【英语时差8，16】眼见

 Don: Say you're looking at an object on a table in front of you. How long do you think your eyeballs stay in one position?

Ya?l: You mean, how long before they move? I'm going to guess... a minute.

D: More like less than a second.

Y: Yow!

D: Though we feel as if our eyes stay completely still when we focus on something, researchers have found they only stay still at most for a couple seconds--often just a few milliseconds. What's fascinating about this is that every time our eyes move, we are momentarily visually impaired¹. We aren't seeing anything but a blur². So if we're always moving our eyeballs, and are always impaired, why don't we experience the world as a confusing rush?

Y: I bet you have an answer.

D: Researchers at the University of Delaware have a good guess. They have done studies that show the brain is always extending the boundaries of what it sees-- adding in made-up information along the edges. This process is called "boundary extension," and it seems to be going on all the time. Say you're looking at a brick wall. You really only see a small section of it, but your visual processing system essentially³ says, "I can assume that beyond my visual field on either side are more red bricks, so for now I'll just add them in until I get better information." That process of constantly extrapolating on what you see may be what allows you to experience a calm and consistent visual world, even though the actual data coming in is much more fragmented.  

1 impaired   

adj.受损的；出毛病的；有（身体或智力）缺陷的v.损害，削弱( impair的过去式和过去分词 )

参考例句：

• Much reading has impaired his vision. 大量读书损害了他的视力。 来自《现代汉英综合大词典》
• His hearing is somewhat impaired. 他的听觉已受到一定程度的损害。 来自《现代汉英综合大词典》

2 blur   

n.模糊不清的事物；vt.使模糊，使看不清楚

参考例句：

• The houses appeared as a blur in the mist.房子在薄雾中隐隐约约看不清。
• If you move your eyes and your head,the picture will blur.如果你的眼睛或头动了，图像就会变得模糊不清。

3 essentially   

adv.本质上，实质上，基本上

参考例句：

• Really great men are essentially modest.真正的伟人大都很谦虚。
• She is an essentially selfish person.她本质上是个自私自利的人。