LSAT Explanation PT 28, S1, Q21: Psychologist: Some astrologers claim that our
LSAT Question Stem
Which one of the following is an assumption on which the psychologist's argument depends?
Logical Reasoning Question Type
This is a Necessary Assumption question.
Correct Answer
The correct answer to this question is C.
LSAT Question Complete Explanation
In this passage, the psychologist is arguing against the claim made by some astrologers that our horoscopes completely determine our personalities. The psychologist presents a counterexample: two individuals who were born on the same day and at exactly the same time 40 years ago, but in different locations (Toronto and New York). The psychologist points out that these two individuals have different personalities, which is used as evidence against the astrologers' claim. The structure of the argument is as follows:
Premise: Two individuals were born at the same time but in different locations (Toronto and New York), and they have different personalities.
Conclusion: Our horoscopes do not completely determine our personalities.
The question is a Necessary Assumption question, which asks us to identify an assumption on which the psychologist's argument depends. The correct answer is C, which states that the geographical difference between Toronto and New York did not result in the two individuals having different horoscopes.
Now let's analyze each answer choice in more detail:
A) Astrologers have not subjected their claims to rigorous experimentation.
- This answer choice is not a necessary assumption for the psychologist's argument. Even if astrologers had subjected their claims to rigorous experimentation, the psychologist's counterexample could still be valid.
B) The personality differences between the two individuals cannot be explained by the cultural differences between Toronto and New York.
- While this answer choice may seem plausible, it is not a necessary assumption for the psychologist's argument. Even if cultural differences could explain the personality differences, it would not affect the conclusion that horoscopes do not completely determine our personalities.
C) The geographical difference between Toronto and New York did not result in the two individuals having different horoscopes. (Correct Answer)
- This answer choice is a necessary assumption for the psychologist's argument. If the geographical difference did result in different horoscopes, then the psychologist's counterexample would be invalidated, as the different personalities could still be attributed to different horoscopes.
D) Complete birth records for the past 40 years were kept at both hospitals.
- This answer choice is not a necessary assumption for the psychologist's argument. The accuracy of these two specific individuals' birth records is more important than the completeness of all birth records at both hospitals.
E) Identical twins have identical genetic structures and usually have similar home environments.
- This answer choice is not a necessary assumption for the psychologist's argument. Even if this statement were not true, the psychologist's counterexample of the two individuals born at the same time but in different locations would still be valid.
In summary, the correct answer is C, as it is a necessary assumption for the psychologist's argument. If the geographical difference between Toronto and New York resulted in different horoscopes, the psychologist's counterexample would be invalidated, and the conclusion that horoscopes do not completely determine our personalities would be undermined.