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二、假设题错误选项的形式 |
假设题属于推理链题，又称“演绎题”。所有推理链考题都会涉及的错误选项和诱惑选项类型：样本不足、诉诸大众、主观内容、循环论证（重复现象）。
这四个错误是所有推理链题中常见的，不仅限于假设题。
1. 样本不足
选项中提示样本不足的词汇有：some、few、certain、sample、small percentage等，也会有其他表示“小范围”“小样本”的内容。之前讲过“some”本身只是告诉我们数字大于零，至于会不会达到有代表性的程度我们并不清楚，完全可理解为含有some的事件只是一个特例。样本不足则没有代表性（not representative）。但是样本不足不意味着选项必错，只是属于高概率错误的选项。如果其他四个选项描述的事情和原文都无逻辑交集，只有一个选项与原文话题部分沾边，即使这个选项有“some”或类似词汇，我们也只能选择这个选项。
例1 Which of the following most logically completes the argument?
The irradiation of food kills bacteria and thus retards spoilage. However, it also lowers the nutritional value of many foods. For example, irradiation destroys a significant percentage of whatever vitamin B1 a food may contain. Proponents of irradiation point out that irradiation is no worse in this respect than cooking. However, this fact is either beside the point, since much irradiated food is eaten raw, or else misleading, since
A. many of the proponents of irradiation are food distributors who gain from food's having a longer shelf life.
B. it is clear that killing bacteria that may be present on food is not the only effect that irradiation has.
C. cooking is usually the final step in preparing food for consumption, whereas irradiation serves to ensure a longer shelf life for perishable foods.
D. certain kinds of cooking are, in fact, even more destructive of vitamin B 1 than carefully controlled irradiation is.
E. for food that is both irradiated and cooked, the reduction of vitamin B 1 associated with either process individually is compounded.
解析： 填空题其实就是演绎题的间接考法，实质是考查支持题、假设题、削弱题等。原文讲“辐照和营养减少”之间的关系，带着这个话题看选项。
A项描述“支持者和食物保质期”的话题，并不是在讨论“辐照与营养价值”。排除此项。
B项讲“杀菌不是辐照唯一的作用”，此项和“营养价值”无关，排除此项。
C项讲“辐照确保长的保质期”，和“营养价值”无关，排除此项。
D项发现比较级，要立刻思考比较关系和比较对象是否在原文中被提到过，有一项没有提到过即为无关对比。“certain cooking”既有诱惑词汇“certain”，又有无关对比内容。并且从逻辑意思角度分析，如果某种烹饪比辐照更有破坏性，那么能否说明辐照本身对营养的负面影响？我们并不能得知。所以排除此项。
E项包含了“辐照和营养降低（deduction of Vitamin B 1 ）”，是唯一的沾边选项，选E项。
切记： some指代的词汇没有代表性，但most、much指代的词汇有代表性。
例2 The chemical adenosine is released by brain cells when those cells are active. Adenosine then binds to more and more sites on cells in certain areas of the brain, as the total amount released gradually increases during wakefulness. During sleep, the number of sites to which adenosine is bound decreases. Some researchers have hypothesized that it is the cumulative binding of adenosine to a large number of sites that causes the onset of sleep.
Which of the following, if true, provides the most support for the researchers' hypothesis?
A. Even after long periods of sleep when adenosine is at its lowest concentration in the brain, the number of brain cells bound with adenosine remains very large.
B. Caffeine, which has the effect of making people remain wakeful, is known to interfere with the binding of adenosine to sites on brain cells.
C. Besides binding to sites in the brain, adenosine is known to be involved in biochemical reactions throughout the body.
D. Some areas of the brain that are relatively inactive nonetheless release some adenosine.
E. Stress resulting from a dangerous situation can preserve wakefulness even when brain levels of bound adenosine are high.
