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As you get older, learning often feels harder than it used to. Why is that? What changes in the brain as we age that makes acquiring new information harder? Is there anything we can do to avoid our minds slowing down? 随着年龄增长，常常会觉得学习变得比过去更难了。为什么会这样？大脑随年龄发生了哪些变化，导致获取新信息变得困难了？我们能做些什么来避免思维的衰退吗？ This is a topic I’ve been asked about a lot, but until recently one that I didn’t know much about. Aging wasn’t a topic I spent much time researching in my book, preferring to focus on principles of learning that are universal. 这是我经常被问到的一个问题，但直到不久前，我对此都了解不多。衰老不是我在书中花大量时间研究的主题，我更关注通用的学习原则。 Recently, however, I decided to dig into some of the research on cognitive aging to see how our learning is impacted by getting older. 不过，最近我决定深入了解一些关于认知老化的研究，看看我们的学习能力是如何受年龄增长的影响的。 Learning Slows with Age 学习随年龄增长而变慢 The first clear finding is that the feeling that one is getting slower mentally as we age is not an illusion—countless studies reinforce the fact that most aspects of mental processing get worse as we age:1 第一个明确的发现是，人们觉得随着年龄增长，思维会变慢，这并不是幻觉——无数研究都强调了这一事实，即认知加工的大部分方面都会随衰老而减退。 Interestingly, not all aspects of thinking get worse with age. Accumulated knowledge of the world increases until nearly the end of our lives, as you can see in the figure above with vocabulary size. 有趣的是，并非思维的所有方面都会随年龄增长而变差。直到生命的最后，我们累积的关于世界的知识都在增长，如上图中词汇量大小所示。 This is a trade-off between what researchers call fluid intelligence and crystallized intelligence. Even if our minds slow down as we get older, we accumulate more experience. We know more as we age, even if we’re slower at learning and processing new information. Wisdom increases even as wit declines. 这是研究人员所称的流体智力与晶体智力之间的此消彼长。尽管我们的思维随着年龄增长变缓了，但我们也随时间积累了更多的经验。尽管我们学习和加工新信息的速度变慢了，但我们也随时间流逝知道得更多。智力减退，但智慧却增加了。 What Gets Worse With Age? 随年龄增长什么变差了？ There are different hypotheses about how our minds tend to get worse as we get older. A simple one is the idea that processing speed slows down as we age—neurons lose mylenation and so the signals that carry the currents of our thinking slow down.2 关于我们的思维随年龄增长如何退化，有不同的假设。一个简单的假设认为，随着我们变老，信息加工的速度变慢了。神经元的髓鞘形成减少，导致携带思维电波的信号传输速度减慢。 Other researchers disagree, arguing that aging impacts some brain areas more severely than others, resulting in specific deficits of cognition rather than an overall decline. 另一些研究人员持不同意见，认为衰老对某些大脑区域的影响比另一些更严重，结果是特定的认知能力减弱，而不是整体的退化。 The frontal aging hypothesis argues that the frontal cortex is hit harder by aging.3 The frontal cortex is involved in many functions, but a key one is in asserting top-down executive control over our actions. This is often associated with the deliberate effort it takes to override habits or consciously keep intentions in mind when completing tasks. 额叶衰老假设认为，额皮质受衰老影响更大。很多认知功能都涉及额皮质，但一个关键功能是对我们的行为进行自上而下的控制。这通常可见于有意识地克服习惯，或在完成任务时有意识地在心里想着任务的目的。 Researchers Todd Braver and Robert West argue for a goal maintenance account of cognitive aging.4 Following the frontal aging hypothesis, this suggests that what is harder to do as you get older is to maintain and switch the goals associated with a task. This results in older individuals struggling more with Stroop tasks, where an automatic habit needs to be overridden by instructions: 研究人员托德·布拉维尔（Todd Braver）和罗伯特·韦斯特（Robert West）主张从目标记忆的角度解释认知衰老。按照额叶衰老假设，这意味着随年龄增长，困难的是记住和切换与一项任务相关的目标。因此年长的人在完成斯特鲁普式任务时遇到更多困难，因为需要遵照指令克服下意识的习惯。 Additionally, older individuals are hurt more by multitasking than younger people.5 This seems to be because multitasking requires switching the goals of the task at hand over a short period of time. Since older people have a harder time maintaining these, switching tasks frequently is particularly hard. 