edge of the cliff

并测量他们的心率
and measured their heart rate

结果发现
The results showed that

7个月的婴儿心率加快
the heart rate of 7-month-old babies increased

表明他们感到恐惧
indicating that they feared

而2个月的婴儿心率变慢
while the heart rate of 2-month-old babies slowed down

表明他们对新异性产生了兴趣
indicating that they were interested in novelt

但没有感到恐惧
but did not feel

这项实验说明
This experiment showed that

2个月的婴儿已经能知觉到深度
2-month-old babies had been able to perceive depth

但他们还没有学会爬行
but they had not yet learned to crawl

所以不知道深度意味着危险
so they did not know that depth meant danger

而7个的婴儿在学习爬行的过程中
while 7-month-old babies had learned

已经知道了深度意味着危险
that depth meant danger in the process of learning to crawl

好 今天的课就讲完了
OK, that’s all for today

现在回顾一下主要内容
Now let's review the main content

我们利用两类线索知觉深度
We use two types of cues to perceive depth

一类线索是双眼线索
One type of cue is binocular cues

包括视轴辐合和双眼视差
including visual axis convergence and binocular parallax

另一类是单眼线索
The other is monocular cues

包括对象重叠 空气透视 相对大小
including object interposition, aerial perspective, relative size

线条透视和纹理梯度
linear perspective and texture gradient

另外 2个月的婴儿已经能知觉到深度
In addition, 2-month-old infants have been able to perceive depth

但还不知道深度意味着危险
but do not know that depth means danger

而 7个月以上的婴儿不但能知觉到深度
while more than 7-month-old infants can not only perceive depth

还知道深度意味着危险
but also know that depth means danger

另外 我们在附加学习材料中
In addition, we have prepared the relevant contents of

还准备了大小知觉 时间知觉和错觉的有关内容
size perception, time perception and illusion in the additional learning materials

大家可以去学习
for you to learn

下次课我们将进入第4章意识
In the next lesson, we will turn to Chapter 4, consciousness

首先讲述
First, we will talk about

为什么我们有时能做出理性的判断
why we sometimes make rational judgments

有时却只能做出直觉的判断
sometimes only intuitive judgments

好 下次再见
OK, see you next time