LSAT 78, Logical Reasoning II, Q21, LSATHacks

QUESTION TEXT: Journalist: People whose diets contain a relatively…

QUESTION TYPE: Strengthen

CONCLUSION: You can lower your risk of getting Parkinson’s disease by eating less meat, seafood and other foods rich in iron.

REASONING: There is a correlation between a diet high in iron and Parkinson’s disease.

ANALYSIS: This argument shows a correlation. Whenever there’s a correlation, there are four possibilities:

1. Iron causes Parkinson’s.
2. Parkinson’s causes people to eat more iron.
3. Some third factor causes both Parkinson’s and makes people crave iron.
4. It’s a coincidence.

You can strengthen the argument by eliminating an alternative possibility. Note that the right answer is rather subtle.

___________

1. CORRECT. This eliminates an alternate cause. Specifically, number three in the list above. This answer eliminates the possibility that a genetic predisposition both causes Parkinson’s and also is associated with people eating more iron.
2. So? The argument didn’t limit itself to meats. They said “foods high in iron”.
   (Note: this answer isn’t saying “vegetarians don’t get Parkinson’s” or even “vegetarians are less likely to get Parkinson’s. The key factor is iron, not meat.)
3. So? This is just a fact about iron needs. It doesn’t strengthen the idea that iron-rich foods will cause Parkinson’s.
4. We are trying to strengthen the idea that reducing iron intake will reduce Parkinson’s risk. This answer doesn’t do that: if anything, it shows an additional factor that suggests in certain cases, reducing foods rich in poorly absorbed iron wouldn’t help much. 
5. So? The argument’s point was that lower is better. The argument wasn’t saying people will go lower, they were just saying what would happen if they did.

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