#12 - Must Be True

[reop6780]

I assumed Q12 to be "must be" question as most of other questions.

The correct answer is A but I spent time choosing between B and E, both of which has something to do with spade foot toad tadpoles' cannibalism.

While was considering B and E, I realized neither of them are fully supported by the passage but did not consider answer A AT ALL.

I guess the line 41, " they nip at other tadpoles.." support answer A..?

Still the way answer A states "visual cues" out of nowhere was indeed confusing of rather made me exclude that answer quickly when it was the only correct answer.

Is this kind of phrasing common in RC?

Also, could you convince me of the answer A in regards with why it must be correct?

Thank you

[Nikki Siclunov]

Hey reop6780,

Thanks for your question. What you're looking at is a common psychometric trick: test-makers know that students often disregard any answer choice that appears to introduce new information when answering Must Be True questions. This is precisely why you eliminated answer choice (A). However, read closely: it says that the mechanism by which tadpoles recognize their kin is not dependent solely on the use of visual cues. Despite the seeming introduction of a new term ("visual cues"), this statement can easily be proven by reference to lines 39-43. Since “nipping” is a form of tactile communication, it is reasonable to infer that tadpoles do not rely solely on visual cues (i.e. they also rely on tactile cues).

This is an easy trap to fall into, but it's also easy to dig yourself out of it. While truly new information is, by definition, impossible to prove, keywords are not a reliable clue. Read carefully and closely, and you won't make the same mistake again

Good luck!

[ataraxia10]

Hello, I understand that nipping supports answer choice A, but wouldn't the fact that "all tadpoles of that species begin life as omnivores...but that occasionally one tadpole eats another or eats a freshwater shrimp. This event can trigger changes...causing the tadpole to become larger and exclusively carnivorous" support answer choice E by the same logic? Or am I confusing the necessary condition with a sufficient condition here?

[Jay Donnell]

Hi ataraxia!

I think one point that had to be stressed about this question is to keep in mind that it is a Most Strongly Supported question, which carries with is some majorly useful predictions about answer choice characteristics. In MSS questions, just like in MBT questions, we have to be very cautious about answer choices that contain very strong logical force. Very, (very!) often the correct response is of a low logical force, as that level of strength in a statement would be easier to support/prove.

I think of these questions with the analogy of support like a budget, and how in looking to support(afford) an answer, we should be drawn to the weaker(cheaper) answers for a higher likelihood of being able to do so.

Though answer choice A contains several words that taken independently contain high levels of logical force, paired together as they are actually presents a very weak statement. To say that a given situation is 'not dependent solely' on a given factor, it just means that some other factor can play a role.

The reason I bring this up is that D brings with it a rather large amount of logical force with its phrasing of 'could not have', which is synonymous to calling something impossible. We know that tadpoles are born with every member of the species being omnivorous but that sometimes through cannibalism certain individuals can develop into purely carnivorous diets. The kin recognition we're asked about comes into play with the carnivorous (and cannibalistic!) tadpoles who refrain from eating their relatives.

This means that kin recognition developed in an animal population that contained at least some pure carnivores, but that doesn't nearly give us sufficient proof that similar recognition 'could not have' developed in groups of animals with different dietary needs/wants.


I hope that helps!

[ataraxia10]

Hi Jay, thank you for the thorough explanation and useful tip about MSS. That makes a lot of sense.

[PresidentLSAT]

Hi Powerscore,

I didn't know the meaning of "nipping" so I ruled out A.

I chose B but my reasoning for supporting the answer choice was that the process of discrimination comes after they've become cannibals, or at least we are provided with that information after the passage informs us of their evolution to becoming exclusively carnivorous. Specifically, line 36 " Yet the cannibals" referred to the tadpoles as exclusively animal-eating species.

From this, it seemed it was reasonable to infer that the mechanism doesn't apply to noncannibalistic tadpoles.

I also think I may be committing a local error here by assuming a particular trait doesn't apply to a group of species because it hasn't been proven.

Any advice on my approach to choosing B will be appreciated.

[Robert Carroll]

PresidentLSAT,

There is no way to know whether non-cannibal tadpoles have the mechanism. The statement you cite merely says that the cannibals have it. Nothing about that entails non-cannibals don't. We're lacking any word like "only" or something else that would say it's an exclusive ability of cannibals.

Robert Carroll