Practice (or review) tends to build and maintain memory for a task or for any learned material. Over a period of no practice what has been learned tends to be forgotten; and the adaptive consequences may not seem obvious. Yet, dramatic instances of sudden forgetting can be seen to be adaptive. In this sense, the ability to forget can be interpreted to have survived through a process of natural selection in animals. Indeed, when one's memory of an emotionally painful experience lead to serious anxiety, forgetting may produce relief. Nevertheless, an evolutionary interpretation might make it difficult to understand how the commonly gradual process of forgetting survived natural selection.
In thinking about the evolution of memory together with all its possible aspects, it is helpful to consider what would happen if memories failed to fade. Forgetting clearly aids orientation in time, since old memories weaken and the new tend to stand out, providing clues for inferring duration. Without forgetting, adaptive ability would suffer, for example, learned behaviour that might have been correct a decade ago may no longer be. Cases are recorded of people who (by ordinary standards) forgot so little that their everyday activities were full of confusion. This forgetting seems to serve that survival of the individual and the species.
Another line of thought assumes a memory storage system of limited capacity that provides adaptive flexibility specifically through forgetting. In this view, continual adjustments are made between learning or memory storage (input) and forgetting (output). Indeed, there is evidence that the rate at which individuals forget is directly related to how much they have learned. Such data offers gross support of contemporary models of memory that assume an input-output balance.
67. From the evolutionary point of view, ________.
[A] forgetting for lack of practice tends to be obviously inadaptive
[B] if a person gets very forgetful all of a sudden he must be very adaptive
[C] the gradual process of forgetting is an indication of an individual's adaptability
[D] sudden forgetting may bring about adaptive consequences
68. According to the passage, if a person never forgets, ________.
[A] he would survive best
[B] he would have a lot of trouble
[C] his ability to learn would be enhanced
[D] the evolution of memory would stop
69. From the last paragraph we know that ________.
[A] forgetfulness is a response to learning
[B] the memory storage system is an exactly balanced input-output system
[C] memory is a compensation for forgetting
[D] the capacity of a memory storage system is limited because forgetting occurs
70. In this article, the author tries to interpret the function of ________.
[A] remembering
[B] forgetting
[C] adapting
[D] experiencing
重点词汇：
subsequent ------------ （随后的）←sub+sequ+ent，sub-在下，sequ(=follow)词根“跟随”，-ent形容词后缀。Be sure not to tell a first falsehood, and you needn't fear being detected in any subsequent ones.千万别说第一个谎话，这样就不用害怕在随后的谎话中被人发现。
duration ------------ （持久；持续时间）即dur+ation，dur词根“持续”，-ation名词后缀。同根词：durable（持久的）←dur+able可……的；endurance（持久力；忍耐力）←en使……+dur+ance。It is not the strength but the duration of great sentiment that makes great men.造就伟人的不是力量，而是伟大情操的持久。
contemporary ------------ （当代的；同时代的；同时代的人）←con+tempor+ary，con-一起，tempor看作temper（性情），-ary后缀，“性情相同的（人）就是同时代的（人）”。Most contemporary books give the impression of having been manufactured in a day, out of books read the day before.大部分当代书籍给人的印象，是花一天工夫用前一天读过的书加工而成的。I don't go along with all this talk of a generation gap. We're all contemporaries. There's only a difference in memories, that's all.我对代沟这种说法完全不能苟同。我们都是同时代的人，只是记忆有所不同，仅此而已。
难句解析：
①That experiences influence subsequent behaviour is evidence of an obvious but nevertheless remarkable activity called remembering.
▲本句的主语是个从句That experiences influence subsequent behaviour，而后面是一个简单的系表结构is evidence，只不过evidence后面的修饰成分较多，里面的两个形容词obvious和remarkable之间还用了but nevertheless来表达一种转折关系。
△注意在阅读的时候先要抓住主干结构，特别是主语从句。在表语的部分要能够一眼认出其核心结构是evidence of activity。
②Constant practice has such as effect on memory as to lead to skilful performance on the piano, to recitation of a poem, and even to reading and understanding these words.
▲本句的主干很简单，就是Constant practice has... effect on memory，主要的结构是such as... as...，在后一个as的后面有一个不定式，而这个不定式有三个并列的宾语to skilful performance on the piano, to recitation of a poem, and even to reading and understanding these words，注意这里的三个to都是介词，和动词lead构成词组。
△注意先抓主干结构，另外要注意such as... as...是一种举例子的形式。
③Over a period of no practice what has been learned tends to be forgotten; and the adaptive consequences may not seem obvious.
