LSAT Explanation PT 32, S1, Q12: Navigation in animals is defined as

LSAT Question Stem

Which one of the following, if true, casts the most doubt on the validity of the evidence offered in support of the naturalists' claim? 

Logical Reasoning Question Type

This is a Weaken question. 

Correct Answer

The correct answer to this question is B. 

LSAT Question Complete Explanation

The passage presents an argument about the navigational abilities of polar bears. The argument has the following structure:

Premise: Some naturalists claim that polar bears can navigate over considerable distances.

Evidence: They cite an instance of a polar bear that returned to its home territory after being released over 500 kilometers (300 miles) away.

Conclusion: Polar bears can navigate over considerable distances.

The question type is a Weaken question, asking us to find the answer choice that casts the most doubt on the validity of the evidence offered in support of the naturalists' claim.

Before discussing the answer choices, let's come up with an "Evaluate" question about the argument: "Was the released polar bear in unfamiliar territory when it began its journey home?"

Now, let's analyze each answer choice:

a) The polar bear stopped and changed course several times as it moved toward its home territory.

This answer choice doesn't necessarily weaken the argument. Stopping and changing course could be part of the polar bear's navigational process, or it could be due to other factors, such as obstacles or resting. It doesn't provide enough information to cast doubt on the polar bear's navigational abilities.

b) The site at which the polar bear was released was on the bear's annual migration route.

This is the correct answer. It weakens the argument by suggesting that the polar bear was not in unfamiliar territory when it began its journey home. If the bear was on its annual migration route, it might already know the way, which would mean that the instance cited doesn't demonstrate navigation as defined in the passage.

c) The route along which the polar bear traveled consisted primarily of snow and drifting ice.

This answer choice doesn't weaken the argument, as it doesn't provide any information about the polar bear's navigational abilities or the familiarity of the territory. It merely describes the environment the bear traveled through.

d) Polar bears are only one of many species of mammal whose members have been known to find their way home from considerable distances.

This answer choice doesn't weaken the argument, as it doesn't challenge the polar bear's navigational abilities. It merely states that other species also have similar abilities, which doesn't cast doubt on the evidence provided for polar bears.

e) Polar bears often rely on their extreme sensitivity to smell in order to scent out familiar territory.

This answer choice doesn't weaken the argument because it doesn't provide information about the polar bear's ability to smell over such a long distance (300 miles). While it suggests that polar bears use their sense of smell to find familiar territory, it doesn't contradict the definition of navigation or the evidence provided.

In conclusion, the correct answer is B, as it casts doubt on the validity of the evidence by suggesting that the polar bear was not in unfamiliar territory when it began its journey home.