Logical Reasoning

PT152 · S1 · Q8 Monarch butterflies must contend with

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Monarch butterflies must contend with single-celled parasites that can cause deformities that interfere with their flight.

Conclusion (this shows that)

Migrating allows monarch butterflies to avoid these single-celled parasites that can cause deformities that interfere with their flight.

Evidence

In populations that have not migrated, up to 95% are infected by parasites. In populations that do migrate, less than 15% are infected.

Evaluate

The evidence is look at an asymmetric comparison (i.e. a Curious Fact) and concluding a causal interpretation (migrating causes monarchs to avoid these parasites).

As always, we're supposed to react to this on Flaw primarily by considering Alternative Explanations for the curious fact.

Whenever the author presents a correlation, and then concludes that the first things causes the second "migration causes them to avoid parasites", we have two alternate explanations we always consider:

Reverse Cause? (could it be that avoiding parasites allows them to migrate? That could make sense. If you're infected by the parasite, it causes deformities that interfere with flight, so you wouldn't be able to migrate. That would explain why there's a correlation between infected and non-migrating. The infection comes first and prevents the migration!)

Third Factor? (could there be some 3rd factor we haven't identified yet that both increases the likelihood of migrating and decreases the likelihood of parasite infection?)

Goal

Because this question stem is prefaced with "fails to consider / overlooks the possibility", we basically want to treat these answers like Weaken.

The correct answer could attack the author's causal conclusion by suggesting an Alternate Explanation for the correlation between migrating and having low incidence of parasite infection. Or it could attack the plausibility of the author's story that migrating allows monarchs to avoid these parasites.

But the Reverse Cause alternate explanation seems highly likely, since it would be very logical to interpret these correlations as .

The reasoning in the argument is flawed in that the argument overlooks the possibility that

monarch butterflies are unable to
No Impact
This doesn't provide an Alternate Explanation for why there's a correlation between migrating and not-being-infected with parasites. This also doesn't say anything that hurts the plausibility that migration helps the monarchs to avoid these parasites.
6% picked this
long migrations are no better
Unclear Impact
Does this hurt the plausibility of the idea that migrations allow monarchs to avoid these parasites? Not really. Do the migrations need to be of a certain length in order to help protect the butterflies? It's not clear what length that would be or why that would make a difference in terms of parasite-protection. There might be one month (let's say January) when the parasites thrive. If a butterfly has migrated away during January, it will be protected from the parasites, whether that butterfly is gone for a short 3 month migration or for a long 6 month migration.
1% picked this
populations of monarch butterflies that
No Impact
The relative size of these populations doesn't matter. If we find out that 95% of left handed people get a disease X, while less than 15% of right handed people get disease X, we have good reason to suspect that disease X is connected to the genes that result in left-handedness. It doesn't make any difference that there are 8x as many right handed people in the world.
9% picked this
Correct
monarch butterflies infected with parasites
Why this is right
This provides the reverse cause Alternate Explanation we anticipated. It's not that migrating allows monarchs to avoid these parasites. It's that avoiding these parasites allows monarchs to migrate. We see arguments like, "People who attend exercise classes tend to be in better health than those who don't. Thus, exercise classes help improve your health", and LSAT wants us to consider the alternate, reverse cause interpretation of that correlation: maybe being healthy allows someone to attend an exercise class.
Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.
83% picked this
populations of monarch butterflies tend
No Impact
Why populations do or don't tend to migrate doesn't matter to us, unless the basis for that decision relates to whether or not a butterfly population would have significant exposure to the parasites. But there's no common sense connection between whether or not a population has a stable food source and whether or no they're exposed to this parasite.
1% picked this

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