## #4 - The song of the yellow warbler signals to other yellow

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Complete Question Explanation

Assumption. The correct answer choice is (C)

Due to the verbose nature of stimulus, it is important to isolate the essential elements that form the
structure of the argument:

Premise: Yellow warblers sing special songs when molting.

Premise: The special song deters other yellow warblers from encroaching upon the
territory of the molting warbler.

Conclusion: A molting warbler has no competition for food within its territory.

Because this is an assumption question, the answer you select must contain a statement upon which
the argument depends, i.e. a statement that is necessary for the conclusion to be true. All we know
from the premises is that other warblers will not enter the territory of the singer: that alone does not
preclude other birds from competing with the singing warbler for food.

Typically, if you see a major weakness in the argument, look for a Defender assumption answer
stating that the particular weakness does not exist. In other words, the author must be assuming that
no birds other than yellow warblers will compete with the molting warbler for food in its area. This
prephrase reveals answer choice (C) to be correct.

Answer choice (A): Whether the core area contains enough food to sustain the molting warbler is
irrelevant to the conclusion, which is about whether the warbler faces any competition for the food
supply within that area.

Answer choice (B): Whether or not other molting birds can lay claim to the feeding territory of the
singer is irrelevant to determining whether the singer would face competition for food in that area.

Answer choice (C): This is the correct answer choice, as it agrees with our prephrase. If this
answer is troubling you, use the Assumption Negation Technique and ask yourself if the following
statement would undermine the argument:

There are birds other than yellow warblers that compete with yellow warblers for food.

This clearly shows that the author’s conclusion is flawed and weakens her argument. Therefore,
answer choice (C) is an assumption upon which the argument depends.

Answer choice (D): This answer choice may seem attractive, because it supports the idea that yellow
warblers would face no competition for food in their feeding area: the other kinds of birds simply do
not eat the same kinds of food as warblers do. Although this statement supports the conclusion of the
argument, it is not necessary for the conclusion to be true. Even if the other birds ate the same kinds
of food as warblers do, that does not prove that warblers would face competition in their feeding
area, and therefore does not weaken the conclusion of the argument.

Answer choice (E): The relative size of the core areas of each warbler’s feeding territory has no
bearing on whether warblers face competition for food. This answer choice falls outside the scope of
the argument and is therefore incorrect.
douglajo
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I didn't like any of the answers on this question. Though C is the right answer, I'm not convinced of its being necessary.

To disprove it, imagine shrikes compete with yellow warblers for food when the yellow warblers are not molting. However, shrikes recognize when yellow warblers are molting and stay away (maybe molting yellow warblers are aggressive). This would allow there to be a bird that competes with the yellow warbler for food, but still allows for the conclusion of the argument to be true.

What am I missing?
Jason Schultz
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Hi douglajo,

Your hypothetical situation introduces a new element to the problem that the author isn't concerned with. The author doesn't mention competition from any other birds, so introducing them into an assumption question is a mistake.

When you say you are trying to "disprove" the assumption, I think you may be misunderstanding the assumption negation technique. When you use assumption negation, you are turning the problem into a weaken question, and in a weaken question you accept the answer choices as true.

So, negating answer choice C gives you "There are birds other than yellow warblers that compete with yellow warblers for food." This would seriously undermine the author's conclusion that "Yellow warblers...have no competition for the food supply..."

(For other readers, we are discussing Dec 2008 sec 2, #4)
douglajo
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Jason,

Thank you for your help so far! I agree that answer choice C allows conclusion to be drawn. In fact, if this were a justify question I would love (maybe even be in love with) answer choice C. However, I still don't see why the assumption is necessary.

Maybe if I breakdown my logic more explicitly, you can show me where I'm going awry:
1. We know yellow warblers might compete with each other for food when they are not molting based on the first two sentences of the stimulus.
2. We know that yellow warblers do not compete with each other for food when they are molting based on the third sentence.
3. We conclude that yellow warblers have no competition for food while they are molting. (I have taken the fact that the stimulus refers to the restricted range of flying to be synonymous with a period of molting. Is this an error?)

Answer choice C basically says that other birds never compete with yellow warblers for food. I'm not buying this because I think the conclusion is referring only to times when the yellow warblers are molting. In this respect, I do not think C is a necessary assumption, though it is sufficient. I would be fine with C if it said something like "no other birds compete with the yellow warbler for food while they are molting."

Can you elaborate on why it is necessary that other birds never compete with the yellow warbler for food, while the conclusion only seems to be concerned with the period during the wablers' molting?
David Boyle
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douglajo wrote:Jason,

Thank you for your help so far! I agree that answer choice C allows conclusion to be drawn. In fact, if this were a justify question I would love (maybe even be in love with) answer choice C. However, I still don't see why the assumption is necessary.

Maybe if I breakdown my logic more explicitly, you can show me where I'm going awry:
1. We know yellow warblers might compete with each other for food when they are not molting based on the first two sentences of the stimulus.
2. We know that yellow warblers do not compete with each other for food when they are molting based on the third sentence.
3. We conclude that yellow warblers have no competition for food while they are molting. (I have taken the fact that the stimulus refers to the restricted range of flying to be synonymous with a period of molting. Is this an error?)

Answer choice C basically says that other birds never compete with yellow warblers for food. I'm not buying this because I think the conclusion is referring only to times when the yellow warblers are molting. In this respect, I do not think C is a necessary assumption, though it is sufficient. I would be fine with C if it said something like "no other birds compete with the yellow warbler for food while they are molting."

Can you elaborate on why it is necessary that other birds never compete with the yellow warbler for food, while the conclusion only seems to be concerned with the period during the wablers' molting?

Hello douglajo,

Let me try to add to some of the valuable things Jason said (though I can't read his mind and know exactly what he meant, of course). I think that answer choice C was not written as well as it could have been, and your proposal of adding "while they are molting" is a somewhat helpful proposal. It may make things a little clearer.
However: 1) maybe LSAC is just trying to make things difficult here, and 2) even if they weren't, they slip and fall and make mistakes sometimes. So overall, C is a pretty good answer, certainly better than any of the others!
In a broad sense, all creatures are always competing with each other for food. Because of the hamburger I ate last night, some tiger wasn't able to eat that cow, say. (Do tigers eat cows? ...Hmm) But I think the passage is about competition within the narrow sphere of warblers' particular feeding sphere etc., so again, C is a pretty good, if imperfect, answer.
Hope that helps,

David