LSAT 106 – Section 3 – Question 25

LSAT 106 - Section 3 - Question 25

June 1999

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT106 S3 Q25
+LR
Weaken +Weak
Causal Reasoning +CausR
A
6%
165
B
8%
164
C
12%
164
D
29%
165
E
45%
170
162
169
177
 +Hardest 148.198 +SubsectionMedium

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.

Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the size of the interstitial nucleas determine whether a male cat can contract disease X. This is based on data showing that male cats who died from disease X have larger interstitial nuclei than those male cats that didn’t die from disease X.

Notable Assumptions
The author assumes that the correlation observed between the size of the interstitial nucleus in male cats and death from disease X must be explained by the size of the interstitial nucleus having a causal impact on the presence of disease X.

A
No female cats have been known to contract disease X, which is a subtype of disease Y.
The conclusion is just about male cats’ susceptibility to disease X based on their interstitial nucleus size. Whether female cats can get disease X doesn’t impact the author’s reasoning, which was limited only to what we observed in male cats.
B
Many male cats who contract disease X also contract disease Z, the cause of which is unknown.
This establishes that many cats that get X also get Z. But this doesn’t provide any insight into the cause of disease X in male cats.
C
The interstitial nuclei of female cats who contract disease X are larger than those of female cats who do not contract disease X.
This is additional data suggesting a correlation between a larger interstitial nucleus and contracting disease X. This is consistent with the author’s reasoning.
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.
This shows that a tiny percent of male cats without disease X had a larger interstitial nucleus. But we already know that all the male cats with disease X had this larger feature. So, (D) shows that there is a correlation between disease X and a larger interstitial nucleus.
E
The hypothalamus is known not to be causally linked to disease Y, and disease X is a subtype of disease Y.
The first sentence told us that the interstitial nucleus is a part of the hypothalamus. If the hypothalamus isn’t known to be a cause of Y, which includes subtype disease X, this suggests the interstitial nucleus isn’t a cause of disease X.

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LSAT PrepTest 106 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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