The interstitial nucleus, a subregion of the brain's hypothalamus, is

Question

The interstitial nucleus, a subregion of the brain's hypothalamus, is typically smaller for male cats than for female cats. A neurobiologist perFORMed autopsies on male cats who died from disease X, a disease affecting no more than .05 percent of male cats, and found that these male cats had interstitial nuclei that were as large as those generally found in female cats. Thus, the size of the interstitial nucleus determines whether or not male cats can contract disease X.

Which one of the following statements, if true, most seriously weakens the argument?

(A) No female cats have been known to contract disease X, which is a subtype of disease Y.

(B) Many male cats who contract disease X also contract disease Z, the cause of which is unknown.

(C) the interstitial nuclei of female cats who contact disease X are larger than those of female cats who do not contract disease X.

(D) Of 1,000 autopsies on male cats who did not contract disease X, 5 revealed interstitial nuclei larger than those of the average male cat.

(E) The hypothalamus is known not to be causally linked to disease Y, and disease X is a subtype of disease Y.

jon133 · Accepted Answer

This question is from the June 1999 LSAT (section 3, logical reasoning).

The credited response is E. I hated this question, and hated this answer choices. Narrowed my final selection down to D and E. Both answer choices seemed incredibly weak, leaving me to guess D.

However, after further reflection I realized that, if anything, D seemed to weaken the argument. If disease X affects no more than .05 percent of all male cats, and 1,000 autopsies are performed on male cats who  did not  contract the disease, finding only 5 of cats with larger interstitial nuclei would seem to support the idea that size affects the likelihood of contracting the disease (because the 995 cats with average sized nuclei did not contract it).

While, in hindsight, E seems slightly more compelling, the answer is so deceptively worded, lending to my frustration in connecting it to the the conclusion of the argument. The stimulus discusses the interstitial nucleus, noting that it is only a  subregion  of the hypothalamus. E states that the  hypothalamus itself  is known not to be linked to disease Y, of which X is a subtype. Confusing, but if the interstitial nucleus is a subregion of the hypothalamus I can see how the two could be considered one in the same (a similar argument could be made for the X/Y subtype classification).

An expectedly tricky question # 25.

sprtng · Answer

I will go with E, the passage states that bigger hypothalamus causes the possibility of contract the diseases X, but E denies it, thus weakens the argument

DanaJ · Answer

I too believe it's E and the reason for this is highlighted in red.

I don't think it's D because D states that the whatever nuclei  were larger than those of the average male cat  and not of the same size as those of female cats. What if indeed the male cats had larger nuclei, but they weren't nearly as large as those of females?

sssong · Answer

The interstitial nucleus , a subregion of the brain's hypothalamus,  is typically smaller for male cats than for female cats . A neurobiologist perFORMed autopsies on male cats who died from disease X, a disease affecting no more than .05 percent of male cats, and found that these male cats had interstitial nuclei that were  as large as those generally found in female cats . Thus, the size of the interstitial nucleus determines whether or not male cats can contract disease X.

(D) Of 1,000 autopsies on male cats who did not contract disease X, 5 revealed interstitial nuclei larger than those of the average male cat.
We are not concerned about whether the size of interstitial nucleus is larger than that of the "average male" cat. The argument compares size between male cats and female cats. So option D is irrelevant. Hope it's clear..

exc4libur · Answer

premise: typically, nuc males < nuc females,
premise: study on MALES with X had nuc males ≤ nuc fems;
con: study suggests that nuc males ≤ nuc fems determines whether the can get X.
assum: nuc males ≤ nuc fems = X; what if the inverse was true, X made the nuc males larger? or, what if the sample studied was an anomaly?…

(A) no fems "HAVE BEEN KNOWN" to get X <= this leaves an open possibility that fem cats with nuc similar to males got X, so this doesnt necessarily weaken; also, X could be only contracted by males, thus, this info would be irrelevant;
(B) irrelevant;
(C) again, this talks abt female cats, which leaves open the possibility that X acts differently in males; besides, this could strengthen the argument, suggesting that the size of nuc does determine getting X;
(D) 5 revealed a nuc "LARGER THAN THE AVG MALE" <= notice the comparison between males vs males… the argument's premise refers to nuc MALES vs nuc FEMALES; this might suggest that those 5 males, had a larger nuc than the average, but a smaller nuc than females!

Answer (E): if the hyp is KNOWN (fact) no to be linked to Y/X => then the argument falls, bc the author assumes that the nuc in the hyp determines getting Y/X.

VerbalBot · Answer

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The interstitial nucleus, a subregion of the brain's hypothalamus, is

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The interstitial nucleus, a subregion of the brain's hypothalamus, is

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