Q7 - All zebras have stripes

[ali.charania]

Why is D the right answer and C the wrong one?

Thanks!

[noah]

Why is D the right answer and C the wrong one?

Thanks!

How do you see (C) supporting the argument?

The argument that you're asked to support is this:

Stripes must be important + Stripes don't function as camouflage --> Stripes serve as signal for other zebras

A gap I see is that the stripes don't have some other purpose. Also, who says stripes are helpful in signaling? Perhaps they actually make things confusing. Let's look at the answers.

(A) is irrelevant to the conclusion. Who cares what other characteristics that group has?

(B) might actually weaken the argument - we need to support the idea that the stripes are a signal to other zebras.

(C) is tempting since it refers to visual signals, but where is the temporary change coming from? Out of scope.

(D) seems fishy, but it's about signals. Keep it.

(E) is out of scope - vocal signals?

So, we're left with (D). And this does support the argument because it shows that strips actually do help with signaling.

[dylancox_12]

Couldn't you argue A supports a conclusion regarding a signalling function? If a subspecies of zebras with well-defined stripes has exceptional size and vigor, then perhaps we could argue the level of definition of stripes is, for zebras, correlated with the size and vigor of a zebra. So these attributes (stripe definition) could provide a signal to other zebras that a certain specimen has vigor and size? I can see how D is correct though, but not sure how it's MORE correct

[noah]

Interesting question and creative interpretation.

I think the issue in your reasoning is that there's no discussion in (A) of signalling - you had to add that in. Who knows if the zebras can read these signals? (D) makes that clear.

What do you think?

[lbalocca]

What I don't understand is that neither A or D explicitly refers to signals. D gives a reason why zebras would see a moving zebra better because it has stripes, but that does not mean it serves as a signal. In order for that to be right, you have to assume that a there is some utility for zebras to notice when they move, which seems less likely than the stripes serving as a signal to potential mates.

Is it possible that A is wrong because it gives a reason why the most widespread species has the best-defined stripes, but does not give a reason for why stripes in general are a signal? In which case I suppose A's scope is too narrow.

[noah]

That's a good point - particularly about the scope. As for (D) I'd argue that noticing something is an inherent part of a signalling system.

[mic_a_chav87]

I also found this question confusing and chose A without much thought. However, after I chose it I made the classic mistake of not reading the rest of the answers too carefully.

I agree that strips indicating size and figure could be a signal mating, but is not explicitly mentioned. Whereas I also agree that a characteristic that helps other zebras notice movement is the same as a signal.

Sigh, lessons learned: look for the most explicit answer, don't rush through other answers when you think you have the winner.

[noah]

Sigh, lessons learned: look for the most explicit answer, don't rush through other answers when you think you have the winner.

BRAVO!

[schmid215]

Did anyone else think the stim was a bit ambiguous? For me, "...the species" in the second sentence referred to the sub-species and not Zebras in general. I'm not willing to defend my choice, (C), because it doesn't even make sense in the context of my interpretation, but it just really bothers me when there's something ambiguous in the stim. I suppose "These stripes..." would have been better for my interpretation, but then of course "Stripes..." would have been better for the test-writer's version. "The stripes..." seems ambiguous.

[noah]

Did anyone else think the stim was a bit ambiguous? For me, "...the species" in the second sentence referred to the sub-species and not Zebras in general. I'm not willing to defend my choice, (C), because it doesn't even make sense in the context of my interpretation, but it just really bothers me when there's something ambiguous in the stim. I suppose "These stripes..." would have been better for my interpretation, but then of course "Stripes..." would have been better for the test-writer's version. "The stripes..." seems ambiguous.

Interesting - I didn't notice that before. It is a bit vague, but "the" does indicate we're discussing something we discussed before.

As for the species, if they were referring to the sub-species, I think they'd have to say "sub-species."

However, I will say that your post reflects some very close reading, which is much more important than getting #7 on PT 14 correct. One idea is to go in with a "looser" read and dial it in when you face multiple tempting answers.

[griffin.811]

I'm with the masses on this one in choosing A. I thought the stripes could signal a healthy mate in the case of answer choice A.

I just wanted to add this thought in case it helps someone.

A signal should trigger a reaction. D links this reaction to the stripes. It also mentions explicitly that ZEBRAS react this way because of the stripes, which is a close parallel to the stimulus which says "...signal for other Zebras".

