You Must Remember This:Forgetting Has Its Benefits

There's an old saying that inside every 70-year-old is a 35-year-old wondering, 'What happened?'

What happened is that countless days, nights, meetings, commutes and other unremarkable events went by, well, unremarked. They didn't make a lasting impression on the brain or they were overwritten by so many similar experiences that they are hard to retrieve. In short, they've been forgotten.

That's not necessarily a bad thing. Neuroscientists say forgetting is crucial to the efficient functioning of the mind, to learning, adapting and recalling more significant things.

'We focus so much on memory that forgetting has been maligned,' says Gayatri Devi, a neuro-psychiatrist and memory expert in New York City. 'But if you didn't forget, you'd recall all kinds of extraneous information from your life that would drown you in a sea of inefficiency.'

That was what prompted Jill Price to contact the memory experts at the University of California at Irvine in 2000. As she wrote in a book published this summer, 'The Woman Who Can't Forget,' Ms. Price could recall in detail virtually every day since she was 14, but she was mentally exhausted and tormented by her memories. UC Irvine scientists are interviewing more than 200 people who say they have similar 'autobiographical' memories, but so far have found only three more.

Memories of singular, significant events -- say, last week's historic election -- are generally easy to recall; people typically store them in long-term memory with many associations attached.

Memories of mundane, recurring events compete to be recalled, and scientists say the brain appears to be programmed to forget those that aren't important. Neuroimaging studies show that it's the brain's prefrontal cortex, the area of complex thought and executive planning, that sorts and retrieves such 'like-kind' memories. Researchers at Stanford University's Memory Laboratory demonstrated last year that the more subjects forgot competing memories, the less work their cortexes had to do to recall a specific one. In short, forgetting frees up brain power for other tasks, says psychologist Anthony Wagner, the lab's director.

A real-world example, he says, is having to learn a new computer password every few months: As your brain suppresses the memory of the old password, it gets easier to summon the new one.

In fact, forgetting is a very active process, albeit subconscious, neuroscientists say. The mind is constantly evaluating, editing and sorting information, all at lightning speed. 'Your brain is only taking a small amount in, and it's already erasing vast amounts that won't be needed again,' Dr. Devi says.

Much that happens during the day doesn't make an impression at all because our attention is focused elsewhere. Take your daily commute, says Dr. Wagner: 'A heck of a lot of stuff is landing on our retinas as we're driving down the road. But if you were focusing on the presentation you have to give, you didn't perceive it and it didn't get stored.'

He notes that people face such a constant cognitive barrage that they frequently fail to attend to information that isn't essential at the time. 'I have two 4 1/2-year-olds and I'm already thinking, where did those first four years go?' Dr. Wagner says.

Are memories for events you didn't focus on stored in your brain nevertheless -- like unwatched bank-surveillance tapes? That's an area of much debate. Some experts believe hypnosis can trigger long-buried associations. But so-called recovered memories are also susceptible to distortion.

'Memory consists of billions of puzzle pieces, and many of them look the same,' Dr. Devi says. 'Each time you retrieve a memory, you're reconstructing a puzzle very quickly and breaking it down again. Some of the pieces get put back in different places.'

What if you want to remember more about each passing day? One simple method is to keep a journal. Writing down a few thoughts and events every day not only makes a tangible record, it also requires you to reflect. 'You're elaborating on why they were meaningful, and you're laying down an additional memory trace,' says neuroscientist James McGaugh at UC Irvine. Taking photographs and labeling them reinforce memories too.

But remember that forgetting can be very useful, says Dr. McGaugh: 'If you used to go out with Bob and now you're married to Bill, you want to be able to say, 'I love you, Bill.' That's why forgetting is important.'

