#6 - The waters surrounding Shooter’s Island have long been

[Administrator]

Please post your questions below!

[sylvia11]

I thought (D) is correct and (C) is wrong for the following reasons. In (C), it says that "waterbirds use still waters as nurseries for juveniles whenever possible". Because the island in question is "exceptionally still", we don't know whether other islands are rough or still, just that the Island has probably the most still water. I thought this gives causal reason on why the young birds are concentration around the Island but I thought it would raise a question on why there aren't as many young birds in other islands if having still water is enough.

For (D), I thought it gives the classic strengthening of "no cause, no effect." Because other islands are much rougher than the Shooter Island, it strengthens by explaining why the situation is the way it is.

[Adam Tyson]

The thing to focus on here, sylvia, is the causal aspect of the argument. What is causing a higher concentration of juvenile birds at Shooter's? The author thinks "it's a nursery" is the cause of that disproportionate number of juveniles. Answer D tells us that there is something different about the other islands, but tells us nothing about whether "nursery" is the cause. In fact, with a little imagination answer D actually weakens the argument. Maybe it's not a nursery, but just that juvenile birds can't handle the conditions in rough waters?

Think of it as a causal chain: abandoned boats cause still waters, which cause birds to use it as a nursery, which causes a higher proportion of juveniles. The stimulus already gave us the first link in the chain, and it also gave us the final effect. The author proposed the middle link in the chain to connect it all together, and answer C confirms that link. D doesn't connect to the causal chain in any way, but leaves us still wondering whether still waters lead to use as a nursery.

[Oneblackcoffee]

Hi - is A/C (C) not circular reasoning because the question stem says, “which one of the following, if true...”? Said differently, if someone were to say, “The still waters are probably nurseries because water birds typically use still waters as nurseries,” then we could, without knowing the truth of the latter part of that sentence, say it’s circular reasoning? I got caught up on this while taking the test and ended up choosing (B) because I thought (C) was circular. Thanks in advance.

[James Finch]

Hi One Black Coffee,

Circular reasoning involves inferring as a conclusion the premise upon which it's ostensibly based. The clearest example tend to be comparisons, such as "Karen is the best at basketball because she plays it better than anyone else." The conclusion will simply restate what the premise is saying.

Here, (C) doesn't actually do that; you may have made this assumption, as it does seem inherent to the argument in the stimulus, but it's not actually stated. No reason is given as to why still waters would be associated with waterbird nurseries, although we could clearly guess. (C) makes that guess/assumption explicit, and in so doing bolsters the argument being made.

Hope this helps!

[sicm91]

Hi! I am having trouble seeing how B does not support the conclusion since it eliminates an alternative explanation for the increased presence of juvenile waterbirds. Could someone please explain this to me? Thanks!

[Adam Tyson]

The ornithologist found that juveniles constitute a higher proportion of birds at Shooter's than elsewhere, sicm91, and this answer confirms that her finding is consistent over time, but it doesn't tell us anything about WHY that's the case. Is it because it's a nursery? Because juveniles near other islands die at a higher rate, perhaps due to predators or other environmental factors? Is it because juveniles like the wrecked boats and so gravitate to Shooter's, while the older birds find the boats annoying so they tend to leave? Answer C gives us a much clearer, stronger reason for accepting the conclusion, while Answer B should still leave us asking ourselves "why?"

If the numbers DID fluctuate dramatically throughout the year, we would still have to ask ourselves a few more questions. Does Shooter's maintain a higher proportion of juveniles even while the actual numbers fluctuate? Why do they fluctuate - is it because of birds hatching more at one time of year than another, or for some other reason? And what, if anything, would the fluctuation tell us about whether Shooter's is a nursery? I'd still be scratching my head trying to figure out what that would mean for us!

[silver2731]

I have chosen D instead of C for the answer. Below is my reasoning and I hope I could get review on it so I can reflect it on my future exams.

Answer C was not enough to strengthen the original argument's reasoning. The reason why is it is a mere repetition of the conclusion.

Conclusion: the still waters around Shooter's Island serve as a nursery for the juveniles.

Answer C: Waterbirds use still waters as nurseries for juveniles whenever possible

The only difference is "whenever possible." Timing of using still waters as nurseries does not add anything in my opinion. Especially when there are still waters in other island too.

The reason I thought D was strengthening the argument is per my intrepretation of reasoning structure in the original argument below:

Premise: Shooter island has more juvenile waterbirds than other islands.
Conclusion: Shooter Island has still waters around it which serves as the nursery for the juveniles.

I believe to make the above two step logically valid, we need an assumption/inference that shooter island has still waters and other islands don't or has less that would suffice to make the difference/contrast.

I thought other islands having rougher water gives this contrast and surely strengthening the argument.

[Beth Hayden]

Hi Silver,

I know it looks like it at first glance, but answer choice (C) is actual not repetitive.

The stimulus tells us that the water around Shooter's Island is very still, and that there are a lot of juvenile waterbirds there. The author then uses those facts to conclude that it must be the case that this area is a nursery for the juveniles. The language would seem to indicate that the waterbirds seek out the waters around Shooter's Island specifically for the purpose of raising their young. But that still leaves a question--why there? Why would the waterbirds choose that particular area?

Answer choice (C) provides us with a possible answer to that question. If waterbirds always try to find still waters when they are looking for a place to use as a nursery, and we already know that the water around Shooter's Island is still water, the conclusion makes a lot more sense.

Now remember, this is a strengthen question, not a justify the conclusion. The answer choice doesn't have to prove the conclusion 100%, it just has to make it more likely to be true. So it's not a problem that answer choice (C) doesn't explain why they chose Shooter's Island and not another island with still water. Maybe this island was in a prime location? Maybe it was just random? Maybe it had the calmest water of anywhere else? It doesn't matter! We don't have to explain why they didn't choose any of the other islands, just provide a reason why it makes sense that they chose this one. Answer choice (C) does that by saying that Shooter's Island had certain characteristics that waterbirds seek out when looking for a nursery for their young.

Now answer choice (D) might explain why Shooter's Island is better than the other islands, but that's not an issue here! The conclusion doesn't say that Shooter's Island is the "best" place to put a nursery, just that the waterbirds chose it for that purpose.

Remember, without answer choice (C), based purely on the premises, we have no reason to believe that still waters are best for nurseries. That logically makes sense, but I know nothing about waterbirds and what they are looking for when it comes to raising their young! Answer choice (D) alone, without (C), doesn't necessarily help the argument. Ok, the water on the other islands is rougher, so what? Your reasoning would make total sense IF there was a premise that said what (C) does (that still water is best for nurseries), but there isn't. Without that fact we have no way of knowing whether answer choice (D) is helpful, hurtful, or has no effect on the argument.

I hope that helps!
Beth