#25 - The interstitial nucleus, a subregion of the brain's

[Sophia123]

Hi!

I was quite confused on this question and ended up selecting answer choices (a) and (b) because I found it to be pretty convincing. Looking back, I can see why answer choice (e) is correct since it severs the link between the hypothalamus and disease Y (and thus disease X). However, I thought answer choice (a) showed the cause without the effect, which would thus weaken the argument. My thought process was that if no female cats have contracted disease X, and in the stimulus it says that the male cats that contracted the disease had a hypothalamus as large as those in female cats, that would show the cause (large hypothalamus) with no effect (disease X). I was also pretty convinced by answer choice (b) because it seems to give an alternative cause by bringing in disease Z. For example, maybe some unknown factor causes disease Z, which in turn leads to disease X. As a result, maybe the hypothalamus isn't involved in this at all and it is just this other unknown factor that is causing it.

Am I just assuming too much in my analysis of (a) and (b)?

Thank you in advance!
-Sophia

[Luke Haqq]

Hi Sophia!

Happy to offer some thoughts on why (E) is preferable to (A) and (B) in this question.

First off, it's great that you're using PowerScore's suggested categories to think about how to weaken a causal relationship (e.g., cause without effect, alternative cause, etc.). Knowing those definitely will come in handy, as with this question.

With regards to answer (A)--on the one hand, you're right in one sense that it'd show the cause (large hypothalamus) without the effect (disease X). On the other, it's not the exact cause in the argument. Namely, the argument is about whether the size "determines whether or not male cats can contract disease X." Since (A) addresses females, it doesn't get directly to the question's argument, so it's not the best contender for a weaken question.

Regarding (B), the possibility that there is an unknown cause of Z similarly doesn't get at the causal argument in the stimulus. The causal argument is about whether larger interstitial nucleus size determines whether male cats can contract disease X. If those contracting disease X also get disease Z, you're right that this might be evidence of an alternate cause giving rise to both X and Z. But even if such an alternate cause existed, it wouldn't get to the argument that there's a brain-size/disease X relationship. For example, that alternative cause (which causes X and Z) might itself be responsible for increased interstitial nucleus size--but even if that were the case, it wouldn't weaken the claim that "the size of the interstitial nucleus determines "whether or not male cats can contract disease X"--it would leave argument untouched.

Hope that helps!

[LSAT2018]

Just to clarify for answer (B), can it be incorrect because it hasn't provided sufficient information that would weaken the causal argument? Because it says 'the cause of which is unknown' there is no indication whether disease Z would have the same cause as disease X, and so citing this correlation between disease X and disease Z is not entirely effective because there we cannot confirm whether this refers to the alternate cause.

So had the answer said something like XXX causes disease Z and X in most male cats, it would have been an acceptable answer?

[Adam Tyson]

That's a good analysis of answer B! "We don't know the cause of Z" isn't the same as saying there's a different cause for X. Well done!

[silent7706]

I found this one interesting. Answer (B) and (D) offer alternative cause and cause without effect respectively, both can weaken the causal relationship in the argument. The correct answer (E), while addressing causality directly, requires the assumption that what's true for the whole, must be true for the division. I'm not very convinced on this one.

[Adam Tyson]

Answer B doesn't actually suggest an alternate cause for disease X, or for susceptibility to disease X, other than the enlarged interstitial nucleus. Perhaps disease Z is an additional effect of that enlargement? Perhaps disease X causes susceptibility to disease Z? Maybe it's just a coincidence with no causal connection? A true alternate cause answer has to do more than say that other things also happen - it has to suggest that the purported cause may not be the real cause. B doesn't go that far, because the enlarged interstitial nucleus could still be causing susceptibility to disease X no matter what is going on with disease Z.

Answer D isn't quite a case of cause without effect, because although the interstitial nucleus in these cats is larger than average, we don't know that it is as large as those generally found in female cats, and that seems to be the determining factor. Plus, it's not about whether an enlarged interstitial nucleus causes the disease - it's about whether an enlarged interstitial nucleus determines a cats susceptibility to the disease. So these cats may indeed have the effect - susceptibility to disease X - even though they managed not to get it. That is, they could have gotten it, but they just didn't.