▲本句可一分为二，在分号处分开，前面的分句中over a period of no practice是个时间状语，主语是个从句what has been learned，谓语是tends to be forgotten，后面的结构非常简单。
△理解本句以及下面几句的功夫不在文字上，而是要求同学们对于进化论的假设和其与记忆的关系有一个明确的认识。在这里我们要知道，作者认为遗忘是一种生物在进化中适应外界残酷现实的适应性行为，因为只有忘掉了过去的不愉快经历，一个生命才有可能活得更加生机勃勃。而这样的观点的一种必然推论就是迅速遗忘要优于慢速遗忘，因为忘得越快就越能适应外部世界。那么在这里作者就指出用进化论适应性的观点来解释遗忘有局限性。
④Nevertheless, an evolutionary interpretation might make it difficult to understand how the commonly gradual process of forgetting survived natural selection.
▲本句的主语是an evolutionary interpretation，谓语might make，而宾语的部分比较复杂，有一个形式宾语it，在真正的作宾语的不定式中还有一个从句how the commonly gradual process of forgetting survived natural selection。
△注意理清句子结构，意思的理解请参看上句△部分。
⑤In thinking about the evolution of memory together with all its possible aspects, it is helpful to consider what would happen if memories failed to fade.
▲本句的主干是it is helpful to do sth.，真正的主语是to consider这个不定式，当然它里面还包含了一个带条件从句的宾语从句。逗号前面的是一个状语。
△注意在阅读的时候先要抓住主干结构，同时看清主句中的it是一个形式主语，指代的是后面的不定式结构。而前面的一个its应该是指memory。
⑥Another line of thought assumes a memory storage system of limited capacity that provides adaptive flexibility specifically through forgetting.
▲本句的主干是Another line of thought assumes a memory storage system，在这里assume是一个及物动词。宾语a memory storage system后面有一个of引导的介词词组和定语从句来修饰它。
△注意一些词的意思，capacity在这里应被理解为“容量”，而非“能力”；flexibility是“灵活性”而非“弹性”。
试题解析：
67. [D]
意为：突然失去记忆力会导致生存适应问题。
文章第一段指出，人生许多问题的解决依赖于我们对过去经历过的事情的记忆。第二段第二、三句指出，如果我们不及时复习或练习已学过的东西的话，过一段时间，我们可能忘记它，这种情况所造成的适应性(adaptive)后果也许不太明显。然而，突然失去记忆力却会对适应带来明显后果。举个例子来说，假如你一觉醒来，发觉自己失去了一切记亿，那样会发生什么呢？
A意为：由于缺乏练习所造成的遗忘很明显不利于生存适应。这与第二段第二句的意思相反。
B意为：如果一个人突然(all of a sudden)变得健忘，他肯定是非常适应生活的。这与第二段第三句表达的内容相反。
C意为：逐渐的遗忘过程证明了人的（较强的）适应能力。第二段第四句指出，遗忘可以被看作动物中自然选择(natural selection)过程中遗留给人的一种能力。第三段最后一句指出，遗忘（指逐渐的遗忘）似乎对每个个体或整个物种来说有其生存价值。可见，逐渐的遗忘过程是人在物种间的生存竞争过程中形成的，它是人们适应外部世界的结果。C则将人的适应能力看作是逐渐遗忘过程的结果，这显然颠倒了逻辑关系。
68. [B]
第三段第三、四句指出，没有遗忘过程，人就无法适应。例如，十年前正确的做法现在未必合适，所以应忘记它。对遗忘很少的人的调查也表明：他们的日常活动缺乏头绪。
A意为：他适于生存。这与事实相反。
C意为：他学习的能力会得到加强。这也与事实相反，事实是：所学的东西在大脑中会无头绪可寻。
D意为：记忆力的进化就会停止。
69. [A]
意为：遗忘是对学习的一种反应。
文章最后一段指出，对记忆力也可以做另一种解释：记忆的储存系统总储量有限，遗忘使这一系统具有了灵活性。这种看法认为：在学习或存储（输入）与遗忘（输出）之间有一个不断调整过程。事实上，有证据表明：遗忘率与学习的东西的量直接相关，这对现代记忆模式——输入——输出保持平衡——提供了证据。
B意为：记忆储存系统是一个输入输出完全平衡的系统。根据原文，确有一种理论认为或推测(assume)记忆储存系统是一个输入输出平衡的系统，但也仅是假设而已，另外，exactly一字用得欠妥，太绝对化。
C意为：记忆力是对遗忘的一个补偿。严格地来讲，forgetting与remembering都是memory的一个组成部分，是一个部分与整体间的关系，不能对照而言。
D意为：记忆的储存系统总储量有限，这是由遗忘造成的。原文只是说遗忘使记忆储存系统更具适应力，不是说它造成了记亿储存系统的有限性。
70. [B]
本文主要谈的是遗忘过程的作用(function)，它是人生存适应机制的一个很重要的过程，这是文章的第二、三、四段所旨在说明的，对照而言，第一段所谈的内容(remembering)只不过是这个讨论的引子。
A意为：记忆，记住。
C意为：适应。
D意为：体验。
全文翻译：
过去的经历会影响日后的行为，这就表明存在着一种明显但却非凡的脑力活动——记忆。如果没有大家称之为记忆的功能，学习便不能发生。反复练习对记忆有很大影响，可以使人们熟练地演奏钢琴、背诵诗歌、乃至总结和理解这些词句。用于解决问题或是辨别出有问题存在的所谓的智力行为需要记忆，记忆能力是推理的一个基本需求。解决任何问题，甚至是识别问题存在的能力都取决于记忆。最典型的是，决定过街也要凭借许多对以前经历的记忆。
