LSAT 16 - Section 3 - Question 18

This is a weakening question, we know this because the question stem asks: Which one of the following, if true, weakens the researchers’ argument?

This stimulus has the common LSAT trope of “some people used to believe X, now they believe Y, because of Z.” Our job is to weaken Z. Before scientists assumed that all Dinosaurs were cold-blooded like modern reptiles, but now they believe some may have been warm-blooded because there are fossils in the northern arctic and it is too cold there for cold-blooded animals. The conclusion is a hypothesis meant to explain how dinosaur fossils could be found in the arctic if cold-blooded animals can’t survive the winter there. This argument has some large assumptions it makes to reach the warm-blooded hypothesis; for example, that the dinosaurs remained in the arctic all year long, and that the climate was the same then as it is now. A good answer is going to pick up on one of these assumptions and undermine it, directly weakening the relationship between the support and the conclusion. Let’s take a look at the answer choices:

Answer Choice (A) This supports the argument. Since the stimulus tells us that all of today's reptiles are cold blooded, all this answer adds is that most are confined to particularly warm climates, further strengthening the relationship between cold-blooded animals and warm climates.

Answer Choice (B) This answer brings in size, hoping to get you thinking about how size might relate to the ability to survive in cold environments. The truth is that we just aren’t given any information about how size might relate to the scientist's conclusion, and therefore are not entitled to make any inferences that might weaken the argument.

Answer Choice (C) If the stimulus claimed that Dinosaurs couldn’t have lived in the arctic because there was nothing for them to eat, then the existence of cold-resistant plants might be relevant; but it specifically states that the issue is that cold-blooded animals would freeze to death in an arctic winter. This answer is particularly bad because the plants having been cold resistant further suggests that the arctic was extremely cold in the past as well, which is an assumption that supports the scientists argument.

Correct Answer Choice (D) This answer picks up on one of the assumptions we identified in the stimulus; that the dinosaurs remained in the arctic in all seasons. The researchers’ support specifically states that it is the arctic winters that are the problem. A fossil does not tell us in what season the animal died and whether it lived all year in the area in which it died. This answer undermines this assumption that the dinosaurs lived in the arctic during the winter, from which the researcher’s draw their warm-blooded hypothesis. If the dinosaurs would need to continually migrate, we have a reason to believe they may not have remained in the arctic during the winter and hence may have been cold-blooded like all other reptiles.

Answer Choice (E) This would be a good answer if it were a strengthening question. Like D it picks up on an assumption the argument makes, in this case that the arctic climate was similar during the period of the Dinosaurs. By explicitly stating that it was in fact similar, it directly strengthens the warm-blooded hypothesis.