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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? 隨著年齡增長(zhǎng)，常常會(huì)覺(jué)得學(xué)習(xí)變得比過(guò)去更難了。為什么會(huì)這樣？大腦隨年齡發(fā)生了哪些變化，導(dǎo)致獲取新信息變得困難了？我們能做些什么來(lái)避免思維的衰退嗎？ 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. 這是我經(jīng)常被問(wèn)到的一個(gè)問(wèn)題，但直到不久前，我對(duì)此都了解不多。衰老不是我在書(shū)中花大量時(shí)間研究的主題，我更關(guān)注通用的學(xué)習(xí)原則。 Recently, however, I decided to dig into some of the research on cognitive aging to see how our learning is impacted by getting older. 不過(guò)，最近我決定深入了解一些關(guān)于認(rèn)知老化的研究，看看我們的學(xué)習(xí)能力是如何受年齡增長(zhǎng)的影響的。 Learning Slows with Age 學(xué)習(xí)隨年齡增長(zhǎng)而變慢 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 第一個(gè)明確的發(fā)現(xiàn)是，人們覺(jué)得隨著年齡增長(zhǎng)，思維會(huì)變慢，這并不是幻覺(jué)——無(wú)數(shù)研究都強(qiáng)調(diào)了這一事實(shí)，即認(rèn)知加工的大部分方面都會(huì)隨衰老而減退。 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，并非思維的所有方面都會(huì)隨年齡增長(zhǎng)而變差。直到生命的最后，我們累積的關(guān)于世界的知識(shí)都在增長(zhǎng)，如上圖中詞匯量大小所示。 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. 這是研究人員所稱的流體智力與晶體智力之間的此消彼長(zhǎng)。盡管我們的思維隨著年齡增長(zhǎng)變緩了，但我們也隨時(shí)間積累了更多的經(jīng)驗(yàn)。盡管我們學(xué)習(xí)和加工新信息的速度變慢了，但我們也隨時(shí)間流逝知道得更多。智力減退，但智慧卻增加了。 What Gets Worse With Age? 隨年齡增長(zhǎng)什么變差了？ 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 關(guān)于我們的思維隨年齡增長(zhǎng)如何退化，有不同的假設(shè)。一個(gè)簡(jiǎn)單的假設(shè)認(rèn)為，隨著我們變老，信息加工的速度變慢了。神經(jīng)元的髓鞘形成減少，導(dǎo)致攜帶思維電波的信號(hào)傳輸速度減慢。 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. 另一些研究人員持不同意見(jiàn)，認(rèn)為衰老對(duì)某些大腦區(qū)域的影響比另一些更嚴(yán)重，結(jié)果是特定的認(rèn)知能力減弱，而不是整體的退化。 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. 額葉衰老假設(shè)認(rèn)為，額皮質(zhì)受衰老影響更大。很多認(rèn)知功能都涉及額皮質(zhì)，但一個(gè)關(guān)鍵功能是對(duì)我們的行為進(jìn)行自上而下的控制。這通?？梢?jiàn)于有意識(shí)地克服習(xí)慣，或在完成任務(wù)時(shí)有意識(shí)地在心里想著任務(wù)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: 研究人員托德·布拉維爾（Todd Braver）和羅伯特·韋斯特（Robert West）主張從目標(biāo)記憶的角度解釋認(rèn)知衰老。按照額葉衰老假設(shè)，這意味著隨年齡增長(zhǎng)，困難的是記住和切換與一項(xiàng)任務(wù)相關(guān)的目標(biāo)。因此年長(zhǎng)的人在完成斯特魯普式任務(wù)時(shí)遇到更多困難，因?yàn)樾枰裾罩噶羁朔乱庾R(shí)的習(xí)慣。 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，在多任務(wù)處理上，年老的人也比年輕的人表現(xiàn)更差。