Q4 - The song of the yellow

[ManhattanPrepLSAT1]

I like your instincts on this one, but it does need to be true that there are no birds that compete with the yellow warbler for food. Otherwise, we would not be able to establish that the yellow warbler has no competition for food in the restricted flying range.

If there were some birds who compete for food with the yellow warbler, than it would not be possible to establish the conclusion based on the evidence.

Here's something very important to applying the Negation Test on Necessary Assumption questions. We're not just looking for something that is necessary to the conclusion, but necessary to the reasoning of the argument. Ruling out other yellow warblers would not permit one to conclude that yellow warblers who are molting have no competition for food, unless we also rule out other possible competitors as well. So when you apply the Negation Test, don't just ask yourself whether the conclusion has been destroyed, ask yourself whether the reasoning has been destroyed.

Answer choice (C) needs to be true in order for the elimination of other yellow warblers to justify the claim that molting yellow warblers have no competition for food.

Let's look at the incorrect answer choices:

(A) is not needed since the argument never claims that there is enough food for the molting yellow warbler, just that it faces no competition.
(B) is irrelevant. This could be a characteristic of other birds as well.
(D) supports the conclusion, but need to be true in order for the argument's reasoning to follow. Additionally, this answer choice permits the possibility that sometimes these other birds do compete with yellow warblers, which would then undermine the argument.
(E) is irrelevant. The size of the core feeding area need not always be the same. There could be factors such as climate and terrain that impact the size of the core feeding area that warblers all seem to recognize.

Hope that helps!


#officialexplanation

[weiyichen1986]

Hey, i was choosing between C and D, and finally choose D on this one.

The reason i did not pick C is because C seems a bit of too extreme, do we really need " no bird" as a necessary condition? If there are some birds, but as long as they are within the range of their restriced flying, there will also no competition.....

Thanks for help !!!

[johnsdouglass]

I didn't like any of the answers on this one. To me, C seems just as wrong as any of the others. Imagine shrikes nominally compete with yellow warblers for food. 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?

[ManhattanPrepLSAT1]

Hey John, I see your point. But that relies on an additional assumption -- a potential competitor recognizes the molting warbler and stays away.

Suppose we just look at what happens if answer choice (C) is not true -- there are birds other than yellow warblers that compete for food with yellow warblers. Not taking any further assumptions into consideration, doesn't that pose a challenge to the argument?

Essentially, we need to find an assumption that the argument (as stated, without further assumptions) relies on. Since the argument never discussed the possibility that other competing birds would stay away, only that other yellow warblers will not entire the core territory, we should not take that possibility into consideration.

Hope that helps!

[Mab6q]

Am I right in thinking that there is another big assumption in this question besides C. Is the author assuming that the range of the area during restricted flying is equivalent to smaller core territory... Are they the same? To me, i dont think so. I think the latter refers to the areas that the other birds wont come one, and the former refers to the area that they can fly. So, if the bird can fly outside of the smaller core territory, then it can get food there, and as such there can be competition. Please let me know if that makes no sense.

I understand why C is right but just wanted to see if I was right in identifying both flaws. Thanks you.

[eve.lederman]

I'm still not sure why we eliminate D. If we negate it (warblers share their feeing areas with other bird, which DO eat the same foods as warblers), wouldn't that weaken the author's conclusion, meaning that D is the correct answer?
The only reason I can think to eliminate it is because we don't know about the other birds' behavior during molting time.
I'd appreciate any clarification! Thanks!

[ohthatpatrick]

To answer the question from two posts ago, yes, I think you're right. We don't have to accept that "can only fly short distances" = "can only fly within the smaller core territory".

The short distances could easily match the smaller core territory, be bigger, or be smaller.

The author needs to assume that the distance the yellow warbler can fly during molting is at most as far as the radius of its smaller core territory.

===

As to negating (D), it's a tricky sentence to negate.

Rememer, negations are the same as prefacing an answer choice with "it is NOT true that".

(D) talks about birds who don't eat the same food as YW's.

If we negate (D), we'll simply be saying that what we previously said about birds who don't eat the same food as YW's is not true.

That doesn't mean we'll suddenly be talking about birds who DO eat the same food as YW's.

Suppose this was (D):
(D) Sam often shares his hamburger with black cats.