除此以外，在多任务处理上，年老的人也比年轻的人表现更差。这或许是因为多任务处理需要在短时间里切换手上执行任务的目标。由于年长的人更难记住目标，频繁切换任务对他们尤其困难。 Another deficit observed in older individuals is difficulty with binding information that occurs in a combined context.6 Chunking is one of the most important parts of learning new information, so the fact that this becomes harder with age may explain why learning new things feels more difficult as we get older. 在老年人身上观察到的另一衰退，是难以将关联情境中的信息组合起来。组块是学习新知识时最重要的一环，因此它随年龄增长变得困难，也就解释了为什么随着我们老去，学习新东西会感到困难。 Difficulty binding information together to store in long-term memories also impacts our ability to remember our life events. Simple information is less impacted by aging, but as we get older we may start to forget the context in which something was learned.7 The person you walk by looks familiar, but you forget where you met him before. 难以将信息关联到一起，存储在长期记忆中，也影响了我们记住生活中发生事情的能力。简单的信息不太受衰老的影响，但随着我们年龄增加，可能会开始忘记得知某件事的具体情境。路过的那个人看着眼熟，却想不起来你之前是在哪里见到他的。 The story isn’t all gloomy. In addition to crystallized knowledge, older people seem to be better at emotional regulation as well.8 Since managing emotions is an important part of success at many tasks, this suggests older people may be slower but surer at working on goals that have a bit of frustration baked in. 事情也不全然那么糟糕。除了晶体智力外，老年人似乎也更擅长情绪管理。鉴于情绪管控是做成许多事情的重要方面，这表明年龄大的人在面对可能遇到挫折的目标时，或许进展缓慢，但步伐坚定。 Do Different People Experience Decline Differently? 不同人经历的认知衰退会有不同吗？ Do all people experience cognitive decline uniformly? Or do some people’s minds slip while others stay sharp much longer? 所有人经历的认知衰退都是一样的吗？还是有些人的思维衰退，另一些人却能长期保持敏锐？ There seems to be a little conflict on this point in the research. One literature review I found argues in favor of cognitive decline being mostly linear as we age and not increasing in variance.9 This suggests that, absent illness, we’re all on roughly the same trajectory of cognitive slowdown. 在这一点上，研究还没有达成共识。我找到的一篇文献综述认为，随着年龄增长，认知的衰退几乎是线性的，而且人与人之间的差异也没有增加。这意味着，如果没有疾病，我们都会经历大致一样的认知衰退轨迹。 The lefthand graphs show decline of cognitive function, while righthand graphs show the variability. At least according to this study, variability doesn’t show dramatic increases with age. 左边的图显示认知功能的衰退，右边的图显示不同人之间的差异。至少从这个研究来说，差异没有随年龄增长表现出明显的增加。 This review, in contrast, seems to differ.10 The authors argue that variance increases with age, which goes with our normal intuition that some people seem to experience large declines in thinking with time while others fair much better. This seems to match up with other evidence that most factors associated with aging experience increasing variability over time. 相反，这篇评述似乎得出不同的结论。作者认为，人与人之间的认知差异随年龄增长也在增加，这符合我们一般的直观感受，即有些人似乎随时间流逝思维大幅减退，而另一些人却好得多。这似乎也与其他证据相印证，即与年龄有关的大多方面，都随时间表现出更大的差异性。 Redundancy and Cognitive Decline 冗余和认知衰退 One reason for the observation that some people seem to age mostly with minds intact and others notice dramatic slowdowns may be that the brain has a lot of redundancy built in. On a physical level, brain volume may be declining, but that this may not create noticeable difficulties for some time. 我们看到有些人的头脑几乎不受年龄增长的影响，而另一些人却表现出明显的衰退，原因之一可能是大脑本身有许多冗余。在生理层面上，大脑容量或许在减小，但在一段时间内不会产生明显可见的认知困难。 Cognitive reserve is the concept used by researchers to note that many individuals who experience decline on physical measures may not have related mental decline owing to this robustness.11 研究人员用认知储备这个概念来解释，正是因为这些冗余，许多根据物理测量大脑已经出现衰退的人，却没有表现出相应的思维退化。 One way you can see this is in fMRI scans which show that older individuals’ frontal cortices are more active than younger people’s on comparable tasks.12 Since frontal cortex decline is common in aging, what might be happening is that the brain is compensating for reduced efficiency by increasing activation. 