Logical ReasoningDifficulty: Medium

PT13 S4 Q17 Explanation

Recent research shows that hesitation

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

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Stimulus

Recent research shows that hesitation, shifting posture, and failure to maintain eye contact are not reliable indicators in discriminating between those who are lying and those who are telling the truth. The research indicates that behavior that cannot be controlled is a much better clue, at least when the lie is important and small movements of facial muscles, which indicate distress, fear, or anger.

What this question is testing

Weaken

Your task

Find the choice that makes the argument's conclusion less likely to be true.

Common trap

Answers that look negative but attack a claim the argument never relied on.

Winning move

Find the assumption the argument depends on, then pick the choice that undermines it.

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

The question
17.

Which one of the following provides the strongest reason for exercising caution when relying on the “better” clues mentioned above in order to discover

Answer choices

  1. No Impact7% picked this

    A person who is lying might be aware that he or she is being closely observed

    While awareness of being observed might influence behavior, the argument centers on "uncontrollable" behavior like pupil dilation, which should ideally not be influenced by awareness. Therefore, this doesn't provide a strong reason against these clues' reliability.

  2. No Impact0% picked this

    Someone who is telling the truth might nevertheless have a past

    This answer has nothing to do with whether the plan of checking pupils / facial muscles would help us assess whether someone is presently lying.

  3. No Impact14% picked this

    A practiced liar might have achieved great control over body posture

    This choice doesn't address the reliability of the uncontrollable indicators. Control over posture and eye contact relate to the dismissed unreliable clues, not the "better" ones.

  4. Correct74% picked this

    A person telling the truth might be affected emotionally by being suspected of lying or by some other

    Why this is right

    If someone telling the truth becomes emotionally affected by suspicion or the situation, they might exhibit similar physiological responses—like pupil dilation and facial muscle movements—as a liar. There was a Breadcrumb telling us that pupil dilation is caused by emotional arousal, and this answer is saying that the truth-tellers might also get emotionally aroused. So if we see dilated pupils, we won't know whether they were caused by the emotional arousal of "being stressed about your lies" or the emotional arousal of "being wrongly suspected as a liar".

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

  5. No Impact4% picked this

    Someone who is lying might exhibit hesitation and shifting posture as well

    This seems to suggest that in some cases both method 1 and method 2 would be eligible, but it doesn't give us any way to argue that one method is better / worse than the other.

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