Logical reasoning PrepTest 106 · Section 2 · Question 8

Question prompt

The symptoms of mental Remaining source text redacted.
Why the credited answer is right

Credited answer: A

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Argument

Valid or Flawed

Flawed

Question Type

Strengthen with Necessary Premise Questions

Stimulus Summary

Some mental disorders are caused by chemical imbalances, so they can be treated only with medication.

Answer Anticipation

Many questions on the LSAT are made a lot easier when you narrow the scope by seeing that the conclusion is narrower than the scope of the premises. Here, the argument pivots (“But”) and reaches a conclusion about “these patients” - the ones that have mental disorders caused by chemical imbalances. The conclusion is that these patients can be treated only by medications. This conclusion highlights two things. First, we should focus only on the statements after the pivot, as the author isn’t relying on information before that pivot to reach the conclusion. And second, there’s a new concept in the conclusion - treatment by medication. When we are given a new concept in a Necessary Premise question, it’s almost always connected to the correct answer. So what’s the argument assuming here? Well, it argues that some mental disorders are caused by chemical imbalances. It then concludes that these can be treated only by medications. That assumes that a chemical imbalance can be treated only with medication, and not with any other treatment. Let’s find an answer reflecting that assumption.

Answer choices

  1. A
    Treatment by psychotherapy can Remaining source text redacted.
    Why choice A matches the stem
    This answer establishes that an alternative treatment to medication doesn’t work for “these patients” who have mental disorders caused by chemical imbalances. If psychotherapy can correct chemical imbalances, then medication isn’t the “only” treatment for them. This answer is therefore a necessary premise.
  2. B
    Treatment with medication always Remaining source text redacted.
    Why choice B is not credited
    The speed of treatment is out of scope - the argument cares only about efficacy.
  3. C
    Most mental disorders are Remaining source text redacted.
    Why choice C is not credited
    The relative prevalence of mental disorders caused by chemical imbalances isn’t relevant - what matters is what serves as an effective treatment for them. Maybe if we learned that most patients with mental disorders are effectively treated with psychotherapy would this be a necessary premise, but we learn that only “[s]ome” can be.
  4. D
    Medication is always more Remaining source text redacted.
    Why choice D is not credited
    Medication needs to be more effective for treating mental disorders than psychotherapy only for disorders caused by chemical imbalances for the argument to work, not for all mental disorders.
  5. E
    Treatment with psychotherapy has Remaining source text redacted.
    Why choice E is not credited
    As long as psychotherapy doesn’t correct chemical imbalances, the argument can hold together. If it works by reducing symptoms and inducing lifestyle changes, for instance, the argument holds together.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A Credited 91%
  2. B 2%
  3. C 3%
  4. D 3%
  5. E 1%

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