LSAT 137 | Section 3 | Logical Reasoning: Q13

LR Question 13 Explanation

QUESTION TEXT: Psychologist: Identical twins are virtually the same…

QUESTION TYPE: Weaken

CONCLUSION: Many of our tendencies are genetic, not environmental.

REASONING: Identical twins are more or less genetically identical. And when raised separately, they tend to grow up into people who report having similar ethics, styles of dress, and jobs.

ANALYSIS: This author is saying genetics, not environment, are the cause. To weaken the argument, we should show the environment has an impact in some way.

Genes don’t make for a relevant answer. We know genes can’t be changed, and we must accept the argument’s evidence that identical twins have the same genes. Note that it doesn’t matter why genes have an effect. The argument is only about whether they do.

___________

1. So? This might mean that both identical twins have the same midlife crisis at 40.
2. This doesn’t matter. The conclusion was that many of our inclinations are genetic. The argument isn’t saying that all of them need to be genetic.
3. We don’t care why genes have an effect. Things can have effects even if we don’t understand why.

4. CORRECT. This shows the environment has caused these differences. We now have two cases:

   • When twins are apart, they become similar (stimulus)
   • When twins are together, they become different (this answer)

   Based on these two cases, an environmental change causes a change in inclinations. So environment, not genetics, is the cause.

5. So? Non-identical twins presumably have different genes. Those different genes could be the cause of the differences in inclination.