LSAT 157 | Section 2 | Logical Reasoning: Q20

LR Question 20 Explanation

QUESTION TEXT: The olecranon process is a bony part of the mammalian…

QUESTION TYPE: Flawed Reasoning

CONCLUSION: Megatherium was probably a predator.

REASONING: Mammals with shorter olecranon processes can typically move their forelimbs faster. Predatory mammals must move their forelimbs fast, and typically have short olecranon processes. Megatherium has short olecranon processes.

ANALYSIS: The flaw in this argument is that it takes an attribute of one group (predatory mammals) and assumes that anything with that attribute is part of that group. Megatherium’s short olecranon processes don’t automatically mean it was a predator!

Compare this to my classic example. I’ve rewritten the passage below, except I made it about cats and tails. If you can see the error here, you can do it in the stimulus too!

Tails can occur at the end of a mammal’s body and provide balance. Cats generally have tails. It’s recently been discovered that pigs have tails. It’s likely, therefore, that pigs are cats.

___________

1. CORRECT. The author assumes, without justification, that most mammals with short olecranon processes are predators.
2. It doesn’t actually matter for the argument why predators have short olecranon processes.
3. We really don’t care how effective Megatherium would be if it was different. It’s not relevant to the argument.
4. The author’s argument isn’t based on comparisons between olecranon processes of extinct and living mammals, so the inability to address this is not a flaw.
5. Once again, similar to B, the effects of a short or long olecranon process do not matter at all to the argument – only that a short one is associated with predators.

Recap: The question begins with “The olecranon process is a bony part of the mammalian”. It is a Flawed Reasoning question. Learn more about LSAT Flaw questions in our guide to LSAT Logical Reasoning question types.