Capuchin Monkeys in Venezula

[Saurabh Malpani]

Capuchin monkeys in Venezuela often rub a certain type of millepede into their fur. Secretions of these millipedes have been shown to contain two chemicals that are potent mosquito repellents, and mosquitoes carry parasites that debilitate the capuchins. The rubbing behavior is rare except during the rainy season, when mosquito populations are at their peak. Therefore monkeys probably rub millipedes into their fur only because doing so helps protect them against mosquitoes.
Which of the following would be most useful to determine in order to evaluate the argument.

A) Whether the two chemicals provide any protection for millipedes against their own repellents.
B) Whether the type of millipede used by the capuchin monkeys in Venezuela is found in other parts of the world.
C) Whether animals other than capuchins rub insects of any kind into their fur
D) Whether the only time millipedes are readily available to capuchins is during rainy season
E) Whether secretions of any other insects accessible to capuchins contain chemicals that repel the mosquitoes"

Source GMAT Prep

Question: Can you please reason out D/E.


The correct answer is : E

I tried negation and was able to derive at an answer but was still now sure.

MGMAT tutors please help.

Thanks
Saurabh Malpani

[Guest]

Ron:

I am still confused as to why (A) is irrelevant. The conclusion of the argument is monkeys probably rub millipedes into their fur only
because doing so helps protect them against mosquitoes.

A) Whether the two chemicals provide any protection for millipedes against their own repellents.

If they do not provide any protection, then the argument is weakened. (probably they are doing so for some other reason)
If they provide some protection, then the argument is strengthened.

thanks for your help.

[RonPurewal]

Ron:

I am still confused as to why (A) is irrelevant. The conclusion of the argument is monkeys probably rub millipedes into their fur only
because doing so helps protect them against mosquitoes.

thanks for your help.

that's correct: the conclusion of the argument is that the monkeys rub the millipedes into their fur because the monkeys are thereby protected against mosquitoes.

choice a deals with whether the millipedes themselves are protected against chemicals, a consideration that is irrelevant to the situation of the monkeys.

[saurabh_malpani]

Yes I am sorry the correct answer is indeed D. I must have typed it wrong!

Sorry for the confusion!
Saurabh Malpani

[editor: deleted some previous posts that contained misinformation.]

[sd]

Ron, can you please explain between D and E which is the correct answer and why? I read your explanations and thought E was the best but then the OA is posted as D in subsequent posts. Which is correct..? I am freaking out seeing such confusing CRs and have my GMAT in a week...please help

[RonPurewal]

Ron, can you please explain between D and E which is the correct answer and why? I read your explanations and thought E was the best but then the OA is posted as D in subsequent posts. Which is correct..? I am freaking out seeing such confusing CRs and have my GMAT in a week...please help

ok. after doing a bit more research into these types of questions, we have a more systematic approach to them.

if you see "Which of the following would be most useful to determine in order to evaluate the argument", then you should think of the same sorts of things you'd consider in a STRENGTHEN/WEAKEN problem.
the only difference is that the statements will contain indeterminate words, such as "whether", instead of actually saying that something does or doesn't happen. this is why these problems aren't really "strengthen" or "weaken"; most of t hem are situations in which "does happen" would be "strengthen" and "doesn't happen" would be "weaken", or vice versa.

--

so, let's think about this as a STRENGTHEN/WEAKEN QUESTION.

when you consider STRENGTHEN/WEAKEN problems, you should SIMPLIFY THE ARGUMENT as much as possible.

in this problem, the argument basically boils down to
they only rub the millipedes during the rainy season.
during the rainy season, there are more mosquitoes than usual.
therefore, the rubbing must have to do with mosquitoes.

the weak link in this argument is the assumption that there's no OTHER connection between the rubbing and the rainy season.
in other words, the argument assumes that because both of these ideas are connected to the mosquitoes, the mosquitoes MUST be responsible for the overall connection.

therefore,
if an answer choice gives ANOTHER connection between the rubbing and the rainy season, then it weakens the argument.

choice (d) does this: it's another reason why the rubbing might be connected to the rainy season, a reason that has nothing at all to do with mosquitoes.

choice (e) doesn't really help unless there's some connection to the rainy season (which is the crux of the argument). whether or not there are such alternate insects, it doesn't really matter unless they would have differential effects during the rainy season vs. non-rainy season.

