LSAT 109 – Section 3 – Question 20

LSAT 109 - Section 3 - Question 20

December 2000

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT109 S3 Q20
+LR
Strengthen +Streng
Causal Reasoning +CausR
A
5%
164
B
3%
164
C
2%
161
D
89%
167
E
2%
160
120
134
150
 +Easiest 148.18 +SubsectionMedium

Galanin is a protein found in the brain. In an experiment, rats that consistently chose to eat fatty foods when offered a choice between lean and fatty foods were found to have significantly higher concentrations of galanin in their brains than did rats that consistently chose lean over fatty foods. These facts strongly support the conclusion that galanin causes rats to crave fatty foods.

Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that galanin makes rats crave fatty foods. Why? Because an experiment showed a correlation: rats who preferred fatty foods also had higher galanin concentrations in their brains.

Notable Assumptions
The author assumes the correlation results from one particular causation: that lots of brain galanin causes rats to crave fatty foods. This means assuming there’s no other cause for that correlation, such as the reverse causation: that eating fatty foods causes galanin to build up in rats’ brains.

A
The craving for fatty foods does not invariably result in a rat’s choosing those foods over lean foods.
This doesn’t affect the argument. Rats could have “consistently” chosen fatty food without choosing it every single time.
B
The brains of the rats that consistently chose to eat fatty foods did not contain significantly more fat than did the brains of rats that consistently chose lean foods.
This is irrelevant. The author makes no claim about fat inside the rats’ brains—only the fat in their food and the galanin in their brains.
C
The chemical components of galanin are present in both fatty foods and lean foods.
This doesn’t mean the fatty and lean diets contained similar amounts of galanin. This is fully compatible with the reverse causation: the rats who preferred fatty foods simply consumed more galanin in their diets.
D
The rats that preferred fatty foods had the higher concentrations of galanin in their brains before they were offered fatty foods.
This strengthens the argument by casting doubt on an alternative explanation. It makes the reverse causation—that rats had lots of galanin in their brains because of their high fat intake—less likely.
E
Rats that metabolize fat less efficiently than do other rats develop high concentrations of galanin in their brains.
This detail is compatible with the conclusion, but it doesn’t strengthen the argument. It’s just as compatible with the reverse causation: rats who metabolize fat less efficiently crave fattier foods, and that higher fat consumption causes galanin to build up in their brains.

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LSAT PrepTest 109 Explanations

Section 1 - Logical Reasoning

Section 2 - Reading Comprehension

Section 3 - Logical Reasoning

Section 4 - Logical Reasoning

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