Tiger beetles are such fast runners that they can capture virtually an

Question

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.
Theory1: Perhaps they cannot maintain their pace and must pause for a moment's rest;
Theory2: while running tiger beetles are unable to process the resulting rapidly changing visual information, and so quickly go blind and stop.

can someone explain why B is wrong and C is right?

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.

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Pauline · Accepted Answer

ОА  is C

Yes, this is a tough one.

Let's analize B and C (it's easy to eliminate A,D,E)
We have Theory 1: they pause to have rest
and Theory 2: they pause to process visual information

  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.  
=> The visual info is rocessed OK. Theory 2 is undermined. When you go down an incline - it's easier for you to go, so you need rest rarely. But here it is said that no matter up or down - the intervals are equal. Theory 1 is also undermined.

  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. 
=> Speed increases after pause - not after the insect begins to flee: that means that Theory 2 has a point - there's a problem with visual info. Intervals remain the same: speed_before*time < speed_after*time - the distance is greater, and the beetle is not tired. This undermines Theory 1.

Here it is, I think.

b9n920 · Answer

Hi, I would like to add my 2 cents, 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. - The beetle changes its direction readily in pursuing a moving insect: what we get from this? Probably Tiger Beetles (TB) got GOOD vision. Theory 2 ruled out. Fine. They pause equally frequently no matter chasing up or down. Conclusion? Maintaining pace is NO big deal. Going down definitely gives TB more pace than going up. Theory 2 also gone. But we got undermine any one of the theories. ELIMINATE. 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. - fixed time interval between pauses - this part supports that TB actually can't maintain too much pace(supports Theory 1). As if, TB got to stop after attaining X miles/hr speed. TB increases its speed as stationary insect begins to flee - TB has a great vision(Theory 2 undermined). C seems GOOD. I think its a fairly lengthy CR in terms of amount of thinking involved, a fact that the author utilized in devising a trick answer choice B, which is a great choice except for its undermining both the theories. :wink:

Binit.

priyankurml · Answer

IMO C.

Hypothesis1 is: tiger beetles are unable to adequately process the resulting rapidly changing visual information 
Hypothesis2 is: so quickly go blind and stop.

Only C states the scenario to support hypothesis1 but hurt hypothesis2. "responds immediately to changes in the insect’s direction" supports the hypothesis1 while ignores the blind issue.

In E whether beetle stops due to blindness or changing variation is not clear. Whereas C clearly states the cause.

chetan2u · Answer

Hi,
Just read few posts above yours and my understanding of C is slightly different....

C tells us that the beetles pause at regular intervals....
Say it pauses after 10 secs....
When the insect is stationary, it travels at a slower speed say 6m per minute so it travels 1 m and pauses..
Now the insect is fleeing and the beetle increases its speed to say 12m per minute...
Now it travels 2 m in 10 secs and then pauses..

BUT if the beetle was getting tired and taking rest it should have stopped after traveling 1 m in second case too that is after five seconds and not 10 seconds..

So it means the beetle stops to adjust its vision after regular intervals..

Nightmare007 · Answer

Lets decipher:

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.
Theory1: Perhaps they cannot maintain their pace and must pause for a moment's rest;
Theory2: while running tiger beetles are unable to process the resulting rapidly changing visual information, and so quickly go blind and stop.

can someone explain why B is wrong and C is right?

Tiger beetles stop intermittently in between while running.
1st theory : They stop because they become tired.
2nd Theory: While running tiger beetles are unable to process resulting rapidly changing information and 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.
They won't stop... This guy undermines both the theories. Both theories say they stop because X and because Y. A says they never stop. --- OUT

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.
They immediately respond to insects change in direction. - So they can process the information quickly cool. - Theory 2 is failing
They pause equally frequently whether the chase is up or down an incline- what the fish... So It is not because they become tired ? When running down the cliff they expend less energy so they should stop in NON-EQUAL intervals when compared to when they climb up. - So it is not because they become tired. - Theory 1 is failing - JUST last phrase kicks the option OUT. We need to read the whole option from now on..

