#16 - The authors of a recent article examined warnings of

[blade21cn]

I thought this is a tough question. Can any expert explain why (A) is correct? The opposing viewpoint comes from these article authors saying that no evidence exists to support the idea that the rate of extinction of animal species is now accelerating. The conclusion basically says these authors are wrong. When the borrowed language was put back, we get: it is not true that no evidence exists to support the idea that the rate of extinction of animal species is now accelerating. In other words, there is some evidence that the rate of extinction of animal species is now accelerating. I thought the language used in the conclusion ("some") is weak and it could be bolstered by just one counter-example, which we get from the premise about the extinction of 40 species and subspecies of North American fishes.

(A) seems to hinge on whether the extinct fish species are representative of animal species in general. But wouldn't the notion that at least some fish species manifest accelerated extinction be sufficient to reject the opposing view, which contains strong language - "no evidence (whatsoever)," regardless whether the example is representative or not?

Also, the new term "pattern of extinction" in (A) is ambiguous. Though it could mean "rate of extinction," it could also be interpreted as their die-off pattern, or how they became extinct, e.g., illegal poaching, water contamination, pollution, deforestation that deprived the animals of their favorable habitats. Actually, this is the exact reason I eliminated (A). I thought the "pattern of extinction" was out of scope, since the argument only cares about the fact that they are extinct, not how they became extinct.

Instead, I chose (B), as I thought "rate of extinction" is also ambiguous. It could mean the number of species that are extinct over a set period of time, or the speed they become extinct. For example, an extinct species with a previous population of 100 million would be seen as faster (more accelerated) extinction than another extinct species with a previous population of 100. Thanks!

[Paul Marsh]

Hi blade21cn! You've stated the conclusion of the stimulus's argument nicely: "there is some evidence that the rate of extinction of animal species is now accelerating".

As always for (the ever rare) Evaluate questions, we want to identify the logical Gap between conclusion and premises. The only real premise for this conclusion is the last sentence: "Consider only the data on fishes...". To find the Gap, we ask whether our conclusion follows 100% from our premise. Does the data about the rate of fish extinction increasing necessarily mean there is some evidence that the rate of animal species extinction is now accelerating? It does not. The Gap here is that the argument jumps from its premise of "fish" to its conclusion of "animal species". In doing so, it ignores a distinct possibility: the rate of extinction for all non-fish animals has drastically decreased, and so the evidence in fact points to the rate of extinction for all animal species decelerating!

It's like the following argument: "My Acting 201 grade this semester is higher than my Acting 101 grade was last semester. Therefore, Mom and Dad, we have evidence that my overall grades are going up!" In order to really validate how accurate your conclusion is, your parents are probably going to want to know whether your Acting grade is representative of the rest of your report card! It's the same thing in #16.

We can test this with the Variance Test: if fish are not representative of all animals when it comes to rate of extinction, then the conclusion about overall animal species extinction rates is severely weakened. If fish are representative, then the conclusion is seriously strengthened. This is the sign of a good Evaluate answer choice.

(B), on the other hand, doesn't address that Gap at all. It's also wrong in its own right - in context, I think that "rate of extinction" in this passage pretty clearly refers to the number of species that are going extinct, which makes (B) fairly irrelevant to evaluating the argument.

Hope that helps!

[lmrlmr]

Hi,

I was confused by answer choice A's use of "unrepresentative" which in turn led me to choose answer choice B. I thought that if it had used "representative" instead it would have been more attractive. Can you help me understand why the test writers added the "un" and how this still makes the answer choice correct?

Thank you!

[atierney]

In terms of why they added the "un" to the word representative for this evaluate the argument, I think the main reason is that the presumption in the argument is in favor of representation, especially as used by the argument. In other words, the argument jumps the whole of animal kingdom (animal species generally), and uses a part of that kingdom (the fish) to conclude that a statement made about animal species as a whole is wrong. Now, here, obviously, the argument is assuming that there is no "whole to part" error in division here. What is true of the fish species must be representative of the entire set of animal species at large; otherwise, the particular example does not prove the authors wrong, in so far, as their claims speak to the rate of extinction to the animal species overall.

In evaluating this argument, then, as stated above, we can use the Variance Test with the sufficient condition of "not being representative," which if satisfied, will allow us to necessarily conclude that the evidence used to support prove the authors wrong is not in fact able to do so, thus crippling the conclusion that the authors were in fact wrong.

Let me know if you have further questions on this.