Critical Reasoning

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.

Doubt: The official answer in the OG12 is not clear. I got the answer but with a different explanation.
B--> since beetle is chasing a swerving insect which alters its course visually things are fine for the beetle.
Since the pauses are becoming frequent after the chase it means beettle is becoming tired.

As per the OG explanation for option B only second hypothesis is getting strengthened which should not be the case. You need one hypothesis to be strengthened while second hypothesis to be weakened .

OA B

Option B strengthens the second hypothesis and undermines the other.

Answer Choice B would actually both strengthen one hypothesis and weaken the other.

If the first hypothesis is correct and the beetle essentially runs out of breath then the beetle will need to stop more as it runs faster or for longer distances. If the beetle is stopping for visual reasons it will also need to stop more frequently as it runs faster, so for example, Answer choice E would not help because both hypothesis are supported by the rapid running.

By contrast, answer choice B would only support the vision reason for stopping. If the insect is swerving that would cause the visual information to change even more rapidly and the beetle would need to pause more frequently as compared to a straight line.

Now the question that you have and the point that is not emphasized in the OG explanation is that this weakens the fitness or endurance hypothesis because there is no reason to stop to catch its breath more frequently simply because the prey is swerving. If the speed is the same and so forth just the swerving does not seem to be a reason to run out of breath more often.

Thanks David

well between B and C it is.

in C both the options are getting strengthened hence POE.

B remains where the second part of the sentence just gives a hint that the stopping is because of visual changes and not because of the pace.

Amit2k9 -

I agree with you that C is certainly tough to eliminate, yet I think maybe both options are weakened in C.

If the beetle pauses just as often downhill as it does uphill then it seems like it should not be caused by being out of breath - surely uphill is tougher on that account.

And as to vision, well if it responds immediately to any changes it seems like it is not a matter of information overload.

That is my take on C, anyway.

By the way, there are lots of questions out there claiming to be a top-level question. This one to me feels like 90th percentile (700-level) for sure. It makes you think and it has tough answer choices.

David@VeritasPrep wrote:Amit2k9 -

I agree with you that C is certainly tough to eliminate, yet I think maybe both options are weakened in C.

If the beetle pauses just as often downhill as it does uphill then it seems like it should not be caused by being out of breath - surely uphill is tougher on that account.

And as to vision, well if it responds immediately to any changes it seems like it is not a matter of information overload.

That is my take on C, anyway.

By the way, there are lots of questions out there claiming to be a top-level question. This one to me feels like 90th percentile (700-level) for sure. It makes you think and it has tough answer choices.

Hi Dave,
Thanks for the reply. Please help me in understanding option 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."
I believe first part sentence weakens the claim - "...capturing visually etc.." because a bettle changes the direction as the insect changes the direction.
And second sentence strengthens the claim that it rests during the chase.

My Q is the reason C is wrong because it uses the word usually or some other reason.
I mean it looks like close to B, which I understand is correct, but what's the diff

Please explain.
Thank you!

M09 -

No. no. no! We have to address this statement you made:

"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."
I believe first part sentence weakens the claim - "...capturing visually etc.." because a beetle changes the direction as the insect changes the direction.
And second sentence strengthens the claim that it rests during the chase.

We are not trying to strengthen the "claim" that it rests during the chase. This is what it says in the stimulus "However, when running toward an insect, a tiger beetle will intermittently stop and then, a moment later, resume its attack." This is not a claim - but rather a premise. The premise is a fact that cannot be contradicted or doubted but must be accepted as true.

What we are trying to do is to explain WHY the beetle stops. Is it 1) because the beetle is winded and has to rest to keep running or 2) because the beetle has too much visual information.

Now the question stem here is very clever. It does not tell us which claim to strengthen and which to weaken. The reason that B works is it strengthens the visual information as the cause and weakens the winded and needs to rest as a cause. In B we have the beetle pausing as the thing it chases swerves. So that is visual overload since swerving should not be a matter of getting winded.

C does not strengthen either of the two causes. It certainly weakens the cause 1) that the beetle stops because it is winded. The reason is that (as we all know) it is more tiring to run uphill rather than down. If the beetle were getting winded then it would stop more often as it goes uphill. But here we see that it stops equally up and down hill.

Now what about the visual information? Well, if the beetle responds immediately to the changes in direction then this means it can process the visual info. So this probably weakens the claim that visual overload is the problem. This is not as big of a weakening, but it is not out answer.

In response to your question, the word "usually" has really no impact here.