Psychologist: Some astrologers claim that our horoscopes completely determine our personalities, but this claim is false. I concede that identical twins—who are, of course, born at practically the same time—often do have similar personalities. However, birth records were examined to find two individuals who were born 40 years ago on the same tests revealed that the personalities of these two individuals are in fact different.
What this question is testing
Your task
Find the assumption the argument requires in order for its conclusion to hold.
Common trap
Answers that would help the argument but aren't strictly required (sufficient, not necessary).
Winning move
Negate each choice — the right one breaks the argument when negated.
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