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Most of the time, physical blindness is like a blindfold:
大多数时候，生理性失明就像蒙上了眼罩：
It keeps people from taking in visual signals at all.
它使人无法接受视觉信号。
But there's a surprising exception to that rule.
但这条规则有一个令人惊讶的例外。
In some rare cases, people can lose their vision but still respond to visual cues—except,
在一些罕见的情况下，人们可能会失去视力，但仍然会对视觉线索做出反应，
they do it subconsciously.
除非他们是下意识地这么做的。
In other words, they can see without knowing they're seeing.
换句话说，他们可能在不知道自己看的情况下却看到了。
This condition is called blindsight.
这种情况称为失明。
And not only does it shed light on how vision works, it also offers some clues to human consciousness.
它不仅揭示出视觉的工作方式，还为人类意识提供了一些线索。
The first person to observe blindsight was a grad student in the late 1960s who was working with a rhesus monkey named Helen.
第一个观察到失明的人是20世纪60年代末的一个研究生，和他一起工作的是一只名叫海伦的恒河猴。
Helen's primary visual area, known as V1, had been surgically removed so scientists could study that region's role in vision.
海伦的主要视觉区域，也就是V1，已经被手术切除，这样科学家们就可以研究该区域在视觉中的作用。
Generally speaking, whether you're a human or a monkey, damage to V1 makes you blind.
一般来说，无论是人类还是猴子，V1损坏都会造成失明。
And as far as anyone could tell, Helen could basically only tell apart light from dark.
据说，海伦基本上只能分辨光明和黑暗。
But!
但是！
The grad student noticed that if he held up a piece of fruit, Helen would look at it and reach to grab it.
这个研究生注意到，如果他举起一块水果，海伦就会看着它，然后伸手去抓。
She could also navigate through obstacles to eat crumbs off the floor.
她还可以穿过障碍物吃地板上的面包屑。
So, at times, she seemed to act like any monkey with typical eyesight.
所以有时候，它表现得像任何一只有着正常视力的猴子。
But other times, like when she got upset, she'd still stumble around like she couldn't see.
但其他时候，比如她心烦意乱时，她还是会像看不见一样蹒跚而行。
So in some ways, she was clearly blind.
所以在某些方面，她显然是个瞎子。
Of course, Helen couldn't tell anyone what her experience was like, so no one knew for sure what was going on—until a similar thing showed up in human patients.
当然，海伦不能告诉任何人她的经历，所以没人确切知道发生了什么，直到类似的事情出现在人类患者身上。
In one famous case, a patient known as DB had brain surgery that accidentally damaged one side of his vision center,
在一个著名的病例中，一位名叫DB的病人做了脑部手术后，意外地损坏了视觉中心的一侧，
so he could no longer see anything to the left of his nose.
他因此而再也看不到鼻子左边的东西了。
But, a researcher noticed DB would reach for things outside his field of view, as if he could actually see certain things in his blind spot.
但是，一位研究人员注意到DB会伸手去拿他视野之外的东西，好像他真能在盲点看到某些东西。
So a team of researchers came up with an unusual experiment.
因此，一组研究人员想出一个不同寻常的实验。
They would shine a circle of light into his blindspot, then ask DB to point at it.
他们会把一圈光照进他的盲点，然后让DB指向它。
And he'd say he couldn't.
他会说他做不到。
Cause he was blind.
因为他是瞎子。
But if they asked him to just guess, he was usually right.
但如果他们让他猜，他通常是对的。
The researchers also projected lines on a screen and asked DB to "guess" whether they were horizontal or vertical.
研究人员还将线条投射到屏幕上，让DB“猜”它们是水平的，还是垂直的。
And even though he assured them he couldn't see anything, he guessed right more than 80 percent of the time.
尽管他向他们保证他什么也看不见，但80%以上的时间里他都猜对了。
Which is way better than random chance.
这比随机的机会好得多。
And DB wasn't the only person with this apparent superpower.
DB并不是唯一拥有这种明显超能力的人。
Another patient named TN had his visual centers damaged from two separate strokes that left him completely blind.
另一位叫TN的病人，由于两次不同的中风导致他的视觉中枢受损，而完全失明。
But again, scientists suspected there was more to the story.
但是，科学家们再次怀疑这个故事还包含更多的内容。
On one occasion, they asked him to walk down a supposedly empty hallway —except, it wasn't empty.
有一次，他们让他走在一条据说空荡荡的走廊上——但是，那条走廊并不是空的。
The scientists had filled it with boxes, chairs, a file tray, and all sorts of obstacles.
科学家们在走廊里装满了箱子、椅子、文件盘和各种各样的障碍物。
But TN perfectly dodged every single one.
但TN完美地躲过了每样东西。
Except, afterward, he had no idea that the hallway was anything but empty.
不过，后来他完全不知道走廊并非空空荡荡。
So how on earth can people do this?
那么，人们究竟如何做到这一点呢？
Scientists have some ideas.
科学家们有一些想法。
First of all, in each of these patients, the same part of the brain was damaged: that V1 region that had been removed from Helen, the monkey.
首先，在这些病人中，大脑的同一部分受损：从猴子海伦体内移除的V1区。
Scientists think this region is where signals from your eye turn into conscious sight.
科学家认为，该区域是双睛的信号转变成有意识的视觉的地方。
But…
但是......
V1 is just one part of a complex network that gives us our vision.