A never speaks to any reaction. We have to assume that that the stripes relay this message of size and vigor to other Zebras. Then we must assume that they use this info in some way, perhaps mating. The issue is we could just as easily assume that humans are the only ones that have made this connection between stripes and size, which is very reasonable. Imagine zebras hsave bad eysight and cant distinguish shape definition. Maybe they just see the pattern, and can regonize when its moving or staionary.

Too many assumptions with A.

[WaltGrace1983]

Could (A) also be wrong because we are talking about stripes in general in the argument but (A) breaks stripes into sub-categories, which the argument simply doesn't do?

[maryadkins]

I don't think so because the argument does, in the second half of the first sentence, say that the most widespread sub-species has the best-defined stripes (it's a single sub-species with really great stripes). (A) is talking about that same sub-species.

[Mab6q]

I'm going to provide my reasons for why A and C are clearly wrong.

A. tells us that the subspecies with best defined stripes is characterized by exceptional size and vigor. I kind of think of this answer choice as a correlation. We don't know that the stripes cause the size and vigor of zebras, so we cant assume that when other zebras look at stripes, it signals size and strength. Is this relationship between size/vigor and stripes the same for all other zebras. We don't know, which shows why A is such a weak choice.

C. is even weaker. C starts off good, but the last part is a train reck. A visual signal transmitted among members of a species can consist of a temporary change of color perceptible to other members of the species.

We know that the zebra stripes do not temporary change, they are permanent. Throw in the fact that they are supposed to change in color and it's completely off.

D is not perfect, certainly, but it's better than A and C. It talks about stripes and reacting (reacting to signals), which is a good start. They are more alert and respond faster to stripes. If that's the case, than it supports, not establishes, the conclusion that the stripes serve some function.

[keane.xavier]

I think there is a much clearer answer as to why (A) is wrong.

Here's my two cents, for what it's worth:

A. We know from the stimulus that the most widespread subspecies of zebras has the best-defined stripes. Additionally, this answer choice provides us with the information that this subspecies also exceptionally large. Thus, this answer choice suggests that this subspecies has larger and better-defined stripes than do other zebras. However, this tells us little about what those larger and better-defined stripes do or what their function may be. Particularly, this information doesn't rule out the possibility that these larger and better-defined stripes could instead serve a camouflage function of some sort in certain instances--say, in tall grass.

Truly, this answer choice provides information that doesn't impact the argument in any way. In some ways, we are where we initially started after reading this answer choice: they have bigger stripes; big deal--what do their bigger stripes do?

[hayleychen12]

I have a rather strange question: in the first sentence, subspecies was mentioned, and together with the second sentence, it kind of made me feel that the argument core is about the subspecies rather than zebras as a whole.
So my original thought was to find an statement that support why those subspecies with the best-defined stripes is more widespread.

Feel so overwhelmed by this one.

[ohthatpatrick]

This is really just about paying attention to the question stem. There are two conclusions: one is in the 2nd sentence (signaled by "therefore). The other one is the 2nd half of the last sentence (signaled by the "Since in the first half of the sentence).

They're asking us to strengthen the claim that "the stripes serve as some sort of signal for other zebras."

We would either strengthen by RULING OUT AN ALTERNATIVE EXPLANATION for the stripes or by INCREASING THE PLAUSIBILITY of the "signaling hypothesis".

[JosephV]

I'll chime in, too, in particular why (A) is wrong.

(A) says that a sub-species has the best-defined stripes. This refers to the entire sub-species as a whole.

The stimulus conclusion is that, speaking of all zebras (i.e. all sub-species), stripes signal something from one zebra to the other.

Since (A) is addressing one specific sub-species, and (I think reasonably) assuming that there is no cross-copulation between sub-species, what is (A)'s significance for the conclusion?

If a wide-striped zebra showed itself to an animal from a different sub-species, they could not mate, so what would be the point, i.e. what signalling are we talking about? One horse saying to another "I'm bigger, better, badder?"

If, on the other hand, a zebra of that wide-striped sub-species showed itself to another zebra of the same sub-species, being wide-striped would not make any difference because all zebras of that sub-species are wide-striped. Meaning, a mare would not be inclined to choose one stallion over another because both stallions are of exceptional size and vigour. (Truthfully, we don't know about any variation within the sub-species in the size of the stripes, so my conclusion is not iron-clad, but it still tilts the argument in favour of some other answer choice, not (A)).