[vgirotra]

A great breakdown of this question by Stacey at BTG:

http://www.beatthegmat.com/mba/2011/01/18/breaking-down-a-gmatprep-cr-evaluate-a-conclusion-problem

[RonPurewal]

A great breakdown of this question by Stacey at BTG:

http://www.beatthegmat.com/mba/2011/01/18/breaking-down-a-gmatprep-cr-evaluate-a-conclusion-problem

thanks for the linkage.

[harishmullapudi]

therefore,
if an answer choice gives ANOTHER connection between the rubbing and the rainy season, then it weakens the argument.

choice (d) does this: it's another reason why the rubbing might be connected to the rainy season, a reason that has nothing at all to do with mosquitoes.

choice (e) doesn't really help unless there's some connection to the rainy season (which is the crux of the argument). whether or not there are such alternate insects, it doesn't really matter unless they would have differential effects during the rainy season vs. non-rainy season.[/quote]


I think the correct answer choice for this question is E. Can you please confirm this.

[harishmullapudi]

I think the correct answer choice for this question is E. Can you please confirm this.

I choose D when i was doing this question, but some people said it was E. So I looked again at E option and thought even E can be the answer. My view is...

"Whether secretions of any other insects accessible to capuchins contain chemicals that repel the mosquitoes."

Lets say that reason is true.. means... Secretions of any other insects accessible to capuchins contain chemicals that repel the mosquitoes. So capuchins neednot use millipedes to protect itself from mosquitoes.

let say the reason is false... means... Secretions of any other insects accessible to capuchins do not contain chemicals that repel the mosquitoes. So capuchins must use millipedes to protect themselves from mosquitos.



Is my view correct? can you please explain?

[RonPurewal]

Lets say that reason is true.. means... Secretions of any other insects accessible to capuchins contain chemicals that repel the mosquitoes. So capuchins neednot use millipedes to protect itself from mosquitoes.

This is not relevant.
You're thinking about whether the monkeys have to use this particular millipede. The passage, on the other hand, is not concerned with necessity; it's concerned only with why the monkeys do use that millipede.

Analogy:
The liquor that Tom drinks, unlike wine, has no cardiovascular benefits. Therefore, Tom only drinks that liquor in order to get drunk.

--> Your objection here is like saying, "Well, what if there are other things that will also get Tom drunk?"
Hopefully you can see why that's not actually an objection here.

[benjamindian]

Ron, can you please explain between D and E which is the correct answer and why? I read your explanations and thought E was the best but then the OA is posted as D in subsequent posts. Which is correct..? I am freaking out seeing such confusing CRs and have my GMAT in a week...please help

ok. after doing a bit more research into these types of questions, we have a more systematic approach to them.

if you see "Which of the following would be most useful to determine in order to evaluate the argument", then you should think of the same sorts of things you'd consider in a STRENGTHEN/WEAKEN problem.
the only difference is that the statements will contain indeterminate words, such as "whether", instead of actually saying that something does or doesn't happen. this is why these problems aren't really "strengthen" or "weaken"; most of t hem are situations in which "does happen" would be "strengthen" and "doesn't happen" would be "weaken", or vice versa.