实践（或称复习）就是建立并保持对某一任务或所学材料的记忆。有一段时间不实践，学到的东西往往就会忘记（渐进性地遗忘）；其适应性结果也就显得不太明显。然而戏剧性地突然遗忘的例子也可被看做具有适应性。从这个意义上说，遗忘能力可解释为动物在自然选择的过程中幸存下来的能力。的确，如果记住一段痛苦的情感经历会导致严重的焦虑，那么遗忘倒可以使人得到解脱。然而，进化论的解释可能会使人难以理解普遍的渐进遗忘过程是如何在自然选择中幸存下来的。
在考虑记忆的进化及其所有可能的方面时，思考一下如果记忆不会消失会产生什么结果是很有用处的。显然，遗忘有助于时间的定位，因为旧的记忆淡忘，新的记忆往往就突出，从而为推算持续的时间提供线索。没有遗忘，适应会受影响，例如，已学会的行为十年前可能是正确的，现在则不然了。有记录表明，有些人（按一般标准）忘的太少，以致日常生活常混乱不堪。因此遗忘似乎有助于个体及物种的存活。
另一种思路则假定人的记忆存储系统储量有限，这个系统专门通过遗忘提供适应的灵活性。根据这个观点，在学习或记忆储存（输入）和遗忘（输出）之间要不断进行调整。的确，表明个人的遗忘速度与学习东西的多少有直接的关系。这些数据为假定输入——输出持衡的当代记忆模式提供了明确的证据。
1994 Passage 1
The American economic system is organized around a basically private-enterprise, market-oriented economy in which consumers largely determine what shall be produced by spending their money in the marketplace for those goods and services that they want most. Private businessmen, striving to make profits, produce these goods and services in competition with other businessmen; and the profit motive, operating under competitive pressures, largely determines how these goods and services are produced. Thus, in the American economic system it is the demand of individual consumers, coupled with the desire of businessmen to maximize profits and the desire of individuals to maximize their incomes, that together determine what shall be produced and how resources are used to produce it.
An important factor in a market-oriented economy is the mechanism by which consumer demands can be expressed and responded to by producers. In the American economy, this mechanism is provided by a price system, a process in which prices rise and fall in response to relative demands of consumers and supplies offered by seller-producers. If the products is in short supply relative to the demand, the price will be bid up and some consumers will be eliminated from the market. If, on the other hand, producing more of a commodity results in reducing its cost, this will tend to increase the supply offered by seller-producers, which in turn will lower the price and permit more consumers to buy the product. Thus, price is the regulating mechanism in the American economic system.
The important factor in a private-enterprise economy is that individuals are allowed to own productive resources (private property), and they are permitted to hire labor, gain control over natural resources, and produce goods and services for sale at a profit. In the American economy, the concept of private property embraces not only the ownership of productive resources but also certain rights, including the right to determine the price of a product or to make a free contract with another private individual.
