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#15 - Amoebas, like human beings, generally withdraw from

PowerScore Staff
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Complete Question Explanation

Parallel Flaw—CE. The correct answer choice is (A)

The argument in this stimulus proceeds by analogy, reaching an overly broad and improperly definitive causal conclusion.

The stimulus author begins by describing how amoebas generally withdraw from things that cause them physical damage. Humans do the same, and it is pain that causes humans to withdraw. Based on this fact, and by means of an analogy, the author concludes that “all microscopic organisms must also be capable of feeling pain.”

This argument has two primary features. First, it proceeds by analogy. The author shows that amoebas, which are microscopic organisms, and human beings, are similar in one way—they both withdraw from stimuli that harm them physically. Based on this similarity, the author infers that microscopic organisms and human beings must be similar in another way—the same thing, pain, causes both to withdraw.

This analogy is flawed in two ways. First, the original comparison was between amoebas and humans, yet the conclusion refers to all microscopic organisms. While it may be the case that this extrapolation from amoebas to all microscopic organisms is accurate, the leap is logically invalid. To reach this conclusion, the stimulus would need to provide additional information establishing that all microscopic organisms share this characteristic with amoebas.

The conclusion is definitive in two areas—all microscopic organisms must also be capable of feeling pain. We have discussed the flaw in the shift from amoebas to all microscopic organisms. The second definitive portion, that they must be capable of feeling pain, is the result of the causal reasoning flaw.

While humans withdraw due to pain, that fact does not establish that microscopic organisms withdraw for the same reason. In fact, the stimulus explicitly provides a potential alternate cause for the organisms’ withdrawal—physical damage. Because the evidence does not provide a basis for dismissing this, or any other, alternate cause for the organisms’ withdrawal, the author’s implicit inference that amoebas withdraw as a result of pain is flawed. And, it is this flaw that leads to the author’s conclusion that all microscopic organisms must be capable of feeling pain.

The question stem identifies this as a Parallel Reasoning—Flaw question. The correct answer choice will contain an argument with similarly flawed logic, meaning the conclusion results from two flaws: the shift from a subset to the whole group, as in the shift from amoebas to all microscopic organisms; and the causal reasoning flaw.

Answer choice (A): This is the correct answer choice, because it displays both logical reasoning flaws. While the first premise establishes the analogy using poets and people under hypnosis, the conclusion deals with all artists. This is similar to the shift from amoebas to all microscopic organisms in the stimulus. Also, the author definitively concludes that artists must have lower inhibitions than most people, implying that the odd, incomprehensible use of language by poets must be caused by their lower inhibitions.

Answer choice (B): We can quickly dismiss this answer choice by using the Match the Conclusion test, in which we compare the language of the conclusion in the stimulus to the language of the conclusion in this answer choice. In order to display the same causal reasoning flaw that appeared in the stimulus, the conclusion here must be definitive. However, the language is merely probabilistic, stating that the desire to make the world better is probably also the main motive of most corporations. Also, this argument does not include the flawed shift from a subset to the entire group. In fact, the conclusion dials back the breadth of the conclusion, going from corporations in the premise to most corporations in the conclusion.

Answer choice (C): As with answer choice (B), the conclusion to the argument in this choice is probabilistic. Also, the argument deals with two subsets, professional boxers and professional skaters, of the same group, professional athletes, further distinguishing this answer choice from the stimulus, which compared microscopic organisms to humans.

Answer choice (D): This answer choice is very similar to answer choice (C). It also has a probabilistic, rather than a definitive, conclusion. And, it compares predatory birds and predatory mammals, both of which fall under the broader category of predatory animals.

Answer choice (E): This is the most tempting answer choice, because it reflects the causal flaw. The premises tell us that the New Mexico hiking trails are concentrated in mountainous regions partly because the low-lying areas, which are quite hot and arid, make for uncomfortable hiking. The conclusion then reaches a definitive conclusion that the reason hiking trails in British Columbia are similarly concentrated in mountainous areas must be that the low-lying areas make for similarly uncomfortable hiking. However, the argument does not commit the flaw in which the conclusion is overly broad, as occurred with the shift from amoebas to all microscopic organisms in the stimulus.
LSAT Apprentice
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Hi Powerscore,

I got the answer right because I recognized that the author seemed to be making somewhat of a generalization, going from two cases to "all microscopic organisms" and matched the conclusion. I did not however recognize the causal reasoning error. After reading the explanation I understand it a lot better.

Can it also be said that the author made an assumption that amoebas withdraw from these stimuli because it causes physical damage (i.e. pain). Before reading the explanation, I think I also made somewhat of a similar assumption. Boy, this question sure would have been easier if it was an assumption one :lol:
Eric Ockert
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Hi there!

The author is definitely assuming that amoebas exhibit this reaction because of pain. However, pain and physical damage are not the same thing. Basically, the author's argument can be summed up as:

Both humans and amoebas have a similar reaction to physically damaging stimuli. Humans have the reaction because of pain. Therefore, amoebas must also have the reaction because of pain.

Hope that clarifies a bit!
Eric Ockert
PowerScore LSAT/GMAT/SAT Instructor