TED演讲：拥有大脑的真正原因(4)

 　　So for example, if you put your hand under a table and try to localize it with your other hand, you can be off by several centimeters due to the noise in sensory¹ feedback.  比如说，如果把一只手放在桌子底下，然后在桌子上面用另一只手去对准，最后位置可能相差好几厘米，这就是因为感官回馈里面的杂音在起作用。

　　Similarly, when you put motor output on movement output, it's extremely noisy.  同样，运动神经输出的肌肉动作和实际输出之间也是有很多杂音的。

　　Forget about trying to hit the bull's eye in darts², just aim for the same spot over and over again.  且不谈扔飞镖的时候瞄准靶心去扔，只看重复瞄准同一点的时候发生什么情况。

　　You have a huge spread due to movement variability.  由于每次动作都有差异，最后瞄准的结果会形成一片散点。

　　And more than that, the outside world, or task, is both ambiguous and variable.  更何况外界环境和要执行的任务常常模糊和变化着的。

　　The teapot could be full, it could be empty.  看这个茶壶，可能是满的，也可能是空的。

　　It changes over time. So we work in a whole sensory movement task soup of noise. 每次都不一样。所以我们其实是随时处在一大堆感官动作杂音环绕之中做动作的。

　　Now this noise is so great that society places a huge premium³ on those of us who can reduce the consequences of noise.  这种杂音相当厉害，以至于我们社会会给那些能有效减少杂音带来的后果的人巨额奖赏。

　　So if you're lucky enough to be able to knock a small white ball into a hole several hundred yards away using a long metal stick,  所以在座哪位能做到像老虎伍兹那样，用一根长金属杆把一个小白球打进几百米开外的洞里，

　　our society will be willing to reward you with hundreds of millions of dollars. 我们的社会愿意奖励你百万千万的钱。

　　Now what I want to convince you of is the brain also goes through a lot of effort to reduce the negative consequences of this sort of noise and variability.  好，我接下来想说明的是其实我们的大脑为了减少噪音和变化性的负面影响，也做了很多工作。

　　And to do that, I'm going to tell you about a framework which is very popular in statistics and machine learning of the last 50 years called Bayesian decision theory.  为此，我来介绍一个在过去50年里统计学和机器学习方面都很常用到的架构，叫做贝叶斯决策论。

　　And it's more recently a unifying⁴ way to think about how the brain deals with uncertainty⁵.  近来这个理论常被用来从整体上理解大脑如何处理这种不确定性。

　　And the fundamental idea is you want to make inferences and then take actions. 基本思路是先做推断，然后做出动作。

1 sensory   

adj.知觉的，感觉的，知觉器官的

参考例句：

• Human powers of sensory discrimination are limited.人类感官分辨能力有限。
• The sensory system may undergo long-term adaptation in alien environments.感觉系统对陌生的环境可能经过长时期才能适应。

2 darts   

n.掷飞镖游戏；飞镖( dart的名词复数 )；急驰，飞奔v.投掷，投射( dart的第三人称单数 )；向前冲，飞奔

参考例句：

• His darts trophy takes pride of place on the mantelpiece. 他将掷镖奖杯放在壁炉顶上最显著的地方。 来自《简明英汉词典》
• I never saw so many darts in a bodice! 我从没见过紧身胸衣上纳了这么多的缝褶！ 来自《简明英汉词典》

3 premium   

n.加付款；赠品；adj.高级的；售价高的

参考例句：

• You have to pay a premium for express delivery.寄快递你得付额外费用。
• Fresh water was at a premium after the reservoir was contaminated.在水库被污染之后，清水便因稀而贵了。

4 unifying   

使联合( unify的现在分词 )； 使相同； 使一致； 统一

参考例句：

• In addition, there were certain religious bonds of a unifying kind. 此外，他们还有某种具有一种统一性质的宗教上的结合。
• There is a unifying theme, and that is the theme of information flow within biological systems. 我们可以用一个总的命题，把生物学系统内的信息流来作为这一研究主题。

5 uncertainty   

n.易变，靠不住，不确知，不确定的事物

参考例句：

• Her comments will add to the uncertainty of the situation.她的批评将会使局势更加不稳定。
• After six weeks of uncertainty,the strain was beginning to take its toll.6个星期的忐忑不安后，压力开始产生影响了。