Logical ReasoningDifficulty: Medium

PT114 S4 Q18 Explanation

Anders: The physical structure of

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsRole

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Stimulus

Anders: The physical structure of the brain plays an important role in thinking. So researchers developing "thinking machines"—computers that can make decisions based on both common sense and factual on the structure of the brain.

Yang: Important does not mean essential. After all, no flying machine closely modeled on birds has worked; workable aircraft are structurally very different from birds. So thinking machines closely modeled on the brain are also likely to fail. In developing a workable thinking machine, researchers would therefore on the brain's function and simply ignore its physical structure.

What this question is testing

Role

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
18.

The statement “thinking machines closely modeled on the brain are also likely to fail” serves which one of the following

Answer choices

  1. Wrong Role22% picked this

    the main conclusion of the

    The Main Conclusion is the final sentence.

  2. Correct73% picked this

    a subsidiary conclusion used in support of the

    Why this is right

    We know it's a conclusion, because it's prefaced by "So". Does it help to support some other conclusion? Yes, it supports the final sentence, which uses the word "therefore" to indicate that its pulling its support from the 3rd sentence. Based on the fact that successful planes weren't modeled on the physical structure of birds (the ones that were failed), the author draws an intermediate conclusion that if we modeled thinking machines on the physical structure of the brain, they would probably also fail. Because thinking machines modeled on the brain's structure would probably fail, the author draws her final conclusion that we'd have better luck modeling these thinking machines on the function of the brain.

    Skill tested: Role · how this choice captures the argument's function is the move to repeat next time.

  3. Not a Principle1% picked this

    a principle of research invoked in support of

    This is an opinionated prediction being drawn on the basis of premises about the success rate of aircraft made to look or not look like birds. It's not a "principle of research".

  4. Not General Conclusion / Not Example3% picked this

    a particular example illustrating a general

    This is an opinionated prediction being drawn on the basis of premises about the success rate of aircraft that did / didn't resemble birds. It's not an example of anything. And the claim it supports (the final sentence) is not really a general claim. It's a specific recommendation regarding developing successful thinking machines.

  5. Not Background1% picked this

    background information providing a context for

    We know this is a conclusion because it's prefaced by "So". This conclusion is an opinionated prediction being drawn on the basis of premises about whether aircraft that was / wasn't modeled on birds was successful.

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