经济学人杂志前段时间新出的专题，终生学习，许多篇文章，不自量力的学习翻译一下~
Old dogs, new tricks
老狗，新把戏
IF YOU ARE over 20, look away now. Your cognitive performance is probably already on the wane. The speed with which people can process information declines at a steady rate from as early as their 20s.
如果你年纪已经过了 20 ，那么看看你自己。你的认知能力可能已经在衰退了。从 20 出头的开始，人们对于信息的处理能力就会以一个稳定的速率下降。
A common test of processing speed is the “digit symbol substitution test”, in which a range of symbols are paired with a set of numbers in a code. Participants are shown the code, given a row of symbols and then asked to write down the corresponding number in the box below within a set period. There is nothing cognitively challenging about the task; levels of education make no difference to performance. But age does. Speed consistently declines as people get older.
一个被广泛采纳的用以测试信息处理速度的试验叫做“数字符号替换试验”，在这个试验中，将一系列的数字和符号配对并记录在本子上。参加试验的人员先阅读本子上的内容，然后再发给他们一个写着符号的表格，测试者需要在限定的时间内填写出相应符号所对应的数字。就这个试验而言并不存在认知能力上的挑战；受教育水平也同样与测试结果无关。但年纪却有影响。随着年纪的增大，回答速度便开始持续下降。
Why this should be is still a matter of hypothesis, but a range of tentative explanations has been put forward. One points the finger at myelin, a white, fatty substance that coats axons, the tendrils that carry signals from one neuron to another. Steady reductions in myelin as people age may be slowing down these connections. Another possibility, says Timothy Salthouse, director of the Cognitive Ageing Laboratory at the University of Virginia, is depletion of a chemical called dopamine, receptor sites for which decline in number with advancing age.
产生这种结果的原因的研究还处在假设阶段，但已经有一些可能的解释。有观点认为在髓磷脂的触角上，即一种被轴突覆盖的白色脂肪物质，这些触角负责从一个神经元向另一个传输信号。随着人类年龄增长而带来的髓磷脂的减少可能减慢了信号的传输速度。弗吉尼亚大学认知与年龄实验室的主任 Timothy Salthouse 提出了另一个猜想，他认为是由于多巴胺的减少，这些多巴胺受体随着年纪的增长而减少导致了这一现象的产生。
Fortunately, there is some good news to go with the bad. Psychologists distinguish between “fluid intelligence”, which is the ability to solve new problems, and “crystallised intelligence”, which roughly equates to an individual’s stock of accumulated knowledge. These reserves of knowledge continue to increase with age: people’s performance on vocabulary and general-knowledge tests keeps improving into their 70s. And experience can often compensate for cognitive decline. In an old but instructive study of typists ranging in age from 19 to 72, older workers typed just as fast as younger ones, even though their tapping speed was slower. They achieved this by looking further ahead in the text, which allowed them to keep going more smoothly.
辛运的是，年纪增长带来坏消息的同时也有一些好消息。心理学家指出了“流体智力”（即解决新问题的能力）和“晶体智力”（大致相当于一个个体所累积的经验和知识）的区别。知识的积累会随着年龄的增长而增加：人类的词汇量和一般性测试会持续增长直至 70 岁以上。而经验的积累通常可以弥补认知能力的下降。在一项较早进行的但具有指导性意义的试验中，通过对年纪处于 19-72 之间的打字员进行测试，即使年长的员工在输入速度上较低，他们在打字速度上年轻员工没有差别。而之所以会有这样一致的结果是因为年长的员工在打字时会提前观察之后的内容，这就使得他们打字过程更加顺畅。
What does all this mean for a lifetime of continuous learning? It is encouraging so long as people are learning new tricks in familiar fields. “If learning can be assimilated into an existing knowledge base, advantage tilts to the old,” says Mr. Salthouse. But moving older workers into an entirely new area of knowledge is less likely to go well.
那么这些研究对于终生学习而言有什么意义呢？对于人们在相似领域持续学习而言这是鼓舞人心的。Mr. Salthouse 说道“如果新学习到的知识能够融入已经存在的知识库中，那么年纪的增长就是一个优势”。但是让老员工去重新投入一个全新的领域效果就不怎么明显了。
