讲解一下GMAT逻辑题里的思维陷阱

　　相信同学们在做GMAT逻辑题的时候养成了排除无关选项的习惯。不错，因为在选项设置上，5个选项中有很大概率一半以上的选项是无关的，所以先把这些明显“答非所问”的选项排除，然后在相关度较高的剩余选项中筛选、验证，是我们一般的解题思路。其中有很多的陷阱，今天小编就来给大家讲解一下逻辑题里的思维陷阱。
　　快速排除错误选项的能力，尤其是判断无关选项的能力，在考试中显得尤为重要，所以我们在课上总结了一系列无关选项的特征，比如：some代表无意义概率，other(than)代表扩大逻辑范围，比较级…than…一般是无关比较，高级以及太的词一般优先排除等等。
　　话虽如此，但事无。课上讲的无关选项的特征只是一般情况，不代表不会偶尔耍一下“小聪明”，出一些“看似错误”的选项迷惑我们。仔细想想，找到出题者的“套路”固然是件好事，但是太过依赖它导致无法发挥自己的“批判性思维”，将思维固化，就犯了GMAT考场上的兵家大忌—因为CR本身考得不是别的，就是我们对逻辑的批判。如果指望记住一些套路就能以不变应万变，单单记住一些正确选项以及错误选项的特征就觊觎高分，那只能说同学们还是太天真了。
　　下面，让我们一起分析几道“正确选项乍一看不像正确选项”的题，看看如何利用我们的思维陷阱。
　　例题1：A major network news organization experienced a drop in viewership in the week following the airing of a controversial report on the economy.The network also received a very large number of complaints regarding the report.The network,however,maintains that negative reactions to the report had nothing to do with its loss of viewers. Which of the following,if true,most strongly supports the network's position? (A)The other major network news organizations reported similar reductions in viewership during the same week. (B)The viewers who registered complaints with the network were regular viewers of the news organization's programs. (C)Major network news organizations publicly attribute drops in viewership to their own reports only when they receive complaints about those reports. (D)This was not the first time that this network news organization has aired a controversial report on the economy that has inspired viewers to complain to the network. (E)Most network news viewers rely on network news broadcasts as their primary source of information regarding the economy.正确答案是A。
　　题目大意是：一个主流的网络新闻组织在刊登了一篇富有争议的财经报道，在接下来的一周，该新闻组织经历了收视率的大幅下滑。同时该组织也收到了很多针对该报道的投诉。但是该组织拒绝把观众流失归咎于观众对财经报道的负面评价。
　　如果我们从选项的特征分析，很容易把A选项排除，因为A选项提到“other major network news organization”，而“other”通常意味着扩大讨论范围，所以带有other、other than的选项同学们一般会首先排除。但是，从相关性上来看，A选项又是合适的，因为只有A和“收视率下降”这个关键点有关。这里，根据“相关性优先”的原则，我们只能选择A选项。
　　来看看其他的错误选项。选项B，提出投诉的读者都是该新闻网站的长期读者，削弱了文中新闻网站组织的立场，反向逻辑，排除。选项C，主流网络新闻媒体只在接到投诉的状况下才会将读者数量下降归咎于他们自己的报道，也削弱了该新闻组织的立场，反向逻辑，排除。选项D，这不是该新闻网站一、次因为有争议的报道而收到投诉，无法加强该组织立场，无关。选项E，大多数网络新闻读者将网络新闻作为他们主要的财经类新闻消息来源，同样无法加强该组织的立场，无关。所以，用排除法也能证明A选项为正确答案。
　　这道题说明了一点，在判断选项正误上，相关性是非常重要的参考标准；与此同时，不能看到“other/other than”这样的词就草率地排除一个选项（还要看其相关性）。
　　例题2：In an experiment,each volunteer was allowed to choose between an easy task and a hard task and was told that another volunteer would do the other task.Each volunteer could also choose to have a computer assign the two tasks randomly.Most volunteers chose the easy task for themselves and under questioning later said they had acted fairly.But when the scenario was described to another group of volunteers,almost all said choosing the easy task would be unfair.This shows that most people apply weaker moral standards to themselves than to others. Which of the following is an assumption required by this argument? A.At least some volunteers who said they had acted fairly in choosing the easy task would have said that it was unfair for someone else to do so. B.The most moral choice for the volunteers would have been to have the computer assign the two tasks randomly. C.There were at least some volunteers who were assigned to do the hard task and felt that the assignment was unfair. D.On average,the volunteers to whom the scenario was described were more accurate in their moral judgments than the other volunteers were. E.At least some volunteers given the choice between assigning the tasks themselves and having the computer assign them felt that they had made the only fair choice available to them.正确答案是A（又是A？！）。