解析： 题目要求支持假说（hypothesis），则读文章时重点找假说的内容。如有选项谈到与假说相关的内容，则优选。
因为在实际考试中不可能记得很详细，所以考生可简单把原文读成“Adenosine结合多少”与“睡觉”之间的关系。
A项：“睡觉之后腺苷（adenosine）最低，结合的腺苷也非常多”，此项谈论了“睡觉与腺苷多少”相关的话题，属于沾边选项。
B项：“清醒与腺苷结合”的关系，清醒就是不睡觉，此项相当于也谈到了“睡觉和腺苷结合”的关系，此项待选。
C项：此项没有谈到“睡觉与腺苷”相关的话题，排除此项。
D项：出现了两个some，即使此项沾边也肯定不如A项、B项更好，因为这两项没有诱惑选项的词汇，成为答案的概率会高于D项。
E项：本项讲“清醒和腺苷”相关的话题，此项也沾边。
五个选项中A项、B项、E项三者都在谈论“清醒与腺苷”的关系，所以都为待选项。
比较选项前，可以先思考一下，如果你是出题人，你会如何让几个沾边选项中的一个成为答案？只有这几种可能性：情况一：假设有些不沾边，而是学生的误读，把一些不沾边的选项误认为是“有关选项”。情况二：假设所有待选项都沾边，则又分为两种情况——沾边选项的方向和题目问的一致、沾边选项的方向和题目所问的不一致。沾边选项和题目所问的都一致，则可以思考哪个选项出错概率小，或哪个选项和原文的距离最近。
在此题的A项、B项、E项对比中，可清楚地发现B项和E项是逻辑意思完全相反的关系，B项是“清醒与‘interfere with the binding’”，E项是“清醒和大量的‘bound’（bound意思等同于binding）”。此时，再核实一下原文的内容，原文的假说内容是“the cumulative binding of adenosine to a large number of sites that causes the onset of sleep”。“结合和睡觉”是正相关关系，试题问的是支持方向，所以B项优于E项。同时A项的意思是“睡觉之后腺苷的结合也会非常多”，和原文方向相反，排除A，即B项为正确答案。
2. 诉诸大众
解读： 此项逻辑错误是我们在日常生活中也会犯的类型，大众认为对的事情不一定是正确的。
例 Before the discovery of pellagra's link with niacin, it was widely believed that the disease was an infection that could be transmitted from person to person.
一直以来这个疾病被相信是人传人的感染，实际是如此吗？答案是无法判断。因为大众相信的东西不一定是事实，不可从这句话中得出这个病就是通过人际传染的。
3. 主观内容
解读： 逻辑论证具有客观性。人的思考具有主观性，只思考而不做出某些行为是不会对客观的世界有所影响的，从而也不会形成“逻辑演绎”。因此，如果选项只表达主观思考（知道、想要、激励、目标）等，而并没有采取行动，则基本可以排除此项。但如果原文问的就是一个人的主观想法，另当别论。
例 Newspaper editorial: In an attempt to reduce the crime rate, the governor is getting tough on criminals and making prison conditions harsher. Part of this effort has been to deny inmates the access they formerly had to college-level courses. However, this action is clearly counter to the governor's ultimate goal, since after being released form prison, inmates who had taken such courses committed far fewer crimes overall than other inmates.
Which of the following is an assumption on which the argument depends?
A. Not being able to take college-level courses while in prison is unlikely to deter anyone from a crime that he or she might otherwise have committed.
B. Former inmates are no more likely to commit crimes than are members of the general population.
C. The group of inmates who chose to take college-level courses were not already less likely than other inmates to commit crimes after being released.
D. Taking high school level courses in prison has less effect on an inmate's subsequent behavior than taking college-level courses does.
E. The governor's ultimate goal actually is to gain popularity by convincing people that something effective is being done about crime.
解析： （1）试题问“假设”，则要找一个和结论事件相同方向的选项。（2）原文读成：“减少犯罪率，让监狱变得更糟一些，不让罪犯接触到大学课程。但是这个有悖于政府最终目的，释放之后参加大学课程的人犯罪更少。”简单记为“参加课程与犯罪少”的关系。
A项可读成“不让罪犯参加课程不会阻止他们犯罪”，粗看起来此项与“参加课程与犯罪”沾边，但我们要找的方向是“参加课程与犯罪少”的关系，而此项是“不参加课程”与“犯罪少”的关系，所以A项排除。
B项并没有提到“课程与犯罪少”的话题，排除此项。并且此项犯了“无关对比”的错误。
C项肯定能读出“大学课程”与“犯罪少”的关系，保留此项。
D项谈到了“大学课程”但是没有讲“犯罪少”，排除此项。
E项，政府的目标与“大学课程和犯罪少”没有事实上的关联。
只有C沾边，正确答案为C。C项用了“排除他因”的方式进行增强。C项有一个“not”，意思是排除了参加大学课的人本身会更少犯罪的可能性，从而增加了是因为“大学课程”而不是“他们本身就会犯罪更少”导致的“犯罪少”。
4. 循环论证
解读： 在支持题中，如果选项重复了结论，可以是正确答案。但在假设题中，必须找一个原文没有说过的事件。此外，所有的逻辑题都不允许答案重复原文中“已经提到的事实”，或“已经告诉我们会成立的条件”。逻辑演绎过程就是生活中的场景。例如：A说“假如明天不下雨，你能陪我去看电影吗？”B如果回答“明天会下雨”算不算反驳了A？在生活中，算。GRE、GMAT考试中追求客观性逻辑，文章之外的情况我们都不能主观推理。生活充满了博弈，需要在和他人互动的过程中了解到其真实想法，要听出“话里有话”。但是这样的思想不可带进备考的状态，之前A说“如果明天下雨”，说明问的是在这个条件下，B会如何行动，而不是削弱条件本身。只驳斥条件，并没有回答A的提问。再比如，假设原文内容是“如果你中了1000万元彩票，你会给慈善机构捐款1000元”，问支持方向。选项A：你真的会中1000万元。选项B：你平时就有乐于助人的习惯。这两个选项哪个是支持？A项只是在重复条件，并没有说明有了这个条件之后你会采取什么样的行动。B项讲，你平时就乐于助人，所以会增加你做慈善的概率，因此答案是B项。
例 Smithtown University's fund-raisers succeeded in getting donations from 80 percent of the potential donors they contacted. This success rate, exceptionally high for university fund-raisers, does not indicate that they were doing a good job. On the contrary, since the people most likely to donate are those who have donated in the past, good fund-raisers constantly try less-likely prospects in an effort to expand the donor base. The high success rate shows insufficient canvassing effort.