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.
 Fixed time interval between pauses  -  OK nice they become tired at regular intervals when running. - Supporting Theory 1 
 Although when the insect that had been stationary begins to flee.  -  Wow they maintain fixed pauses even when the insect changes its direction and movement - Now It undermines Theory 2.

ANSWER

D If, when a beetle pauses, it has not gained on the insect it is pursuing, the beetle generally ends its pursuit.
wow nothing... It supports neither theory 1 nor theory 2 ... OUT
 
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.
SOMETIMES..... not a good one.. OUT

Prasannathawait · Answer

Indeed a nice question.
Between B and C we have to carefully read each word/phrase. 
'the beetles usually respond immediately to changes in the insect's direction' ----This undermines the second conclusion.
'Stops equally frequently when moving up or down' ------This undermines the first conclusion.

C is the answer.

TheNightKing · Answer

chetan2u

Hello Sir,
So I did read your explanation and it makes sense to me. But just for full proofing the argument , can you tell me, based on your analysis, which hypothesis is undermined and which one is supported?

I know a similar question exists and for which OA is B. That one clearly undermines one and supports another one. But this one is confusing.

davidbeckham · Answer

Bunuel  I think there are two such posts which two different OAs, could you please clarify which is the correct one?

Bunuel · Answer

There are two similar but different questions. The OA for the above question is C. The OA is B for the following one: https://gmatclub.com/forum/tiger-beetle ... 50947.html

Harsh2111s · Answer

TheNightKing Yes indeed it's a 750 level question, took 4 min to crack. Let's look at two arguments : the beetles intermittently stop, and then, a moment later, resume their attack. Why ? a .they cannot maintain their pace and must pause for a moment's rest or b. while running tiger beetles are unable to process the resulting rapidly changing visual information, and so quickly go blind and stop. Now let's look at option B Here the statement undermines the both statement "a" and "b" mentioned above. the beetles usually respond immediately to changes in the insect's direction -- This statement explains that beetles can process rapidly changing visual information, hence undermine statement b . pause equally frequently whether the chase is up or down an incline --This statement explains that no matter going up or down,beetles pause equally frequently.Thus taking rest is not the reason for pause and this undermines statement a . Now let's see option C. although when an insect that had been stationary begins to flee, the beetle increases its speed after its next pause. As per above line if beetle increases its speed immediately then the statement would have supported statement B mentioned above. But that's not the case, beetle needs to stop to see the position of insect,hence this undermines statement B . the beetle increases its speed after its next pause - Why beetle have to take pause to increase its speed ? Because beetle wanted to take rest hence it supports statement A . If beetle had increased its speed immediately after beetle started flying then this line would have undermine statement B also. I hope it helps

BTW loved your dp, Junior Ninja

Raman109 · Answer

Option Elimination -

A. When a prey insect is moved directly toward a beetle that has been chasing it, the beetle immediately turns  (It means it can see clearly - no visual issues)    and runs away without its usual intermittent stopping  (no need to take rest) - undermines both.

B. In pursuing a moving insect, the beetles usually respond immediately to changes in the insect's direction  (It can see properly - undermines theory 1) , and pause equally frequently whether the chase is up or down an incline  (pause equally frequently up or down the incline - undermine theory 2 as well)  It suggests there is some other reason.

C. The beetles maintain a fixed time interval between pauses  (ok. supports theory 1) , although when an insect that had been stationary begins to flee, the beetle increases its speed after its next pause  (it means it can see - undermines theory 2).  Increasing speed means it can cover more distance in the fixed time interval after which it pauses (still supports theory 1).

D. If, when a beetle pauses, it has not gained on the insect it is pursuing, the beetle generally ends its pursuit. -  no info to either support or undermine any theory.

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.

