LSAT (Law School Admission Test)Logical ReasoningMedium
Biologist: A recent study found that the population of species X, a type of freshwater fish, has declined by 30% in Lake Verde over the last five years. During the same period, there has been a significant increase in the presence of an invasive aquatic plant, species Y, in the lake. Therefore, the decline in species X's population is most likely caused by the proliferation of species Y.
- AThe study failed to establish that the decline in species X began only after the significant increase in species Y.
- BThe study did not consider other potential factors that might affect the population of species X, such as changes in water temperature or the introduction of new predators.
- CThe study did not specify the exact mechanism by which species Y could harm species X, such as reducing oxygen levels or competing for food sources.
- DThe study did not compare the decline in species X in Lake Verde to its population trends in other lakes where species Y is not present.
Show answer & explanationAnswer & explanation
Correct answer: A. The study failed to establish that the decline in species X began only after the significant increase in species Y.
The biologist concludes a causal relationship based on correlation. To establish causation, especially when dealing with a decline and an increase, the timing of these events is crucial. If the decline in species X started before the increase in species Y, then Y cannot be the cause.
Why the other options are wrong
- B. While other factors could weaken the argument, this option introduces new information that the biologist didn't address, rather than pointing out a flaw in the biologist's conclusion based on the given information.
- C. While understanding the mechanism would strengthen the argument, it's not a prerequisite for concluding a causal link, especially in scientific observations where mechanisms are often discovered after the correlation is established.
- D. Comparing to other lakes could strengthen the argument by eliminating alternative causes specific to Lake Verde, but its absence is not a direct flaw in establishing a causal link from the given data.
Temporal Discrepancy (Causal Flaw)
A causal flaw where an argument incorrectly infers causation by failing to establish that the supposed cause occurred before or concurrently with the effect.
- Correlation does not imply causation.
- For A to cause B, A must precede or coincide with B.
- Observing a decline and an increase does not automatically mean one caused the other unless their timing aligns causally.
Memory trick: Time's Arrow: Cause must precede Effect.