這或許是因?yàn)槎嗳蝿?wù)處理需要在短時(shí)間里切換手上執(zhí)行任務(wù)的目標(biāo)。由于年長(zhǎng)的人更難記住目標(biāo)，頻繁切換任務(wù)對(duì)他們尤其困難。 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. 在老年人身上觀察到的另一衰退，是難以將關(guān)聯(lián)情境中的信息組合起來(lái)。組塊是學(xué)習(xí)新知識(shí)時(shí)最重要的一環(huán)，因此它隨年齡增長(zhǎng)變得困難，也就解釋了為什么隨著我們老去，學(xué)習(xí)新東西會(huì)感到困難。 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. 難以將信息關(guān)聯(lián)到一起，存儲(chǔ)在長(zhǎng)期記憶中，也影響了我們記住生活中發(fā)生事情的能力。簡(jiǎn)單的信息不太受衰老的影響，但隨著我們年齡增加，可能會(huì)開(kāi)始忘記得知某件事的具體情境。路過(guò)的那個(gè)人看著眼熟，卻想不起來(lái)你之前是在哪里見(jiàn)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。除了晶體智力外，老年人似乎也更擅長(zhǎng)情緒管理。鑒于情緒管控是做成許多事情的重要方面，這表明年齡大的人在面對(duì)可能遇到挫折的目標(biāo)時(shí)，或許進(jìn)展緩慢，但步伐堅(jiān)定。 Do Different People Experience Decline Differently? 不同人經(jīng)歷的認(rèn)知衰退會(huì)有不同嗎？ Do all people experience cognitive decline uniformly? Or do some people’s minds slip while others stay sharp much longer? 所有人經(jīng)歷的認(rèn)知衰退都是一樣的嗎？還是有些人的思維衰退，另一些人卻能長(zhǎng)期保持敏銳？ 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. 在這一點(diǎn)上，研究還沒(méi)有達(dá)成共識(shí)。我找到的一篇文獻(xiàn)綜述認(rèn)為，隨著年齡增長(zhǎng)，認(rèn)知的衰退幾乎是線性的，而且人與人之間的差異也沒(méi)有增加。這意味著，如果沒(méi)有疾病，我們都會(huì)經(jīng)歷大致一樣的認(rèn)知衰退軌跡。 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. 左邊的圖顯示認(rèn)知功能的衰退，右邊的圖顯示不同人之間的差異。至少?gòu)倪@個(gè)研究來(lái)說(shuō)，差異沒(méi)有隨年齡增長(zhǎng)表現(xiàn)出明顯的增加。 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，這篇評(píng)述似乎得出不同的結(jié)論。作者認(rèn)為，人與人之間的認(rèn)知差異隨年齡增長(zhǎng)也在增加，這符合我們一般的直觀感受，即有些人似乎隨時(shí)間流逝思維大幅減退，而另一些人卻好得多。這似乎也與其他證據(jù)相印證，即與年齡有關(guān)的大多方面，都隨時(shí)間表現(xiàn)出更大的差異性。 Redundancy and Cognitive Decline 冗余和認(rèn)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. 我們看到有些人的頭腦幾乎不受年齡增長(zhǎng)的影響，而另一些人卻表現(xiàn)出明顯的衰退，原因之一可能是大腦本身有許多冗余。在生理層面上，大腦容量或許在減小，但在一段時(shí)間內(nèi)不會(huì)產(chǎn)生明顯可見(jiàn)的認(rèn)知困難。 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 研究人員用認(rèn)知儲(chǔ)備這個(gè)概念來(lái)解釋，正是因?yàn)檫@些冗余，許多根據(jù)物理測(cè)量大腦已經(jīng)出現(xiàn)衰退的人，卻沒(méi)有表現(xiàn)出相應(yīng)的思維退化。 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. 你可以通過(guò)fMRI掃描觀察到這一現(xiàn)象。面對(duì)同等的任務(wù)，老年人的額皮質(zhì)比年輕人的更活躍。由于額皮質(zhì)通常隨年齡增加而減少，因此可能發(fā)生的就是，大腦通過(guò)增加活躍度來(lái)彌補(bǔ)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. 