If you negate that sentence, is Sam suddenly sharing his hamburger with brown cats or white cats or yellow cats?

No. You're just saying "It's not true that Sam often shares his burger with black cats."

You could rephrase that as "Sam rarely, if ever, shares his hamburger with black cats."

But no negation will suddenly make that statement about OTHER types of food besides hamburgers or OTHER types of cats besides black cats.

So the negation of (D) is simply that "Warblers do NOT often share their feeding areas with other birds, which eat a different diet than the warblers do."

Whether the warblers often share their area with differently-eating birds or whether they DON'T OFTEN share their area with those type of birds is irrelevant.

Pretend I say "I often have lunch with Republicans, who often support military intervention."

If we negate that, we're not saying that I regularly have lunch with pacifistic Republicans. The negation would be that "I do NOT often have lunch with Republicans." The descriptive clause at the end of the sentence just gives us more information about the noun "Republicans". The truth value of the sentence, though, hinges on whether or not I perform an action on that original noun.

Hope this helps.

[eve.lederman]

that does help, thanks! i was just negating the wrong part of it. so by saying that warbles don't share their food, that either does nothing or strengthens the conclusion, which is why it's incorrect. thanks again!

[contropositive]

I thought D was out of scope because it doesn't guarantee that the molting bird doesn't have any competition. It leaves the possibility that maybe the other birds do eat the same insects or seeds when the bird is molting, in that case the molting bird does have competition.

I am confused about A. During review I picked C and I see why C is right but during timed test I picked A because if there is just enough food for the molting bird then doesn't that guarantee that other birds won't compete with the molting bird for food? Is A wrong because it doesn't close the possibility that perhaps other birds don't know that their is enough food for molting bird? For example, would A be correct if it said "other birds know that the core areas contain just enough food to sustain one yellow warbler while it molts?"

[ohthatpatrick]

You seem to be thinking of this question as Sufficient Assumption, because your analysis of the answers is based on whether each answer choice, if true, would guarantee the conclusion.

But this is NOT Sufficient Assumption. The question stem does not ask which of the following answers would PROVE the conclusion.

This is Necessary Assumption. You can't test these answers by asking
if true, would it prove the conclusion? (that's how you test Sufficient)

You test Necessary Assumption answer choices by asking
if false, would it badly weaken the argument?
(that's the whole idea of the Negation Test)

So try (A), (C), and (D) again with this question in mind
"Which of these, if false, would most weaken?"

(A), if negated, says that the core areas contain more than the minimum amount of food to keep one warbler alive.

Does that hurt the conclusion that "during molting, yellow warblers have NO competition for the food supply in their core area"?

Not really. Sure, we would know that there is more food in the core area than what the single warbler needs, but we still have no idea who is going to try and eat that food besides the molting warbler.

(D), if negated, says that in the core area of a warbler, there is usually NOT other kinds of birds who eat a different diet than warbler-food.

If these birds do NOT eat warbler-food, then who cares whether they are/aren't in the core area? That couldn't weaken the argument.

(C), if negated, says that there ARE other birds beside warblers that compete for warbler-food. Does that hurt the conclusion that "during molting, yellow warblers have NO competition for the food supply in their core area"?

It does. The argument made us confident that a fellow yellow warbler would never dare to intrude on a molting warbler's core area. But we never got any guarantees about OTHER types of birds barging in on the core area during molting time.

It may seem like it's not the most powerful weakener, because all you're saying is that there are SOME other birds competing with the warbler for food.

However, when an author concludes something very extreme, such as "There is NO competition for food", it takes very little to contradict him.

If someone claimed that "ALL girls like Justin Bieber", then I only need to produce one solitary example of a girl who does not like Justin Bieber in order to refute that argument.

========

You could literally do every single Necessary Assumption question by swapping in the question stem
"Which of the following, if false, would most weaken?"

Nobody DOES that, because negating every single answer can be exhausting (when it's often easier to just say, "The author wasn't talking about that and it doesn't matter to his argument"), but you should realize the only way to measure whether a Necessary Assumption answer choice does the job is to negate it and see if the argument is badly weakened (many correct answers, when negated, pretty much sound like you're contradicting the conclusion!)

Hope this helps.