　　一般来说，我们看到“some”这个单词，会把选项当做“无意义概率”排除。但是，这道题里选项C和选项E都有“some”这个词，所以这道题不是单单考察“无意义概率”选项的排除，此题另有玄机。
　　事实上，这是一道补充必要条件的assumption题，也是加强题的一种，我们除了考虑选项的相关性之外，还要注意的就是选项的验证，也就是将选项取否定形式，能否推翻结论。
　　下面，我们一起来分析这道题的逻辑链。
　　条件：
　　一组人：我们(themselves)选择easy是fair的
　　第二组人：他们(others)选择easy是unfair的
　　结论：
　　most people apply weaker moral standards to themselves than to others
　　gap是一、组人评价自己，第二组人评价别人，而评价道德标准是同一个人针对不同的行为做出评价，A就是消除gap：选择easy的人认为对themselves是fair的而对others这么做就是unfair的，所以A选项正确。
　　当然，从相关性上来说，A选项也是贴近题干结论的，B选项the most moral choice无关逻辑链，C选项再重复条件，D选项more accurate取非无法削弱结论，E选项the only fair choice available同样无关，用排除法也可以选出A选项。
　　这道题提醒我们不能看到“some”就当做“无意义概率”草率排除。
　　例题3：With seventeen casinos,Moneyland operates the most casinos in a certain state.Although intent on expanding,it was outmaneuvered by Apex Casinos in negotiations to acquire the Eldorado chain.To complete its acquisition of Eldorado,Apex must sell five casinos to comply with a state law forbidding any owner to operate more than one casino per county.Since Apex will still be left operating twenty casinos in the state,it will then have the most casinos in the state. Which of the following,if true,most seriously undermines the prediction? A.Apex,Eldorado,and Moneyland are the only organizations licensed to operate casinos in the state. B.The majority of Eldorado's casinos in the state will need extensive renovations if they are to continue to operate profitably. C.Some of the states’counties do not permit casinos. D.Moneyland already operates casinos in the majority of the states’counties. E.Apex will use funds it obtains from the sale of the five casinos to help fund its acquisition of the Eldorado chain.正确答案是A。（三道题都是A选项？？！！嗯，是不是有什么奇怪的规律？不会就选A？）
　　通常正确答案不会用太的词，比如：only，most，first，best，all，none，initially等等，所以按照一般做题规律，这道题的A选项首先要排除，因为有“the only organizations’这样的表达。为什么这道题正确答案可以是“only”这样的表达呢？因为这道题和数量有关。
　　题目大意：M在某一个州拥有17家赌场，比其他公司的赌场数量都多。其竞争对手A赌场收购了E连锁赌场，从而打败了企图扩张的M。但为了完成收购，A必须要卖掉5家赌场来遵守州法律，法律规定每家企业在同一个county多只能拥有1家赌场。
　　结论：卖掉这5家赌场，A在该州依旧拥有20家赌场，从而将成为该州拥有多赌场的公司。

　　这道题是一个削弱题，我们需要找能说明“A选项在卖掉5家赌场后不是拥有多赌场的公司”的选项。本题的论述实质是横向和纵向的比较，结论是横比，比较这个州所有的赌场，谁家赌场数量多，横比只有在时间、地点相同的前提下才成立。但论据只讲了A的纵向变化，卖掉了5间赌场，收购了E的赌场后，现在拥有20间赌场，比之前M的17家赌场多。但拿A的现在和M的过去比较，是不符合逻辑的。单独只讨论A的变化，而不讨论与此同时本州其他赌场数量的变化是无法证明同一时间下20就是否是大数字的。因此只要能说明现在还有其他赌场经历了一些变化，拥有的赌场数量可能超过20就可以削弱结论了。
　　A选项说，该州只有A,E,M这三家合法赌场，也就是说A为了收购E而卖掉的5间赌场只能卖给M，那么M现在的赌场数量就变成了17 5=22>20，削弱了结论。B选项，E在该州的大部分赌场需要大范围的翻修才能在实际运营中带来利益。结论没有讨论到利益的问题，单纯只是比较谁家赌场数量多，无关。C选项，该州的一些county不允许开赌场。这只能说明这些county谁家都没有赌场，不能说明谁家赌场多。D选项，M在该州的大部分county都已经有赌场了。这只能说明M要扩张，只能是开发更多的county，无法说明能否开发成功，如果成功的话后M的总数能否超过20，都是未知数，无法影响结论（注意，有同学会因为错误理解原文意思而选错这个选项，原文说的是法律禁止同一家企业在一个county拥有2间甚至更多赌场，而不是说同一个county一共只能有多1间赌场，所以M和A在同一个county不存在不是你死就是我活的竞争关系）E选项，A会用卖5间赌场得到的钱作为收购资金。这和收购完成之后谁拥有多赌场无关。
　　综上所述，A选项为正确答案。
　　这道题给我们的启示是，当题目和数量、时间等数字相关时，选项中出现only、all、none等的表达不一定错误，有可能给出限定条件达到题目的要求。