你可以通过fMRI扫描观察到这一现象。面对同等的任务，老年人的额皮质比年轻人的更活跃。由于额皮质通常随年龄增加而减少，因此可能发生的就是，大脑通过增加活跃度来弥补功效的降低。 Researchers note that education seems to have a protective effect on aging.13 This may be because accumulated knowledge from education contributes to cognitive reserve, so as our minds decline, those who learned more when they were younger are better able to cope. Of course, another explanation might also be that those with sharper minds were more likely to go to school, and that education has no causal effect. 研究人员发现，教育似乎对衰老有保护作用。这或许是因为教育累积的知识增加了认知储备，因此当思维退化时，那些年轻时学得更多的人就能更好地应对。当然，另一种解释也可能是那些头脑敏捷的人更有可能去上学，因此教育并不是原因。 How Can Older People Reduce the Impact of Cognitive Decline? 老年人要如何减小认知衰退的影响？ There is some evidence that some aspects of cognitive aging can be overcome with training.14 However, I wouldn’t hold my breath for a magic fix. Age impacts our minds just as it does our bodies. Just as there is no exercise regimen that will allow a septuagenarian to compete in the Olympics, I doubt there are universal remedies for our cognitive declines. 有证据表明，认知衰老的有些方面可以通过训练得到克服。然而，我可不会屏息期待什么神奇的办法。衰老就像影响我们的身体一样影响我们的思维。正如没有哪种锻炼之道能让耄耋老人参加奥运会，我也不认为对于认知衰退存在普遍可行的补救办法。 However, the situation doesn’t seem to be completely without hope either. There do seem to be some things you can do to help your mental functioning. 然而，事情似乎也并非全然没有希望。你确实可以做些事情帮助头脑运转。 The first is preventing cognitive decline. Exercise and eat well when you’re younger. Learning more when you’re younger may minimize cognitive decline. Even if learning doesn’t prevent declines in fluid intelligence, it still enhances crystallized intelligence, giving you greater knowledge in your older years.15 首先是预防认知衰退。在年轻时坚持锻炼、健康饮食。年轻时多学习可以尽可能减少认知衰退。即使学习无法阻止流体智力的衰退，它也能提高晶体智力，使你在年老时拥有更多知识。 The second is to strategically control your environment to minimize the specific difficulties associated with aging. In particular, you should: 第二个办法是战略性地控制所处的环境，从而减少与衰老有关的具体困难。具体来说，你应该： 1. Avoid multitasking or environments with likely distractors. Since goal maintenance seems to be a central problem of aging, it means the older you are the more you benefit from an environment that allows your mind to focus on the problem at hand. 1 避免多任务工作，或处于可能让你分心的环境中。由于记住目标似乎是衰老会遇到的一个核心问题，这意味着年龄越大，待在能够让你专注于手上任务的环境中就越有帮助。 2 更有策略性地为重要信息创建线索和提示。前摄记忆指的是，预先计划之后看到特定的提示要回想起某件事。它尤其受到衰老的影响。这就意味着，设计你所处的环境，使之能够提醒你目标和要做的任务，随着年龄增长变得更加重要。 3 更加明确地组织你想要学习的内容。把不同信息勾连起来，使它们作为一块内容一起被回忆起来，既可以自动发生，也可以有意地促成。由于勾连信息随年龄增长变得困难，就更应该仔细组织想要学习的信息。 A third idea relates to how you might allocate your learning throughout your entire lifetime. Since fluid intelligence and complex working memory peak in early adulthood, this suggests that time might be the best for learning skills where those are more important, such as mathematics. 第三个办法涉及你在一生中应该如何分配学习时间。由于流体智力和复杂的工作记忆都在成年早期达到巅峰，这就意味着那段时间是学习重要技能的最佳时期，例如数学。 In contrast, for subjects that require mostly accumulated knowledge and build off of past habits of thinking, age may be an asset rather than a liability. History and law, for instance, may benefit more from this accumulated wisdom and be more amenable to improvements later in life. 相反，有些科目需要更多知识积累，依托过去的习惯和思考，年龄对于学习它们就是财富而不是负担。例如，历史和法学就更得益于累积的智慧，在年纪大些时更容易取得进步。 The idea that our minds change as we age, and thus change the relative ease of learning certain subjects shouldn’t be viewed fatalistically. Obviously, learning history when you’re fifteen or calculus when you’re fifty are both great. But understanding how age selectively impacts cognition can also help us to minimize the downsides of decline. 我们的头脑随年龄增加发生改变，因此改变了学习特定科目的相对容易程度，但不应该把这看成注定的。显然，十五岁时学习历史，五十岁时学习微积分，都是很棒的。但理解年龄如何有选择性地影响认知能力，也有助于我们减少认知衰退的负面作用。 Footnotes
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