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句俗话是这样说的，每一个活到70岁的人都会有35年时间在琢磨：“到底发生过什么？”

发生过的就是，数不清的日日夜夜、会议、上下班和其他不足挂齿的事情悄无声息地溜走了。这些事情没有给大脑留下持久的印象，或是被如此多类似的经历覆盖了，因此难以回放出来。简而言之，它们都被遗忘了。

这不见得是件坏事。神经学家说，遗忘对大脑高效运转，学习、适应和回忆更有意义的事情至关重要。

纽约神经-精神学家、记忆专家德维(Gayatri Devi)说，我们对记忆是如此重视，以至于遗忘一直受到人们的诅咒。但如果你不忘记，你就会回忆起生活中所有无关紧要的信息，从而将你淹没在效率低下的海洋中。



Dan Picasso



这也是促使吉尔·普莱斯(Jill Price) 2000年联络加州大学欧文分校(University of California at Irvine)记忆专家的原因。正如她在今年夏季出版的图书《不能遗忘的女人》(The Woman Who Can't Forget)中写道的，普莱斯能够回忆起14岁以来几乎每一天的细节，但她在精神上深受这些回忆的困扰和折磨。加州大学欧文分校的科学家调查了200多名自称具有类似“自传式”记忆的人，但迄今为止仅另外发现了3例。

不同凡响的重大事件──比如几周前的历史性大选──通常容易回忆起来；人们一般会将这些事件同许多相关事情保存在长期记忆中。

对普通重复性事件的记忆则需要努力唤起，科学家称大脑看来设计了忘记那些无关紧要事件的程序。神经影像研究显示，是负责进行复杂思考和执行策划的大脑前置皮层筛选并唤起了这样的“同类”记忆。斯坦福大学(Stanford University)记忆实验室的研究人员去年指出，一个人忘掉的模糊记忆越多，其大脑皮层回忆起具体一件事就越容易。该实验室主任、心理学家安东尼·瓦格纳(Anthony Wagner)对此概括道，遗忘会解放执行其它任务的脑力。

他说，一个现实生活中的例子是每隔几个月就要记忆新的电脑密码。如果你的大脑压制了对旧密码的记忆，就会更容易想起新密码。

事实上，神经学家说，遗忘是一个非常活跃的过程，尽管人们意识不到这点。人的大脑会不断对信息进行评价、编辑和分类，一切都以极快的速度。德维说，你的大脑只接收了一小部分，而抹去了大部分不再需要的信息。

一天当中发生的多数事情都不会留下任何印象，因为我们的注意力集中到其它地方上了。以每天上下班路上的情形为例，瓦格纳说，当我们一路开车走过时，会有一连串的许多事情停留在我们的视网膜上。但如果你脑子里还在想着自己要做的一个演示，你就不会察觉这些东西，也不会记住它们。

他指出，人们会面临这种经常性认知阻碍，以至于他们常常不能注意到当时并非绝对必要的信息。瓦格纳说，我有两个四岁半的孩子，我现在已经在想，前四年的那些记忆都到哪里去了呢？

那么，有关那些你并不关注的活动的记忆会不会在你的大脑里储存下来、就像无人值守的银行监控录像一样呢？在这个问题上人们有很大争议。一些专家相信，催眠能激发出被长期埋藏的关联记忆。但所谓的被唤起的记忆也容易出现失真。

德维说，记忆由数十亿个思想片断组成，其中有很多看上去都一样。每次你获取记忆的时候，你都要非常迅速地重新构筑一个思想片断，然后再打碎它。有些片断会在不同时候得到恢复。

如果你想对过去的每一天保持更多记忆该怎么做呢？一个简单的方法是做记录。每天记下一些想法和发生的事情，这不仅能留下实实在在的记录，还能激励你去思考。加州大学欧文分校的神经学家麦克高夫(James McGaugh)说，“你会思考它们为什么是有意义的，同时也留下了额外的记忆痕迹。”拍摄照片并加上备注也能强化记忆。

但麦克高夫说，要记住，忘却对人可能很有帮助。如果你过去常跟鲍勃约会，但现在你跟比尔结婚了，你希望自己能说：“我爱你，比尔。”所以，能够忘却是很重要的。