Answer E kills the argument completely. If the hypothalamus is KNOWN not to be a cause of Y, and X is a type of Y, then neither the hypothalamus nor its components (including an enlarged interstitial nucleus) can be causing X.

Very attractive wrong answers on this one! We have to be very picky about what they mean!

[silent7706]

Answer B doesn't actually suggest an alternate cause for disease X, or for susceptibility to disease X, other than the enlarged interstitial nucleus. Perhaps disease Z is an additional effect of that enlargement? Perhaps disease X causes susceptibility to disease Z? Maybe it's just a coincidence with no causal connection? A true alternate cause answer has to do more than say that other things also happen - it has to suggest that the purported cause may not be the real cause. B doesn't go that far, because the enlarged interstitial nucleus could still be causing susceptibility to disease X no matter what is going on with disease Z.

Answer D isn't quite a case of cause without effect, because although the interstitial nucleus in these cats is larger than average, we don't know that it is as large as those generally found in female cats, and that seems to be the determining factor. Plus, it's not about whether an enlarged interstitial nucleus causes the disease - it's about whether an enlarged interstitial nucleus determines a cats susceptibility to the disease. So these cats may indeed have the effect - susceptibility to disease X - even though they managed not to get it. That is, they could have gotten it, but they just didn't.

Answer E kills the argument completely. If the hypothalamus is KNOWN not to be a cause of Y, and X is a type of Y, then neither the hypothalamus nor its components (including an enlarged interstitial nucleus) can be causing X.

Very attractive wrong answers on this one! We have to be very picky about what they mean!

Thank you for your explaination!

[PresidentLSAT]

Hello Powerscore,

I love love loooooove this question even though I got it wrong lol.
Can someone kindly assess my think for running through the answers?

a. I think A is irrelevant. There is a relationship been draw in the stimulus between male cats and the size of their IN. What happens among female cats even if it was a strong weakner for female cats won't effectively attack the argument made for male cats. After all, they are difference and the stimulus doesn't give us reason to assume they function the same internally.

B, I eliminated because disease Z could be an exacerbated effect of disease X. If my throat swells whenever I get a cold and if I get a fever whenever I get a cold, that doesn't mean the the presence of the swelling disappear. And if the cause of the fever is unknown, does it really serve as an alternative cause for the swelling?

C. Like A, we do not care about females. It would work if the sex were switched.

D. seanky but wrong. It would have been an effective contender if the five revealed were as big as their female counterparts. This answer says bigger than the average. That there exists an average even means that the INs aren't all the same sizes and that some will be bigger than the average.

E. The region of the brain isn't linked to a certain type of disease so we can reasonably infer that the sub region of the brain isn't linked to this disease. X is a subtype of this disease. The connection of x to y and the disconnection from IN to Y weakens any link the author is trying to establish.

[Robert Carroll]

President,

Good overall! Let me examine each thing you said.

Answer choice (A): Because the conclusion is about male cats, statements about female cats are already on a bad footing because their relevance is not prima facie established. This answer doesn't do anything to prove its relevance, so it's wrong.

Answer choice (B): Since we know so little about disease Z, just about anything could be true about it! You're right, then, that maybe it is related to disease X in a way GOOD for the stimulus! Or not. We have no idea, so this answer does nothing.

Answer choice (C): I agree that, being about female cats, this has a special burden of proving relevance, like answer choice (A). But note that if it were about male cats, it would actually HELP the argument.

Answer choice (D): I don't think changing this answer to have the IN as large as a females would make any difference. This answer is showing that, of 1000 male cats who didn't have the disease, only a tiny amount had bigger-than-average INs. That...seems pretty consistent with the stimulus. Even if 5 had much, much bigger INs, it's still a tiny percent, which is quite compatible with the stimulus.

Answer choice (E): sounds good!

Robert Carroll

[lsatquestions]

I picked C and while I now understand why E is the better choice, I'd like a thorough explanation of why C is incorrect. My thinking was that if the nucleus is larger in female cats with the disease the same way it was for male cats, it may be the disease causing the larger nucleus (relationship reversed). Is that too much of a jump?