Which of the following, if true, provides more support for the argument?
A. Smithtown University's fund-raisers were successful in their contacts with potential donors who had never given before about as frequently as were fund-raisers for other universities in their contacts with such people.
B. This year most of the donations that came to Smithtown University from people who had previously donated to it were made without the university's fund-raisers having made any contact with the donors.
解析： B项只是在重复原文中的事实——“since the people most likely to donate are those who have donated in the past”，因此B项不是答案。
A项的意思是Smithtown大学的募捐人和其他大学的募捐人在劝说那些不大可能捐款的人捐款的成功可能性上是一样的，说明别的大学未能劝说这些人捐款，Smithtown大学的人也未能成功。这样就不能说Smithtown大学的募捐人做得很好（doing a good job），属于支持的方向。此项的内容相当于在解释原文倒数第2句话“good fund-raisers constantly try less-likely prospects in an effort to expand the donor base”，好的募捐人应该让不太可能捐款的人群捐钱，而Smithtown大学的人并没有做得比别的学校的人更好，故A项正确。
假设题的错误选项类型如下：
（1）重复文章中描述的事情。
（2）与结论事件方向相反。
（3）选项支持结论，但与论证无关。
（4）逻辑顺序颠倒。
（5）其他无关选项。
类型1：重复文章中描述的事情
错误选项或重复前提，或重复结论，或重复原文已经描述的某个现象。
例 Radio stations with radio data system（RDS）technology broadcast special program information that only radios with an RDS feature can receive. Between 1994 and 1996, the number of RDS radio stations in Verdand increased from 250 to 600. However, since the number of RDS-equipped radios in Verdland was about the same in 1996 as in 1994, the number of Verdanders receiving the special program information probably did not increase significantly.
Which of the following is an assumption on which the argument depends?
A. Few if any of the RDS radio stations that began broadcasting in Verdland after 1994 broadcast to people with RDS-equipped radios living in areas not previously reached by RDS stations.
B. In 1996 Verdlanders who did not own radios equipped to receive RDS could not receive any programming from the RDS radio stations that began broadcasting in Verdand after 1994.
解析： 此题为假设题，表明选项和原文必须是“求同”的方向。
原文说了这些事：
（1）只有RDS收音机才能收听到特别电台节目。
（2）RDS发射站多了，但是RDS收音机数量一样。
（3）收到特别电台节目信号的人数并没有增加。
推理链就是前两件事情推出第三个件事情，来比较A项和B项。
A项可读成“很少有基站给这些人广播，他们在1994年之前是收不到信号的”。如果1994年之前收不到信号的人很多，而1994年之后因为基站多了，使这些人们能收到信号了，则原文的结论“收到信号的人数不多”就推不出来了。此项削弱后能使原文结论无法得出，属于必要条件的特征。此项可作为答案备选。
B项读成“没有RDS收音机就不能接收RDS的信号”。读到此时，学生会想如果一般的收音机也能收到RDS信号，那么接收信号的人数就增加了，同A项一样会导致结论得不出。但是，如果这样想的话，就犯了假设答案的错误。假设条件必须是原文未提及的条件，它能支撑原文结论成立，但在文章中没有说过类似事件。原文明确说了，只有RDS收音机才能接收到RDS信号，所以此项只是在针对“已有的事实”再说一次，B项不能成为答案。
A项为答案。
类型2：与结论所涉事件方向相反
假设条件是结合前提一起推出结论，必须和结论是一个方向性的内容。此条很容易理解。
类型3：选项支持结论，但与论证无关
假设相当于在前提与结论之间架一座桥，铺一条路，让前提能够顺利推导出结论。所以如果仅是增加结论成立的概率，而忽略了前提，不属于正确的假设条件。
例 A notched wooden stick from South Africa's Border Cave dating to 24,000 years ago contains the earliest evidence of humans using poison. Moreover, the poison applicator is just one of several artifacts, some dating to as early as 44,000 years ago, that resemble objects used by the San. Others include a digging stick, ostrich eggshell beads, carved pig tusks, bone arrowheads, and a lump of beeswax. Archaeologists have hypothesized that the finds indicate that San culture emerged about 44,000 years ago, making these the earliest link to a culture of modern humans.
