Tiger beetles are such fast runners - CR

[Guest]

Tiger beetles are such fast runners that they can capture virtually any nonflying insect. However, when running toward an insect, a tigerbeetle will intermittently stop and then, a moment later, resume its attack. Perhaps the beetles cannot maintain their pace and must pause for a moment's rest; but an alternative hypothesis is that while running, tiger beetles are unable to adequately process the resulting rapidly changing visual information and so quickly go blind and stop.

Which of the following, if discovered in experiments using artificially moved prey insects, would support one of the two hypotheses and undermine the other?

A When a prey insect is moved directly toward a beetle that has been chasing it, the beetle immediately stops and runs away without its usual intermittent stopping.
B In pursuing a swerving insect, a beetle alters its course while running and its pauses become more frequent as the chase progresses.
C In pursuing a moving insect, a beetle usually responds immediately to changes in the insect's direction, and it pauses equally frequently whether the chase is up or down an incline.
D If, when a beetle pauses, it has not gained on the insect it is pursuing, the beetle generally ends its pursuit.
E The faster a beetle pursues an insect fleeing directly away from it, the more frequently the beetle stops.



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I chose B, as it weakens the claim that they can not adequately process the rapidly changing visual info ('a beetle alters its course while running') and supports the other hypothesis - that they can not maintain their pace ('pauses become more frequent'). But the OA is C. Any insight will be appreicated.
Thanks.

[editor: the correct answer to this problem is (b), not (c). see later posts.]

[Guest]

Choice B should read- In pursuing a moving insect, the beetles usually respond immediately to changes in the insect's direction, and pause equally frequently whether the chase is up or down an incline.

The phrase usually respond immediately to changes in the insect's direction in choice B does not weaken the second hypothesis enough. The term usually as used leaves it open to the possibility that the tiger beetles may or may not be unable to process the resulting rapidly changing visual info., and so quickly go blind and stop. In other words, it could mean that there are times in which tiger beetles respond immediately and there are times they do not.

Choice C should read-The beetles maintain a fixed time interval between pauses, although when an insect that had been stationary begins to flee, the beetle increases its speed after its next pause.
On the other hand, Choice C strengthens the second hypothesis it reaffirms what has been stated that the tiger beetle cannot process rapidly changing visual information, since it increases it's speed after its next pause not immediately after the insect begins to flee.

[Guest]

Is this the same question as the one in the 11th edition orange guide (D25)?

According to OG, B is the correct answer. Even if it is a different question, why is B correct above but not here?

B In pursuing a swerving insect, a beetle alters its course while running and its pauses become more frequent as the chase progresses.

p. 83: This statement provides info that strengthens the scond hypothesis: the swerving pursuit and the resulting continual course adjustments appear to be forcing the bettle to stop with increasing frequency to sort out the erratic visual information.

[sanjaylakhani]

Hi Ron

i am confused with C answer choice- it seems to undermine both theories - if insect can respond immi to changing directons , it shows he has no issue with visual- and he pauses equally frequently - shows that the pause has nothing to do with exertion- as correctly mentioned by you

while B seems to undermine only one theory- B says that insect can move almost immi and takes more pauses - which makes it clear that the insect pauses because of exhaustion and nt because of visual issues....

[RonPurewal]

[quote="RR"](b) supports one hypothesis - the fatigue hypothesis, as mentioned above.
it also undermines the blindness hypothesis, because, unless the insect is swerving with increasing frequency as the chase progresses (something which we've no reason to assume), that hypothesis would predict that it would pause with a roughly constant frequency (whenever the swerving caused it to become disoriented).

[redable]

here's another "Tiger beetles" question came from GMATPrep:

Tiger beetles are such fast runners that they can capture virtually any nonflying insect. However, when running toward an insect, the beetles intermittently stop, and then, a moment later, resume their attack. Perhaps they cannot maintain their pace and must pause for a moment's rest; but an alternative hypothesis is that while running tiger beetles are unable to process the resulting rapidly changing visual information, and so quickly go blind and stop.

Which of the following, if discovered in experiments using artificially moved prey insects, would support one of the two hypotheses and undermine the other?

(A) When a prey insect is moved directly toward a beetle that has been chasing it, the beetle immediately turns and runs away without its usual intermittent stopping.
(B) In pursuing a moving insect, the beetles usually respond immediately to changes in the insect's direction, and pause equally frequently whether the chase is up or down an incline.
(C) The beetles maintain a fixed time interval between pauses, although when an insect that had been stationary begins to flee, the beetle increases its speed after its next pause.
(D) If, when a beetle pauses, it has not gained on the insect it is pursuing, the beetle generally ends its pursuit.
(E) When an obstacle is suddenly introduced just in front of running beetles, the beetles sometimes stop immediately, but they never respond by running around the barrier.


