LSAT Explanation PT 38, S4, Q19: Anders: The physical structure of the

LSAT Question Stem

In evaluating Yang's argument it would be most helpful to know whether 

Logical Reasoning Question Type

This is an Evaluate question. 

Correct Answer

The correct answer to this question is A. 

LSAT Question Complete Explanation

Let's first analyze the passage's argument structure. Yang's argument can be broken down as follows:

Premise 1: Important does not mean essential.

Premise 2: No flying machine closely modeled on birds has worked; workable aircraft are structurally very different from birds.

Premise/Subconclusion: So thinking machines closely modeled on the brain are also likely to fail.

Conclusion: In developing a workable thinking machine, researchers would increase their chances of success if they focus on the brain's function and simply ignore its physical structure.

The question type for this problem is "Evaluate" which asks us to identify the missing crucial information in the argument that determines its validity.

Now, let's discuss each answer choice:

a) studies of the physical structure of birds provided information crucial to the development of workable aircraft

- This is the correct answer. Using the Variance Test:

- If "Yes, they did provide crucial information," then developers should not ignore the physical structure of the brain because the reasoning used to make that judgment (via the flying machine analogy) is faulty.

- If "No, they did not provide crucial information," then the argument is strengthened because the analogy suggests it would be acceptable to ignore the physical structure of the brain.

b) researchers currently working on thinking machines take all thinking to involve both common sense and factual knowledge

- This answer is incorrect because the conclusion is about ignoring the physical structure of the brain, and information about what constitutes thinking will not help evaluate the argument. Apply the Variance Test with opposite answers of "Yes" and "No" to disprove this answer.

c) as much time has been spent trying to develop a workable thinking machine as had been spent in developing the first workable aircraft

- This answer is incorrect because the relative amount of time spent on each project is not an issue in the stimulus. Apply the Variance Test with opposite answers of "Yes, as much time was spent" and "No, not as much time was spent" to disprove this answer.

d) researchers who specialize in the structure of the brain are among those who are trying to develop thinking machines

- This answer is incorrect because the argument does not involve the background of the researchers and the projects they work on, only what they should focus on when trying to succeed. Apply the Variance Test with opposite answers of "Yes, they are among those trying to develop thinking machines" and "No, they are not among those trying to develop thinking machines" to disprove this answer.

e) some flying machines that were not closely modeled on birds failed to work

- This answer is incorrect because the analogy in the argument is about flying machines that were modeled on birds. The possibility that some flying machines that were not modeled on birds failed has no place in the argument. Apply the Variance Test with opposite answers of "Yes, some failed" and "No, none failed" to disprove this answer.