#22- The folktale that claims that a rattlesnake’s age can

[lawschoolforme]

Lucas,

Thanks so much for your explanation - it was really clear!

Sincerely,
lawschoolforme

[actionjackson]

I unfortunately fell victim to this question. For the answer choices I was torn between A and E and in my time spent between taking this prep test and reviewing the questions, I was haunted by this question and its answer choices. I had a general inclination during that downtime as to why answer choice A was incorrect and E correct but I just wanted to verify that my reasoning is sound. Initially upon looking at A I had said to myself, "Well yea, if these snakes don't molt 1x per year we can't figure out how old they are based on rattlers alone (kind of similar to how one can figure out the age of a tree based on the rings of its trunk)". But as this question continued to loom on me (after taking the test) I said to myself, "I don't even know how one could determine a rattlesnake's age on the basis of their rattler sections alone." What if the people who wanted to figure out a rattlesnake's age based on sections used something like radiocarbon dating? Then the snakes molting once per year doesn't mean much and doesn't have to be true in order for the argument to stand. Whereas E accounts for a variable that very well could imperil the reliability of the measurement method central to the argument?

[Kristina Moen]

Hi actionjackson,

The stimulus tells us that the folktale is about determining a rattlesnake's age by the numbers of sections in the rattle. So we are not talking about carbon-testing or any other methods. The conclusion is not that this is the ONLY way to tell the rattlesnake's age, so any answer choice about other methods would be wrong. The argument does not assume that there are not other methods besides counting the numbers of sections. The author is concluding that, barring brittleness, counting the number of sections is a reliable way to tell age. Answer choice (A) is incorrect because the author never tells us that we have a 1 to 1 relationship: 3 sections = 3 years, for example. Even if rattlesnakes did NOT molt once per year (Assumption Negation Technique!), the conclusion could still hold.

However, answer choice (E) is a requirement. If anything other than AGE affects the number of sections, then we cannot reliable tell age based on the number of sections. The test makers could have chosen anything that was unrelated to age - food scarcity, chemicals in the water, fear of predators, you can get creative!

[LSATer]

Hi,

Can you please explain what you mean by "an assumption answer choice is always a necessary condition?"

Thank you,

LSATer

Hello, LSFM,

You've got it half right, with your analysis of A. You do in fact need a high level of commitment, as you say, for a correct Assumption answer choice. An Assumption answer choice is always a necessary condition. The reasoning being that the correct answer choice must be assumed in order for the argument not to fall to pieces.

For this specific question, A is not absolutely mandatory for the argument to still proceed. Not specifically A, anyway. The argument would proceed properly if rattlesnakes molted, for instance, every month. Or twice a year. The important thing to the argument is that they molt at regular periods. It doesn't matter so much exactly how long the period is, as long as it's the same every time.

Hope that helps,
Lucas Moreau
PowerScore

[Dave Killoran]

Hi LSATer,

Lucas' post is from 2013, so he won't likely drop in to answer this, so I'll jump instead. What he is referring to there is the abstract structure of how assumptions work (especially in relation to Justify questions). As we explain in the course and in the LSAT Logical Reasoning Bible (see pages 298 and 345 of the 2017 edition), an assumption is a statement that is necessary for the conclusion to be true: "Because an assumption is an integral component of the author’s argument, a piece that must be true in order for the conclusion to be true, assumptions are necessary for the conclusion" (italics are from the original text). So, his reference is to the big picture of how things work in argumentation as a whole, and does not imply that the actual content of the answer choice is part of a specific conditional setup within the problem itself. Does that make sense?

Please let me know if that helps. Thanks!

[LSATer]

Okay I got it! That makes sense. I referred back to the books and I understand. I was thinking it was part of a conditional setup within the problem.

Thank you!

[LSAT2018]

Hi,

That is an assumption question, because it asks for the assumption that is required by the argument.

Had it been a Justify question, (A) would have been a winner.

I hope that's helpful!

~Steve

I would really appreciate more explanation on this. How can answer (A) be a Justify the Conclusion question as the sufficient assumption? And how does the answer differ from the necessary assumption?
I thought of the information in the stimulus as Molting → Form Sections → Reliably Determine Age and make sure age could be reliably determined as the assumption.

[Adam Tyson]

Good question, LSAT2018! The difference between an Assumption (aka Necessary Assumption) answer and a Justify the Conclusion (aka Sufficient Assumption) answer is that the Assumption answer is something that the author MUST believe in order to make his argument, while the Justify answer is one that he may or may not HAVE to believe, but if it was true it would prove his point.

In this question, in order for us to use molting to determine age, we have to assume that molting happens at some regular intervals that we can count. If the frequency of molting varied based on things like weather, food or water supply, the general health of the snake, etc., then we couldn't reliably count on the number of new sections as indicating an exact passage of time. One snake might have a low food supply and molt once in a year, while another got plenty of food and molted three times that same year. How would the number of molts/rattle sections correlate to age? It wouldn't!

Answer A, if it were true, would prove the conclusion, because it would mean that the number of sections would equal the number of years, so it is a great Justify answer. However, our author need not assume that snakes molt exactly once a year, because it would also be okay if they molted twice a year, or once a month, or every 247 days, etc. Answer A gives us ONE way to prove the conclusion, but it isn't the only way, so our author doesn't have to assume it!

Assumptions must be believed by the author, while Justify answers don't have to be true but would, if true, prove the conclusion. Think of them as the having the same difference as between a Must Be True question and a Strengthen question, and that might make it clearer.

[akanshalsat]

For this question, we need to find an answer without which, the conclusion cannot be drawn the way that it has been. So their conclusion is that the ONLY reason that the rattlesnake age folktale doesnt work is bc of the brittleness of the tail. Therefore, they are assuming that there are no other reasons for the failure of the folktale - so the correct answer must discard any other reasons for why the folktale could be said to be false.

Is it true, then, that E is correct b/c IF the rattlesnakes DID NOT molt as often when food was scarce as they do when food is plentiful (in that for example, less food out there meant more moltings and more food out there meant less molting) then that would be ANOTHER reason for why the folktale is false bc then age couldn't accurately be determined? and the conclusion is clear that there is only 1 reason its false?

I'm a little confused as to why the rest of the choices arent true

[Adam Tyson]

That's an excellent analysis, akanshalsat! Yes, the author assumes that the brittleness is the only reason why we cannot use the number of rattle sections as a reliable method of determining the age of a rattlesnake, so if we find some other reason that they are not reliable for that purpose, that would hurt the argument. The correct answer will likely eliminate some, or all, other possible problems with reliability.

As to the four wrong answers, it's not that they are not true, but that they don't have to be true. An assumption answer must be true, at least in the mind of the author, and that's why we can test the answers with the Assumption Negation Technique. If we negate a wrong answer, it will not destroy the argument, but the right answer, when negated, does exactly that. So, for example, answer A (perhaps the most attractive of the incorrect answers) gets negated as "rattlesnakes do not molt exactly once a year." That doesn't ruin the argument because they could still do so at fixed intervals that we could use to determine their age, like once every 6 months. But when we negate answer E, we get "rattlesnakes do not molt as often when food is scarce as they do when food is plentiful," and that ruins the argument because age is no longer the only factor in molting and we could not be sure of a snake's age by counting the number of sections in the rattle. We would know how many times they molted, but not how long it took for them to do that.

Try that negation approach on the other answers and you should find that none of them destroy the argument when negated. That's proof that they are wrong answers! That technique always works, if you do it correctly.

Good luck!