51. In line 8, paragraph 1, "the desire of individuals to maximize their incomes" means ________.
[A] Americans are never satisfied with their incomes
[B] Americans tend to overstate their incomes
[C] Americans want to have their incomes increased
[D] Americans want to increase the purchasing power of their incomes
52. The first two sentences in the second paragraph tell us that ________.
[A] producers can satisfy the consumers by mechanized production
[B] consumers can express their demands through producers
[C] producers decide the prices of products
[D] supply and demand regulate prices
53. According to the passage, a private-enterprise economy is characterized by ________.
[A] private property and rights concerned
[B] manpower and natural resources control
[C] ownership of productive resources
[D] free contracts and prices
54. The passage is mainly about ________.
[A] how American goods are produced
[B] how American consumers buy their goods
[C] how American economic system works
[D] how American businessmen make their profits
重点词汇：
market-oriented（以市场为导向的）←market市场+orient定位+ed形容词后缀。
permit ------------ （v.许可；许可证）即per+mit，per-(=through)，mit词根“传送”，故“允许传送过去”→许可。同根词：admit（v.让……进入；承认）←ad(=to)+mit；emit（v.散发，发射）←e(=ex)+mit；transmit（v.传播；传导）←trans(=through)+mit。Liberty is the right to do whatever the laws permit.自由就是做法律允许的任何事的权利。
embrace （v.拥抱；包含）即em+brace，em-(=in)，brace词根“手臂”，故“使在手臂里”→拥抱→引申为“包含”。brace作单词意为“v.支撑n.支柱”←谐音“不累死”，因为累死就支撑不住了。Created by life, in definite circumstances, to act on definite things, how can it embrace life, of which it is merely an emanation or aspect?由生命创造，处于一定情况下，作用于一定事物，它（←指科学）只是生命的一种释放或一个方面，怎么能包括生命？
coupled with 与……相结合；bid up 哄抬物价；gain control over 获得对……的控制。
难句解析：
①The American economic system is organized around a basically private-enterprise, market-oriented economy in which consumers largely determine what shall be produced by spending their money in the marketplace for those goods and services that they want most.
▲这是一个有定语从句和宾语从句的复杂句。首先要抓住的核心句为The American economic system is organized around a... economy，economy前面的定语在开始阅读时可以不看。在economy后面是一个以in which引导的定语从句in which consumers largely determine，而这个从句中又有一个宾语从句what shall be produced。在定语从句中又有一个by引导的分词结构spending their money in the marketplace for those goods and services that they want most作状语，说明消费者是如何决定应生产何种产品，而这个方式状语中又有一个定语从句that they want most。
△通过分析结构我们知道此句的所有意思都是围绕核心句的表语economy展开的，因此在阅读中应分层次，逐层理解对这一核心词的陈述，分清主次，全面理解。
②Thus, in the American economic system it is the demand of individual consumers, coupled with the desire of businessmen to maximize profits and the desire of individuals to maximize their incomes, that together determine what shall be produced and how resources are used to produce it.
▲首先要抓住句首的thus，看到这个词，就应想到此句是前面叙述引出的结论。再看句子结构，跳过状语in the American economic system，先抓住这是一个强调结构It is... that，因此所强调的部分是理解的重点，而它由三个平行成分组成，分别为the demand of individual consumers，the desire of businessmen to maximize profits和the desire of individuals to maximize their incomes，中间用coupled with和and连接。而在that后面的部分有两个并列宾语从句what shall be produced和how resources are used to produce it接在动词determine的后面。
△首先要抓住强调句型，并重点理解所强调的内容，其次要理解句中最后一个it所指代的对象是what shall be produced。
③An important factor in a market-oriented economy is the mechanism by which consumer demands can be expressed and responded to by producers.
▲此句的结构与第一句类似，只是表语的定语从句更加复杂。
△此句在理解中的难点是定语从句by which consumer demands can be expressed and responded to by producers，为了方便理解，我们可以将此句and后的部分由被动句改为主动句：by which consumer demands can be expressed and producers can respond to consumer demands，这样就可以避免对responded to by producers的不理解。
④If, on the other hand, producing more of a commodity results in reducing its cost, this will tend to increase the supply offered by seller-producers, which in turn will lower the price and permit more consumers to buy the product.
▲这是一个有条件状语从句的主从句，从句由if引导，主体结构为... producing more of a commodity results in reducing its cost...，其中producing more of a commodity是一个分词短语作主语，而主句以this为主语，里面包含一个定语从句which in turn will lower the price and permit more consumers to buy the product。
△此句在理解中的难点是句中代词的指代关系，其中第一个its所指的是commodity，而主句的主语this所指的是整个条件状语从句。主句中的定语从句也并不是修饰某一个特定的词，而是指整个主句表达to increase the supply offered by seller-producers。
⑤In the American economy, the concept of private property embraces not only the ownership of productive resources but also certain rights, including the right to determine the price of a product or to make a free contract with another private individual.
▲此句的主句结构为the concept embraces not only... but also...。主要的难点在其宾语部分，是一个not only... but also...连接的并列结构，而后面有一个长的补足语including the right to determine the price of a product or to make a free contract with another private individual。