The words with different color are differed from the question from OG11th

OA: C,
but I chose incorrect E
why C is correct?

Thanks in advance :)

[tim]

C is correct because keeping a fixed interval supports the visual processing hypothesis and undermines the rest hypothesis. If the pauses are needed to get a visual fix, it makes sense that the intervals would be fixed because the time needed to get a visual fix shouldn't change. However, if the beetles need to pause for rest, they should need longer pauses after they start moving faster..

Interesting to see that there is a new version of this problem. The original one from the OG had some severe problems..

[gmatwork]

In original question choice (c) - Doesn't this choice undermine both the hypotheses?

[RonPurewal]

In original question choice (c) - Doesn't this choice undermine both the hypotheses?

yes.
the answer to the original is (b), not (c). please read the whole thread!

[gmatwork]

How does choice (b) undermine vision hypothesis? I don't really get that.

[RonPurewal]

How does choice (b) undermine vision hypothesis? I don't really get that.

if the beetle can "alter its course while running", it can be inferred that the beetle doesn't go blind while running. if it went blind, it wouldn't be able to alter its course.

[keithyang926]

How does choice (b) undermine vision hypothesis? I don't really get that.

if the beetle can "alter its course while running", it can be inferred that the beetle doesn't go blind while running. if it went blind, it wouldn't be able to alter its course.

Sorry to dig up this topic(the original beetle question) again. I just got pretty confused by the explanation for this question in OG13.
When I was first working on it, I chose B, because B supports the first and weakens th second; C undermins both hypotheses. But OG explanation for B is "This statement provides information that strengthens the second hypothesis: the swerving pursuit and resulting continual course adjestments appear to be forcing the beetle to stop with increasing frequency to sort out the erratic visual information."

This description talks about the oppsite of my view and its reasoning part confounds me, but my thoughts of answer B seems to be confirmed in this thread. So, does this mean that I could question what the OG says here? Or am I missing any point?

Ron, or anyone else can help?

Thanks!

[RonPurewal]

How does choice (b) undermine vision hypothesis? I don't really get that.

if the beetle can "alter its course while running", it can be inferred that the beetle doesn't go blind while running. if it went blind, it wouldn't be able to alter its course.

Sorry to dig up this topic(the original beetle question) again. I just got pretty confused by the explanation for this question in OG13.
When I was first working on it, I chose B, because B supports the first and weakens th second; C undermins both hypotheses. But OG explanation for B is "This statement provides information that strengthens the second hypothesis: the swerving pursuit and resulting continual course adjestments appear to be forcing the beetle to stop with increasing frequency to sort out the erratic visual information."

This description talks about the oppsite of my view and its reasoning part confounds me, but my thoughts of answer B seems to be confirmed in this thread. So, does this mean that I could question what the OG says here? Or am I missing any point?

Ron, or anyone else can help?

Thanks!

in my experience, about 5% of o.g. explanations are wrong. most wrong explanations i've seen are in sentence correction; some of them are pretty blatant. (in og12 #77, for instance, the explanation identifies two constructions that aren't parallel, but simply have the same form by coincidence, as parallel structures.)

this could be one of them.
in any case, it's clear that gmac's all-stars write the questions but don't also write the explanations; that latter job is left to their "B-team", so to speak. (this situation is of course better than the other way around!)

[yqren2002]

I just don't understand why C is wrong in the original question.

Someone mentioned C undermined both.

My understanding is:

"usually responds immediately to changes" undermined the vision hypothesis.

"pauses equally frequently" strengthened the fatigue hypothesis. Yes I agree that the frequency to stop and have a rest should increase if the insect runs faster but we are not given that insect is moving faster. It is reasonable to think that "pauses equally frequently" is caused by fatigue.

I understand that B is correct because fatigue COULD also cause the beetle to pause more frequently when chase continues.

But the beetle could also stop equally frequently to have a rest when the chase is up or down, couldn't it?? Please let me know why C is not correct. Thanks!

[tim]

i think the idea is that if fatigue were an issue, the beetles would get more fatigued going up an incline than going down, thus the length of pauses would be different. hence the fact that the pauses are the same undermines the hypothesis..