Animal feed should not include genetically modified plants. A study fo

Question

Animal feed should not include genetically modified plants. A study found that laboratory rats fed genetically modified potatoes for 30 days tended to develop intestinal deformities and a weakened immune system, whereas rats fed a normal diet of foods that were not genetically modified did not develop these problems.

Which one of the following, if true, most weakens the argument?

(A) Potatoes are not normally a part of the diet of laboratory rats.
(B) The rats tended to eat more of the genetically modified potatoes at the beginning of the 30 days than they did toward the end of the 30 days.
(C) Intestinal deformities at birth are not uncommon among rats bred in laboratory conditions.
(D) Genetically modified potatoes have the same nutritional value to rats as do potatoes that are not genetically modified.
(E) The researchers conducting the study were unable to explain how the genetic modifications of the potatoes would have caused the intestinal deformities or a weakened immune system in the rats.

Source: LSAT

ankitsaroha · Answer

Answer is C.

The argument assumes that the rats became sick only after eating the genetically modified potatoes. But, option C shows that maybe the rats were sick from the time they were born.

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prathi123 · Answer

Can someone please explain that why is A the answer here and not C?

siddharthharsh · Answer

Because even if it is common, it does not explain why there was difference between the two group.
In other words why didn't the group that was fed normal food did not develop Intestinal deformities.

(A) Potatoes are not normally a part of the diet of laboratory rats.
This clearly shows that one group was fed with potatoes and other with normal food. So it might be the case the difference observed may be because of potato, not necessarily because of genetic modification.

akela · Answer

Question Type:
Weaken

Stimulus Breakdown:
Premises:
1. Rats in a study that were fed GM potatoes for 30 days developed intestinal deformities and a weakened immune system.
2. Rats in the study that were fed a normal diet of non-GM foods did not have problems.

Conclusion:
Animal feed should not include genetically modified plants.

Answer Anticipation:
This argument leaves out a great deal of information that is needed to guarantee the conclusion. Maybe rats normally develop intestinal deformities and a weakened immune system if they eat potatoes. Maybe the rats were fed something else along with the potatoes that caused those problems, or maybe the first group of rats was more prone to the problems in the first place.

Even if the GM potatoes did cause the problems, can we conclude that animal feed should not include any type of GM plant? Can we conclude that any quantity of GM plant should be avoided, even a small quantity, for a short duration? The correct answer could highlight any of these gaps in the argument.

Correct Answer:
(A)

Answer Choice Analysis: 
(A) This is correct. If rats normally don't eat potatoes then it means we have a study where one group is eating a normal diet, and the other is eating an abnormal diet. It's very possible that this would cause the problems regardless of whether or not the potatoes were genetically modified.

(B) This comparison is irrelevant. Why do we care if the rats ate less potatoes toward the end of the study? This doesn't weaken. Intestinal deformities could cause the rats to eat less, no matter what was causing the deformities.

(C) Intestinal deformities at birth are irrelevant. The premises involve deformities that developed during the study.

(D) This is tempting, but doesn't weaken as much as (A). It eliminates one factor that might cause the GM potatoes to harm the rats. However, it still leaves open the possibility that the GM potatoes harmed the rats in some other way, so it's not a great weakener.

(E) Like (D), this might be tempting at first glance, but doesn't necessarily weaken. A study could demonstrate that something is harmful without the researchers being able to explain exactly how it causes harm. We don't know exactly how gravity works, but we know that jumping out of an airplane without a parachute is likely to be harmful.

Takeaway/Pattern: When the stimulus has multiple flaws it can be easy to anticipate a correct answer, but you may still have to decide between two or more tempting answer choices. The incorrect answers will leave too many possibilities open.

akela · Answer

PowerScore Complete Question Explanation

Weaken—CE. The correct answer choice is (A)

The author of this stimulus leads off with the conclusion, that “animal feed should not include genetically modified plants.” To support this conclusion, the author points to a study in which researchers fed one group of laboratory rats genetically modified potatoes for thirty days, while another set of rats were fed a “normal diet of foods that were not genetically modified.” The rats fed genetically modified potatoes tended to develop “intestinal deformities and a weakened immune system,” while the rats fed a normal diet did not.