Which of the following, if true, most strongly supports the archaeologists' hypothesis?
A. Carbon-dating of human skeleton indicates that human were not able to make artifacts until 44,000 years ago.
B. Successor cultures at given cave do not often adopt the style of agricultural implements used by earlier inhabitants of the same site.
分析： 此题为支持题，支持题和假设题一样，都承认结论正确，要找一个选项进一步增加结论成立的概率。题目问支持假说的选项，于是要从原文找到假说的内容。
文章说了以下这些事：
（1）一根木棒显示最早的用毒的证据。
（2）发现一些文物。
（3）从这些文物中推出了San文化出现的时间。
文章的结论是“San文化出现在4.4万年前”，前提是“一些物品追溯至4.4万年前”，所以推理过程是通过文物的时间推出San文化出现的时间。
A项读成“人类不能够在4.4万年前制作物品”，此项支持了结论，但此项和前提无关。我们要分析是否可以通过前提来得出结论，并不是通过其他角度单纯来支持结论，因为此项没有涉及“文物”相关内容，所以和推理链无关，不正确。
B项读成“之后的文化不会模仿之前的农具”。如果可以模仿，那么就不能从文物时间来推测出文化的时间，因此此项说到了“文物与文化”的关系，和原文的推理链沾边，得出答案为B项。
类型4：逻辑顺序颠倒
逻辑顺序颠倒类似“因果倒置”，这条不仅在假设题中常见，在支持题中也是高频考点。
例1 Researchers took a group of teenagers who had never smoked and for one year tracked whether they took up smoking and how their mental health changed. Those who began smoking within a month of the study's start were four times as likely to be depressed at the study's end than those who did not begin smoking. Since nicotine in cigarettes changes brain chemistry, perhaps thereby affecting mood, it is likely that smoking contributes to depression in teenagers.
Which of the following is an assumption on which the argument depends?
A. Participants who were depressed at the study's start were no more likely to be smokers at the study's end than those who were not depressed.
解析： 原文的推理链为“抽烟导致抑郁”。
A项：“抑郁的人不可能更容易成为抽烟者”。A项如果没有“no more likely to be”就会导致“因果倒置”，即不是先有抽烟再有的抑郁，而是先有抑郁再成为抽烟者。加上否定词就排除了因果倒置的可能。此项即为答案。
例2 In the Middle Ages, bloodletting was considered beneficial to health and the procedure was used to treat many illnesses, as well as to improve general health. Modern medicine has shown bloodletting to be harmful in treating many of the illnesses for which it was prescribed in the Middle Ages.Yet people who donate blood regularly to blood banks live longer, on average, than those who never donate blood, so bloodletting probably has some beneficial effect.
Which of the following, if true, points to an error of reasoning in the argument?
A. Medieval medical theories assigned a different role to the blood than modern medicine does.
B. Not all of the conditions for which medieval medicine prescribed bloodletting are worsened by the procedure.
C. Bloodletting diminishes a patient's ability to fight off certain kinds of infection.
D. Many people who donate blood regularly to blood banks do so less frequently in old age than they did when they were younger.
E. People who are not generally healthy are not permitted to donate blood to blood banks.
解析： 此题为削弱题，题目问在推理中有何错误。问法表明正确答案描述的事件一定是推理链内部说过的内容，不会通过其他事件来削弱推理链，因为问法是“推理过程中有哪个错误”，答案只能和推理过程相关联。
文章推理链是从“献血的人活得更久”推出“放血有好处”。
A项出现比较级，比较内容并没有在文章中出现，排除此项。
B项，not all 相当于some，放在名词前面，说明所指情况没有代表性，也是诱惑选项的信号词。此项不太好。
C项针对结论反着说，属于削弱的方向。前三个选项对比，C项胜出，可放着待选。
D项又发现一个比较级。两个比较对象（old age，younger）的对比在文章中并没有见到，所以此项和A项一样，犯了无关对比的错误，排除此项。
E项意思是“不健康的人不让献血”。原文中提到“献血会有好处（健康）”，此项和因果倒置相关。如果健康的人才允许被献血，就推理不出献血会有益健康这个说法了。E项正确。