Logical reasoning PrepTest 137 · Section 3 · Question 13

Incorrect. There's no indication that these radical changes can't also be genetically determined.

Incorrect. The stimulus never connects economic needs to happiness, so this answer isn't supported and thus doesn't complete the argument.

Incorrect. There doesn't need to be a 1:1 connection directly established for a conclusion about genetic origin of inclinations to exist or be believed. If all reasonable alternatives are ruled out, then the conclusion could still be validly drawn.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Identical twins have the same genes. Some separated at birth have the same personality traits. Therefore, personalities are genetically determined, not subject to environmental influence.

Answer Anticipation:
Ah, the age-old debate nature vs. nurture. Do our genes determine who we are, or is it our environment? Here, the Psychologist sides with nature—"our inclinations are genetic" and "not subject to environment."

While the example of identical twins separated at birth certainly suggests that nature—genes—plays some role in determining our personalities, that's a far cry from saying that our personalities are "not subject" to nurture. In reaching that extreme conclusion, the Psychologist is ignoring that, while genetics may play a major role in this, nurture could still play some role, at least in some circumstances. Any answer that raises a time when nurture played a role in determining someone's inclinations will weaken this conclusion.

Answer Explanation:
This answer highlights the supposed cause—two people with the same genes—but the opposite outcome—differences, driven by the alternative cause of trying to differentiate themselves from each other. While the example of the twins split at birth certainly suggests that genes play a role, this example suggests that environment does, as well, so the conclusion that inclinations are "not subject to environmental influences" is too extreme, and therefore invalid.

Key Takeaway:
If you've ever heard the phrase "nature vs. nurture," then you've heard about the subject of this stem. The LSAT loves to bring up arguments based on this age-old debate, and the author of these arguments generally concludes that something is genetically determined, or something is determined by one's environment. What they always neglect to consider—and what the correct answer usually leans into—is that it's likely a little bit of both. Here, in declaring that something is "not subject to environmental influences," the author was ruling out any influence of environment, so any indication that environment could influence personality would undermine the conclusion.

Incorrect. Assuming that the "average" non-identical twins grow up in the same household (probably a valid assumption), then this brings up a group that has different genes but the same environment. Since they turn out differently, if anything, this is an example in the "genetically determined" column, supporting the author's argument.