LSAT 155 | Section 2 | Logical Reasoning: Q26

LR Question 26 Explanation

QUESTION TEXT: The three-spine stickleback is a small fish that lives…

QUESTION TYPE: Weaken

CONCLUSION: Having a larger size is a better defence against lake predators than having armor.

REASONING: Ocean stickleback have armor to protect them from predators, but lake stickleback don’t. Not having armor allows the lake stickleback to grow larger.

ANALYSIS: We have two types of fish here: lake stickleback and ocean stickleback. Ocean stickleback have armor, and lake stickleback do not. The lack of armor allows lake stickleback to grow larger, and the author uses this to conclude that being bigger must be a greater benefit against predators than armor. The correct answer will show that the author’s reasoning is not correct.

One way would be to show that the larger size has a benefit to the lake fish for something other than evading predators. Another way would be evidence that missing armor has a different benefit other than being large – maybe the armor slows the fish down, so having no armor allows them to evade the lake predators because of their faster swim speed.

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1. This almost looks like the second potential weakening we outlined above. However, this doesn’t weaken the argument because we don’t know that the lake predators are fast-moving. Without that information, we can’t conclude that being faster has a benefit in the lake and not the ocean.
2. CORRECT. The bigger size doesn’t help against predators, it helps the lake stickleback survive the winter. The winter might be a greater threat to survival than predators.
3. This doesn’t weaken the argument. It doesn’t tell us that the large size isn’t to better deal with predators, it just tells us that the predators are different.
4. This tells us nothing about why the lake fish might not need its armor as much as the ocean fish.
5. This also tells us nothing about why the lake fish doesn’t need armor, or what the benefits of not having armor might be.

Recap: The question begins with “The three-spine stickleback is a small fish that lives”. It is a Weaken question. Learn more about LSAT Weaken questions in our guide to LSAT Logical Reasoning question types.