Q14 - Marine biologists had hypothesized that lobsters

[u2manish]

Dear Brian/Noah/Matthew,

I am having hard time to see the relevance of the answer(E). Can someone please walk us through. Can this be diagrammed?

I could try it myself but you will have to take it forward.
H= hungry
E= eat each other

P :H---> E
C: H----not E

How is the answer: "H"


Thanks,
M

[timmydoeslsat]

I am not Brian, Noah, or Matt (but aspire to be!)...but I will attempt to help before they come here to help.

This is necessary assumption question. In the vast majority of necessary assumption questions, the technique to use is not formal diagramming the argument. It is important to know when to use that tool and when to realize that it is a time waster.

The test writers, when it comes to necessary assumption questions, may require formal diagramming, but it would be with arguments that, on their faces, have so much logical structure it almost jumps off of the page.

In this case, we are told that marine biologists made a hypothesis. They believed that lobsters kept together in traps would eat one another in response to hunger.

The stimulus goes on to tell us that instances of lobster traps being shared without the lobsters eating one another went on for weeks, even two months without eating one another.

The conclusion of this argument is that the marine biologists' hypothesis is clearly wrong.

So the full conclusion is that lobsters kept together in traps eat each other in response to hunger is wrong.

Is there a gap here?

Well we know that the lobsters were not eating one another for all of those weeks in that instance. There was one case for 2 months.

Necessary assumption questions should be done with the negation technique on the tempting answer choices.

When you look at (E):

Any food that the eight lobsters in the trap might have obtained was not enough to ward off hunger.

Negate that:

Any food that the eight lobsters in the trap might have obtained WAS enough to ward off hunger.

When you negate that answer choice and have it say that the lobsters might have obtained food that was enough to keep away hunger. This would destroy the conclusion of the counter to the marine biologists. We could not state that it is clearly wrong that lobsters do not eat one another in response to hunger. This is because we are no longer given that possibility. Hunger was never in the running if this assumption is negated. This means that this is, in fact, something that is necessary for the argument to be valid.

[ManhattanPrepLSAT1]

Great explanation timmydoeslsat!

And while I'm guilty of this myself many times in the past, let me try to be very precise in how the Negation Test works. It's not that the negation of the correct answer will destroy the conclusion, but that it makes it so the conclusion does not follow from the evidence offered. So after negating answer choice (E), the conclusion that lobsters do not eat one another in response to hunger may still be true, but we would not be able to use the evidence provided to support such a conclusion. An assumption of this argument is that the lobsters were in fact hungry. Without that assumption the example of the lobsters would be irrelevant to a claim about what happens to lobsters in response to hunger. Answer choice (E) simply provides this assumption.

Let's take a look at the incorrect answer choices:

(A) undermines the argument that lobsters will not each other in response to hunger.
(B) is irrelevant. Two months is more than enough time to allow a lobster to become hungry, and if it wasn't, that would again simply undermine the argument.
(C) is irrelevant. The frequency with which lobsters are caught in large groups plays no role in what happens once they are.
(D) is tempting in that it suggests the behavior is common at least on other marine species, but while it helps, it is not a Necessary Assumption of the argument.

Thanks again timmydoeslsat, nice work!

[u2manish]

cheers Timmy and Matthew for clearing it up for us...!

[Jasonzhang]

I was wondering whether the negation of answer (E) would be "SOME food that...WAS enough to ward off hunger."

Will this negation destroy the argument?

Concerning answer (B), if the longest known period is three months,
will it be possible that the lobsters become hungry only after two months? If it is possible, then we would not know what would happen after two months. So, I chose B because I thought the two months would not be long enough to support the conclusion.

[db_8400]

Can someone please explain E without the negation process. I cant wrap my head around this answer!!! It's literally killing me, I'm reading the Manhattan Logic Reasoning book and it says this " the answer eliminates the possibility that the lobsters were not hungry". If this eliminates that process then how is this the assumption? B/c he/she is assuming that the lobster is hungry

[olaizola.mariana]

I think Jasonzhang's point about answer choice (B) is a valid one. What if lobsters are one of those species that need to eat every 10 weeks or so? Wouldn't the assumption that 2 months without food is enough to make lobsters hungry be required as well? Indeed, it serves the same purpose as (E).

Could anyone help shed some light on this?

[rinagoldfield]

Thanks for the conversation. A couple of points to follow up on:

We can rephrase (E) as “the lobsters were hungry.” (Much simpler, right?) After all, what they had wasn’t enough to keep hunger away.

If the lobsters were hungry, then they ARE a good counterexample to the marine biologists’ hypothesis. If they were not, then they ARE NOT a good counterexample. Hence, (E) describes an assumption.

Regarding (B), the marine biologists’ hypothesis doesn’t address time. It doesn’t matter whether the lobsters get hungry in a day, an hour, a month, or a year. What matters is whether they eat each other when hungry. For length of time to affect the argument, we’d have to bring in another assumption, like lobsters can’t become hungry in two months.