Q21 - Journalist: People whose diets

[ohthatpatrick]

What does the Question Stem tell us?
Strengthen

Break down the Stimulus:
Conclusion: Eating less iron-rich food should reduce your chance of getting Parkinson's.
Evidence: (correlation) People with a lot of iron in their diet are more likely to get Parkinson's than others.

Any prephrase?
Well, it's the ol' correlation -> causality show. There's a correlation between "more iron, higher Parkinson's risk", and the author assumes that "more iron" is CAUSING the "higher Parkinson's risk". When the author concludes some causal explanation/interpretation, we have two pressure points: "Is there some OTHER WAY we could explain/interpret the same evidence?" "Is the author's explanation/interpretation PLAUSIBLE?" In the specific world of correlation-causality, we often need to consider "Reverse Causality" as a different way to explain/interpret the correlation. Maybe having Parkinson's makes it more likely that you crave iron-rich foods? We could also consider "Other factors". Maybe people who eat high-iron diets have some other characteristic, and THAT characteristic is what's causing the higher Parkinson's risk. In terms of Plausibility of Author's story, you usually see answers that speak to whether cause/effect appear or disppear in tandem. A very common correct answer to a strengthen question would be an answer that shows "no cause, no effect".

Correct answer:
A

Answer choice analysis:
A) Yes. This rules out an alternative explanation. If people with a genetic predisposition to Parkinson's had higher iron in their diet, that would weaken the author's argument. We would see that the genetic predisposition was the CAUSAL factor, and the high iron diet was just some coincident factor. It's not like by eating less iron, these people could reduce their genetic predisposition to Parkinson's.

B) This is more of a Weaken answer (cause, no effect). It shows people ARE eating high iron but AREN'T getting Parkinson's.

C) This kids vs. adults distinction is competely irrelevant to the conversation.

D) Great. So what? This doesn't help us to evaluate whether more iron CAUSES more Parkinson's.

E) This is close to what (C) was doing. Why do we care about people's ages?

Takeaway/Pattern: Strengthen and Weaken are dominated by the pattern of Causal Explanations / Interpretations. When you're strengthening such an argument, you're either RULING OUT an alternative explanation or ADDING PLAUSIBILITY to the author's story.

#officialexplanation

[ganbayou]

I chose the correct answer but...
I thought even it is or it is not, predisposition is related the amount of iron, so it also indirectly talks about the relationship btw the disease and iron, isnt it?? so I thought the answer does not actually provide another reason...

[andreareed2007]

Can anyone provide a little more explanation for why A is correct? If because if you have a genetic predisposition, the level of iron you eat is irrelevant, doesn't that WEAKEN the journalists reasoning? Because it proves that limiting foods w/ iron in them doesn't reduce your chance of disease. By showing there are alternative causes, that SUPPORTS the stem's argument how?

Thanks!!!

[ohthatpatrick]

If we're given a correlation between X and Y,
and the author concludes X causes Y,

the most common type of LSAT objection is
"what if Z causes Y?"

Often, Z might be something that's riding X's coattails (or vice versa), so THAT'S why there's a correlation between X and Y, even though Z is the real causal factor.

e.g.
"People who eat a lot of expensive caviar are more likely than those who don't to own an expensive yacht. Therefore, eating caviar, the salty eggs of fish, must increase someone's desire to own a yacht."

We might say the real causal factor determining whether you own an expensive yacht is your wealth.

And with wealth comes the ability to eat expensive caviar.

Thus, WEALTH, is really what's causing the caviar habit and the yacht ownership, but it creates a correlation between caviar-eating and yacht ownership.

To strengthen the idea that caviar is the causal factor and rule out the idea that wealth is, we'd want an answer that says

"People who are wealthy enough to afford an expensive yacht are not more likely to eat caviar than people who aren't."

Similarly, for this question .. there is a correlation between high iron and Parkinson's,
and the author concludes that the high iron causes the Parkinson's.

We want to consider, among other things. "What if some third factor causes both the high iron and the Parkinson's? Maybe there's some genetic condition that leads to both high iron and the Parkinson's. In that case, it won't matter what you eat, because it's not the high iron causing the Parkinson's, it's just some genetic condition."

(A) is pushing back against that possibility by telling us "genetic causes of Parkinson's are NOT correlated with high iron".

If they were, we'd be Weakening the author by saying
"No, dum-dum. HIGH IRON isn't causing the Parkinson's, a GENETIC PREDISPOSITION is causing the Parkinson's. The reason there's a correlation between high iron and Parkinson's is simply because there's a correlation between the genetic predisposition and high iron."