V1只是复杂网络的一部分，这个复杂的网络为我们提供了视力。
See, when signals leave your retina and travel through the optic nerve, they don't go straight to V1.
看，当信号离开视网膜并通过视神经传递时，它们不会直接到达V1区。
Their first stop is a part of the brain called the thalamus, which is sort of like a relay center.
它们的第一站是大脑中称为丘脑的一部分，有点像中继中心。
From there, most visual signals go on to V1, but two other paths lead signals to different parts of the brain:
从那里，大多数视觉信号进入V1区，但另外两条路径将信号引导到大脑的不同部位：
the amygdala and a region called hMT+.
杏仁核和一个叫做hMT+的区域。
The amygdala is involved in emotional responses, like when you're scared.
杏仁核参与情绪反应，比如当你害怕的时候。
And it acts subconsciously.
表现为下意识地行动。
So, for example, you can react to something scary even before you consciously understand what you're reacting to.
所以，举例来说，你甚至可以在有意识地理解自己的反应之前，就对一些可怕的事情做出反应。
Like, if you open your apartment door and find a crowd of people inside, you might jump before realizing it's a surprise party.
比如，如果你打开公寓门，发现里面有一群人，你可能会在意识到这是一个惊喜派对之前跳起来。
In other words, even if the signals going to V1 hit a dead end because it's damaged, the amygdala is still getting visual signals— and responding to them—even when you're not consciously involved.
换句话说，即使去V1的信号因为受损而陷入死胡同，杏仁核仍会收到视觉信号，即使你没有意识到，它们也会做出反应。
HMT+ is another part of the vision system that tracks movement by picking up on things like change and contrast.
HMT+是视觉系统的另一部分，它通过捕捉变化和对比来跟踪运动。
It also gets signals from the thalamus, and scientists think people may be able to register where things are moving in their visual field,
它也能从丘脑得到信号，科学家们认为人们也许能在他们的视野中记录物体的运动，
even though it can't see the thing that's moving.
即使丘脑看不到运动的物体。
Those are two possible ways people might be able to see when they're blind.
当人们失明时，有两种可能的方式使人们看到事物。
But it is possible there are simpler explanations.
但是，也有可能存在更简单的解释。
For example, humans rarely have V1 completely damaged.
例如，人类很少出现V1区域完全受损的情况。
And, like DB, they usually have vision in at least part of their visual field.
而且，和DB一样，它们通常至少在部分视野中存在视觉。
So in some cases, maybe patients are able to make accurate guesses because of light scattering to the parts that can see.
所以在某些情况下，也许病人能做出准确的猜测，因为光散射到能看到的部分。
There are also some people with blindsight who report seeing…something.
也有一些失明的人报告说看到了一些东西。
Like waves or shadows.
比如波浪或阴影。
That might influence how they answer.
这可能会影响他们的回答。
But many patients are just as surprised by their abilities as the experimenters.
但是，许多病人和实验者一样，对他们的能力感到惊讶。
The idea of subconscious signals influencing people's behavior isn't new, though—we've known about unconscious perception for decades.
潜意识信号影响人们行为的想法并不新鲜，尽管我们对无意识感知的了解已经有几十年了。
Scientists have recorded many examples of people reacting to images or words that flashed in front of them too quickly to register consciously.
科学家们记录了许多人对眼前闪过的图像或文字，做出反应的例子。
But one of the interesting things about blindsight is it shows that our conscious experiences are just a small part of the work our brains actually do.
但是，关于失明的一件有趣的事情是，它表明我们的意识体验只是我们大脑实际工作的一小部分。
No one knows what makes us conscious, or why we experience life instead of just going through the motions like a robot.
没有人知道是什么让我们有意识，也不知道为什么我们享受生活，而不是像机器人一样行动。
But research on blindsight gives us an unusual window into this problem.
但是，对失明的研究给我们提供了一个研究这个问题的不同寻常的机会。
It shows us that certain brain regions seem to be responsible for our conscious experience of vision,
它向我们展示出大脑的某些区域，似乎掌管对于有意识的视觉体验，
and it also tells us that in a lot of ways, vision can work unconsciously—just a sequence of input and output.
它也告诉我们在很多方面，视觉可以无意识地工作，只是一系列的输入和输出。
Which brings up an unsettling question: If blind people unknowingly respond to things they don't see, what about people who can see?
这就引出了令人不安的问题：如果盲人在不知情的情况下，对他们看不到的东西做出反应，那么能看到的人呢？
Do they also respond to things they're not conscious of?
他们也会对自己意识不到的事情做出反应吗？
They almost certainly do.
几乎可以肯定是这样。
We all have unconscious processing going on all the time, but, fortunately, we don't usually need to rely on it.
我们都在无意识地处理一些事情，幸运的是我们通常不需要依赖它。
And while it might be a little creepy to think that your brain is nudging you along while you're blissfully unaware,
你在不知道自己喜悦时，认为大脑在劝说你，这可能有点令人毛骨悚然，
it's also reassuring to know it's looking out for you more than you think.
但它比你想象的更关心你，这也让人安心。
While it may seem odd to you that there are parts of your brain guiding you subconsciously,
虽然在你看来，你大脑的某些部分潜意识地引导着你，
the real mystery for scientists is why we have consciousness at all.
但你对科学家来说真正的谜团是我们为什么会意识到。