--

so, let's think about this as a STRENGTHEN/WEAKEN QUESTION.

when you consider STRENGTHEN/WEAKEN problems, you should SIMPLIFY THE ARGUMENT as much as possible.

in this problem, the argument basically boils down to
they only rub the millipedes during the rainy season.
during the rainy season, there are more mosquitoes than usual.
therefore, the rubbing must have to do with mosquitoes.

the weak link in this argument is the assumption that there's no OTHER connection between the rubbing and the rainy season.
in other words, the argument assumes that because both of these ideas are connected to the mosquitoes, the mosquitoes MUST be responsible for the overall connection.

therefore,
if an answer choice gives ANOTHER connection between the rubbing and the rainy season, then it weakens the argument.

choice (d) does this: it's another reason why the rubbing might be connected to the rainy season, a reason that has nothing at all to do with mosquitoes.

choice (e) doesn't really help unless there's some connection to the rainy season (which is the crux of the argument). whether or not there are such alternate insects, it doesn't really matter unless they would have differential effects during the rainy season vs. non-rainy season.

Hi Ron, I chose D but my reasoning is the opposite....

in this problem, the argument basically boils down to

Monkeys only rub the millipedes during the rainy season
during the rainy season, there are more mosquitoes than usual
And we are also told that rubbing millipedes will produce some chemicals that keep away mosquitoes which are harmful for monkeys -->so monkeys actually benefit from rubbing millipedes
Then the author concludes that the rubbing probably have to do with mosquitoes.

Choice D: if the only time the millipedes are readily available to monkeys is during the rainy season when there are many mosquitoes, then those monkeys will take advantage of the millipedes to keep away the mosquitoes because there are so many. So this reasoning strengthens the conclusion that "the monkeys probably rub the millipedes into their fur because doing so helps protect them against mosquitoes".

If the millipedes are available throughout the year when there are still mosquitoes around, but we are told that "the rubbing behavior is rare except during the rainy season", then the monkey might rub millipedes for other reasons (maybe there are other bugs/factors during the raining season but it's not because of the mosquitoes). And this reasoning will actually weaken the author's prediction since the rubbing is probably not for mosquitoes.

Please let me know whether my reasoning is correct. Thanks.

[NurB544]

Therefore monkeys probably rub millipedes into their fur only because doing so helps protect them against mosquitoes.
concentrate on the part of sentence! ***rare behavior- rub millipedes *** why they rub? is it rare behavior? what happen if secretions of any other insects accessible to capuchins contain chemicals that repel the mosquitoes? will they rub other insects ? if not it is not rare behavior! if yes, we will know it is new behavior! so E)
E) Whether secretions of any other insects accessible to capuchins contain chemicals that repel the mosquitoes"

[RonPurewal]

NurB544, do you have a question? I can't tell.

Please clarify, thanks.

[JbhB682]

Hi Experts - chose E unfortunately. Here was my thinking :
Yes - weakened
No - strengthened.

E - If Yes [yes - secretions of other insects accessible to capuchins contain chemicals that repel the mosquitoes]

This possibility weakens the conclusion (I think ?) because if there are other options available to the capuchin monkey for the purposes of repealing mosquitos (he can rub other insects other than millipedes , why is the monkey still rubbing millipedes during the rain in that case (when there are alternatives the monkey can rub on itself for the purposes of repealing mosquitos during the rain) ?

He prefers the millipedes over other insects for repealing mosquito's

This weakens the conclusion I think ? [@Emily - feel free to let me know if I made any wrong assumptions as I reasoned through this branch]

E - If no [Secretions of other insects accessible to capuchins don't contain chemicals that repel the mosquitoes]

if secretions of other insects don't repel mosquitoes but the secretion of the millipede does repel mosquito's -- this strengthens the hypothesis put forward by the author [hypothesis being --- we know the secretions of the millipede do repeal mosquitos and we see monkey rubbing themselves with these millipedes when it rains, thus the hypothesis is monkeys rub millipedes for the purposes of repealing mosquitos only]

I thought this hypothesis was strengthened by eliminating other ways monkey can repeal the mosquito.

I am pretty sure there is a gap somewhere in my thinking.