Kratosgmat · Answer

A the guy turns and runs without stopping 
beetle is neither blind (cuz he doesnt stop to see) nor tired (cuz he doesnt get tired and stop), so both hypothesis fails
B they pause equally frequently 
beetle is getting either blind (cuz he stops to see) or tired (cuz he gets tired and stop), so both hypothesis pass
C bee sees prey stationary/leaving,fixed time interval between pauses - so he stops to see
 bee sees prey leaving he increases his speed- which means he gets tired faster and must have stopped earlier(not at fixed time intervals) 
C is right because one hypothesis pass, other fail
D if when it pauses, it has not gained, ends pursuit
beetle is blind (cuz he stop to see) and tired (cuz he got tired and stop to catch breath), so both hypothesis succeed
E sometimes stop immediately
beetle stops to catch breath, they never go around because they are blinded

PReciSioN · Answer

most explanations here suggest that choice C seems to support the first explanation (beetle gets tired) rather than the second explanation (beetle is unable to process rapidly changing visual info and goes blind).

Choice C - "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."

However, if a beetle was indeed pausing due to getting tired, then shouldn't we expect the intervals between pauses to go down, (rather than remain fixed) or the frequency of pauses to go up. Also, that it can increase it's speed after a pause would suggest that it didn't pause due to being tired (if that were the case, surely the speed after a pause should be lower to speed before the pause).

So I believe that it undermine the tiredness explanation.

Although I do fail to see how this option strengthens the rapidly changing visuals explanation.

GMATNinja avigutman would really appreciate your thoughts!

Thanks!

GMATNinja · Answer

I think you're spot on to see that (C) undermines the first hypothesis rather than the second.

As you suggest, the consistency of intervals between pauses would lean against the hypothesis that the beetle is pausing simply in response to fatigue. Additionally, the fact that the beetle increases its post-pause speed specifically when a stationary prey insect has begun to flee -- not necessarily after  every  pause -- would point to that increase as a potential response to the prey's flight, rather than the general effect of recovery from fatigue. Further, if that speed increase doesn't occur until  after  the pause, it seems that the prey's flight is pinpointed  during  the pause. This is consistent with the hypothesis that the pause is connected to visual recalibration.

If, in an alternative scenario, the beetle could determine the prey's flight while still running, it would seem probable that the beetle would EITHER change its speed immediately OR perhaps pause immediately (if indeed a recovery were needed before launching into heavier pursuit), and neither of those seems to be the case here. The frequency of the pauses is consistent -- not determined by the timing of the prey's flight.

One last thing to keep in view: all we need to support/undermine a hypothesis is information that makes it more/less plausible. A correct answer here doesn't have to absolutely rule out  any  possibility of one hypothesis and give us indisputable, ironclad evidence of the other.

Honestly, I'm not sure that (C) would be able to meet that bar. But it does make the first hypothesis  less  plausible and the second  more  plausible in a way that the other choices don't, and that's all we need here.

I hope that helps!

PReciSioN · Answer

Nice explanation  GMATNinja  ! Especially the recalibration part which gives support to the visual theory!

ashutosh_73 · Answer

Hi @GMATNinja    @GMATNinjaTwo  @ReedArnoldMPREP @AjiteshArun @MartyTargetTestPrep

This one is really weird, and really messed up my head!
Couple of options were easy elimination but (B) & (C) seemed open to interpretation. I would some help in understanding them.

Theory 1:  cannot maintain their pace and must pause for a moment's rest
 Theory 2:  while running beetles quickly go blind and stop.
 
''immediately'' undermines T2, and ''without intermittent stopping'' undermines T1.
 Not my answer 
 
''responds immediately to changes'' undermines T2
pause ''equally frequently'' should support T1, as it seems to remove one directional objection, objection such as ''No no they only stop intermittently when in horizontal movement because they need to align themselves with the earth's magnetic field!!
 Should be my answer! 
 
This option seems contradictory. ''Maintains a fixed speed'' can support both T1 & T2, but ''increases speed after the next pause'' seems to weaken both T1 &T2. I am not sure. Here i literally lost my mental capacity to think about this option. Seemed as though, i am bending backwards to make this option work!!
 
IRRELEVENT
 
''stop immediately'' undermines T2, but no effect on T1
 Not my answer

KarishmaB · Answer

Discussed in detail here: https://youtu.be/3aAuN_bYUQ0

Dream009 · Answer

https://www.youtube.com/watch?v=jz5vTNtCbUI As per GMAT whiz- last set - Answer is B - why is this so confusing

Tiger beetles are such fast runners that they can capture virtually an

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