研究人員發(fā)現(xiàn)，教育似乎對(duì)衰老有保護(hù)作用。這或許是因?yàn)榻逃鄯e的知識(shí)增加了認(rèn)知儲(chǔ)備，因此當(dāng)思維退化時(shí)，那些年輕時(shí)學(xué)得更多的人就能更好地應(yīng)對(duì)。當(dāng)然，另一種解釋也可能是那些頭腦敏捷的人更有可能去上學(xué)，因此教育并不是原因。 How Can Older People Reduce the Impact of Cognitive Decline? 老年人要如何減小認(rèn)知衰退的影響？ 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. 有證據(jù)表明，認(rèn)知衰老的有些方面可以通過(guò)訓(xùn)練得到克服。然而，我可不會(huì)屏息期待什么神奇的辦法。衰老就像影響我們的身體一樣影響我們的思維。正如沒(méi)有哪種鍛煉之道能讓耄耋老人參加奧運(yùn)會(huì)，我也不認(rèn)為對(duì)于認(rèn)知衰退存在普遍可行的補(bǔ)救辦法。 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沒(méi)有希望。你確實(shí)可以做些事情幫助頭腦運(yùn)轉(zhuǎn)。 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 首先是預(yù)防認(rèn)知衰退。在年輕時(shí)堅(jiān)持鍛煉、健康飲食。年輕時(shí)多學(xué)習(xí)可以盡可能減少認(rèn)知衰退。即使學(xué)習(xí)無(wú)法阻止流體智力的衰退，它也能提高晶體智力，使你在年老時(shí)擁有更多知識(shí)。 The second is to strategically control your environment to minimize the specific difficulties associated with aging. In particular, you should: 第二個(gè)辦法是戰(zhàn)略性地控制所處的環(huán)境，從而減少與衰老有關(guān)的具體困難。具體來(lái)說(shuō)，你應(yīng)該： 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 避免多任務(wù)工作，或處于可能讓你分心的環(huán)境中。由于記住目標(biāo)似乎是衰老會(huì)遇到的一個(gè)核心問(wèn)題，這意味著年齡越大，待在能夠讓你專注于手上任務(wù)的環(huán)境中就越有幫助。 2 更有策略性地為重要信息創(chuàng)建線索和提示。前攝記憶指的是，預(yù)先計(jì)劃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響。這就意味著，設(shè)計(jì)你所處的環(huán)境，使之能夠提醒你目標(biāo)和要做的任務(wù)，隨著年齡增長(zhǎng)變得更加重要。 3 更加明確地組織你想要學(xué)習(xí)的內(nèi)容。把不同信息勾連起來(lái)，使它們作為一塊內(nèi)容一起被回憶起來(lái)，既可以自動(dòng)發(fā)生，也可以有意地促成。由于勾連信息隨年齡增長(zhǎng)變得困難，就更應(yīng)該仔細(xì)組織想要學(xué)習(xí)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. 第三個(gè)辦法涉及你在一生中應(yīng)該如何分配學(xué)習(xí)時(shí)間。由于流體智力和復(fù)雜的工作記憶都在成年早期達(dá)到巔峰，這就意味著那段時(shí)間是學(xué)習(xí)重要技能的最佳時(shí)期，例如數(shù)學(xué)。 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識(shí)積累，依托過(guò)去的習(xí)慣和思考，年齡對(duì)于學(xué)習(xí)它們就是財(cái)富而不是負(fù)擔(dān)。例如，歷史和法學(xué)就更得益于累積的智慧，在年紀(jì)大些時(shí)更容易取得進(jìn)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. 我們的頭腦隨年齡增加發(fā)生改變，因此改變了學(xué)習(xí)特定科目的相對(duì)容易程度，但不應(yīng)該把這看成注定的。顯然，十五歲時(shí)學(xué)習(xí)歷史，五十歲時(shí)學(xué)習(xí)微積分，都是很棒的。但理解年齡如何有選擇性地影響認(rèn)知能力，也有助于我們減少認(rèn)知衰退的負(fù)面作用。 Footnotes
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