As is often the case on the LSAT, there appear to be some issues with this study. Most glaringly, we do not know why potatoes were chosen as the genetically modified food, nor whether the rats were fed only potatoes, as opposed to a “normal diet of foods.” If the researchers both changed the rats’ normal diet and added genetically modified food, having both of those changes made simultaneously would cloud the issue of causation. Put another way, did the rats develop medical issues because they ate genetically modified food, or did those issues result from their thirty day diet of potatoes, regardless of the genetic modifications?

A separate issue is the generalization of the results from a study of rats to a conclusion about animal feed generally. Even if we assume that the rats’ medical issues resulted from their consumption of genetically modified potatoes, that evidence does not establish that other animals would be affected the same way the rats were affected.

The question stem indicates that this is a Weaken question. We can prephrase that the way the study was conducted, in which the researchers apparently both changed the rats’ diet and exposed the rats to genetically modified foods, makes the causation ambiguous, so that it may not be the case that genetically modified plants should be kept out of the rats’ feed, let alone animal feed.

Answer choice (A): This is the correct answer choice, because it introduces as fact our suspicion that the researchers not only introduced genetically modified food, but changed the rats’ normal diet as well. As discussed above, this information weakens the causal conclusion by raising the change from the rats’ normal diet, independent of the introduction of modified food, as an alternate cause for the negative change in the rats’ health.

Answer choice (B): Nothing in the stimulus suggests that when within the thirty day period the rats ate the majority of the modified potatoes has any impact on the causal relationship between the genetic modifications and the damage to the rats.

Answer choice (C): This answer choice has no connection to genetically modified food, and is irrelevant to the conclusion.

Answer choice (D): It is not clear what nutritional value potatoes have for rats. This answer choice may simply be saying that potatoes have zero nutritional value to rats with or without genetic modification. In any event, this comparison does not impact the implied causal relationship between genetic modification and the medical problems experienced by the rats.

Answer choice (E): This is a very tempting answer choice, because it explicitly mentions causality in a way that is negative for the researchers. Some taking the test thought that the inability of the researchers to explain how the genetic modifications would have caused the rats’ medical problems weakens the causal conclusion. However, the inability to explain a causal mechanism does not show there is not causality present.

https://forum.powerscore.com/lsat/viewtopic.php?t=13319

sumitmittal · Answer

Because it states about the Intestinal deformities but not about weakened immune system.

CEdward · Answer

Animal feed should not include genetically modified plants. A study found that laboratory rats fed genetically modified potatoes for 30 days tended to develop intestinal deformities and a weakened immune system, whereas rats fed a normal diet of foods that were not genetically modified did not develop these problems.

Which one of the following, if true, most weakens the argument?

(A) Potatoes are not normally a part of the diet of laboratory rats. 
 CORRECT . The study did not involve a fair comparison. On the one hand, some rats were fed genetically modified potatoes, whereas other rats were fed a 'normal diet'. So perhaps the reason for the illnesses were not the genetic modification of the plants, but the fact that the mice were being fed something unusual to begin with (potatoes).

(B) The rats tended to eat more of the genetically modified potatoes at the beginning of the 30 days than they did toward the end of the 30 days.

It's not particularly clear what this is meant to convey. Is the suggestion here that GMO potatoes caused these illnesses so that's why the rats ate less over time? If so, then that would seem to strengthen the argument.

(C) Intestinal deformities at birth are not uncommon among rats bred in laboratory conditions. X

The main contender, and I really had a hard time not choosing this one. But the reason it's wrong is because it does not eliminate the possibility that eating genetically modified foods can still cause those problems.

(D) Genetically modified potatoes have the same nutritional value to rats as do potatoes that are not genetically modified. X

"Nutritional value" is neither here nor there.

(E) The researchers conducting the study were unable to explain how the genetic modifications of the potatoes would have caused the intestinal deformities or a weakened immune system in the rats. X

This is irrelevant. Just because the researchers were unable to explain how the genetic modifications would have caused the problems does not mean those problems aren't tangible and real. Hence, E) doesn't give us any reason to think that the conclusion is invalid.

Foreheadson · Answer

Easy Question.

(A) Potatoes are not normally a part of the diet of laboratory rats.

This clearly presents a contradiction in logic. The conclusion states that it is genetical modification, that causes problems. But in fact choice A deviates from this reasoning and states, that the potato itself is at blame.

VerbalBot · Answer

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