[kristinfabella]

I chose (C) because it seemed better than all of the other answer choices. I understand why it's correct, but I was at first hesitant to choose it because of one thought.

It says "There are no birds other than yellow warblers that compete with yellow warblers for food."
But what if there are other animals that may compete with yellow warblers for food?

We could rule out yellow warblers as competitors, but what if there was another type of animal? Therefore, could we still conclude there is "NO competition" for the food supply?

I'm thinking that my question about other animals is out of scope; please let me know how to go about this. Thanks!

[AshleighT608]

Should we assume that anytime the LSAT asks for an assumption it is asking for a necessary assumption? And when it asks for an assumption upon which the argument is required or proves... should we assume it is asking for a sufficient assumption?

Thanks!

You seem to be thinking of this question as Sufficient Assumption, because your analysis of the answers is based on whether each answer choice, if true, would guarantee the conclusion.

But this is NOT Sufficient Assumption. The question stem does not ask which of the following answers would PROVE the conclusion.

This is Necessary Assumption. You can't test these answers by asking
if true, would it prove the conclusion? (that's how you test Sufficient)

You test Necessary Assumption answer choices by asking
if false, would it badly weaken the argument?
(that's the whole idea of the Negation Test)

So try (A), (C), and (D) again with this question in mind
"Which of these, if false, would most weaken?"

(A), if negated, says that the core areas contain more than the minimum amount of food to keep one warbler alive.

Does that hurt the conclusion that "during molting, yellow warblers have NO competition for the food supply in their core area"?

Not really. Sure, we would know that there is more food in the core area than what the single warbler needs, but we still have no idea who is going to try and eat that food besides the molting warbler.

(D), if negated, says that in the core area of a warbler, there is usually NOT other kinds of birds who eat a different diet than warbler-food.

If these birds do NOT eat warbler-food, then who cares whether they are/aren't in the core area? That couldn't weaken the argument.

(C), if negated, says that there ARE other birds beside warblers that compete for warbler-food. Does that hurt the conclusion that "during molting, yellow warblers have NO competition for the food supply in their core area"?

It does. The argument made us confident that a fellow yellow warbler would never dare to intrude on a molting warbler's core area. But we never got any guarantees about OTHER types of birds barging in on the core area during molting time.

It may seem like it's not the most powerful weakener, because all you're saying is that there are SOME other birds competing with the warbler for food.

However, when an author concludes something very extreme, such as "There is NO competition for food", it takes very little to contradict him.

If someone claimed that "ALL girls like Justin Bieber", then I only need to produce one solitary example of a girl who does not like Justin Bieber in order to refute that argument.

========

You could literally do every single Necessary Assumption question by swapping in the question stem
"Which of the following, if false, would most weaken?"

Nobody DOES that, because negating every single answer can be exhausting (when it's often easier to just say, "The author wasn't talking about that and it doesn't matter to his argument"), but you should realize the only way to measure whether a Necessary Assumption answer choice does the job is to negate it and see if the argument is badly weakened (many correct answers, when negated, pretty much sound like you're contradicting the conclusion!)

Hope this helps.

[ohthatpatrick]

Should we assume that anytime the LSAT asks for an assumption it is asking for a necessary assumption?


It wouldn't kill ya, even though it's not technically a guarantee. In 99.5% of cases where the word ASSUMPTION or ASSUMING is used in the question stem, it's Necessary Assumption.

But you could write a Sufficient Assumption question stem that would use that word:
f.e. Which of the following is an assumption that would allow the conclusion to follow logically? would be Sufficient Assumption.

And when it asks for an assumption upon which the argument is required or proves... should we assume it is asking for a sufficient assumption?


REQUIRED vs. PROVES is the essence of NECESSARY vs. SUFFICIENT, so, no, definitely don't conflate those.

NECESSARY
which is an assumption on which the argument depends
which assumption is required
which needs to be assumed
what is the author assuming
what must be assumed

SUFFICIENT
which, if assumed, allows the conclusion to follow logically
which, if assumed, allows the conclusion to be properly drawn
which, if assumed, allows the conclusion to be properly inferred


Remember the difference in meaning between the two tasks:
SUFF ASSUMP: which answer, if added to the evidence, fully proves the conclusion?
NEC ASSUMP: which answer, if negated, most weakens the argument?