英语听力文摘 English Digest 447、眼睛的“盲区”（在线收听）

人们都说“眼睛是心灵的窗户”——通过双眼,我们能看世间百态,能看人情冷暖,能看缤纷色彩……

        可大多数人并不知道,在视网膜的某一个地方,世界是黑白的,是没有色彩的.

        今天,让我们一起来学习有关视网膜的知识.了解眼睛的“盲区”……

The Green Door

Don: Here’s a simple demonstration you can do with cool implications. Find a large object that is brightly colored–let’s make it a green door.

Stand with that door to your side but don’t look directly at it; you want it to be in your peripheral vision. Now, without shifting your gaze, examine the door in the edge of your field of vision. What color is it? Answer? It’s still green.

Yael: It’s still green? What kind of experiment is that? I thought you are going to say something happens to the color.

D: That's exact right! The color stays green, which means something has happened – because nothing in your peripheral vision should have any color at all.

Y: Nothing in your peripheral vision should have any color? Why not?

D: Because color is what we perceive when light of a particular frequency meets cones–special cells in your retina. But the light being reflected off the door is only landing on the outside edge of your retina. And there are almost no cones on the edges. Everything we see roughly seventy-five degrees away from the point we’re fixed on should be black and white.

Y: That's fascinating! But why is the door still green?

D: Presumably the door remains green because vision isn’t a simple matter of retinal cells. All the data your eyes send is interpreted by the brain. Your brain knows that the door is green, so it supplies information that isn’t really there to keep the image stable.

This is just one of the many ways your brain saves time and energy by making reasonably safe assumptions about the world around you.

绿色的门

D: 告诉你一个很简单的论证：通过它你可以得出很酷的答案。找到一个大的颜色鲜艳的物件——将其视作一扇绿色的门。

靠着那扇门站定，但是不要直视它，只是把它纳入你的周边视野即可。现在，不改变凝视的方向，从你视野的最边缘仔细看看那扇门。它是什么颜色的？答案是什么？那扇门依然是绿色的。

Y: 还是绿色？这是个什么实验啊？我猜你接下来应该会讲讲，那扇门的颜色究竟发生了什么神奇的事情。

D: 当然！门保持绿色就意味着发生了什么改变——因为在周边视野范围内事没有什么颜色的。

Y: 周边视野范围内是没有颜色？为什么？

D: 因为，当特定波长的光线作用于视锥细胞（视网膜中的一种特殊的细胞）时我们所接收到的便是颜色。但是，从门上发射出来的光线仅能到达视网膜的外缘，在视网膜的外缘几乎没有视锥细胞。从我们所凝视的方向斜75度角所看到的所有东西都只能是黑白的。

Y: 太神奇了！可为什么门还是绿色的呢？

D: 门一直保持绿色大概是因为我们的视觉并不仅仅是视网膜细胞所能控制的吧。由眼睛传送的所有信息都是经过大脑编译的。大脑所给出的信息是：门是绿色的。因而，大脑传送出了并未遵循图像的信息。

为节省时间与精力，大脑对你周围的世界作出合理、安全的假设——而这仅仅是众多省时省力的方法之一。