LSAT 117 | Section 2 | Logical Reasoning: Q5

LR Question 5 Explanation

QUESTION TEXT: The corpus callosum–the thick band of nerve fibers …

QUESTION TYPE: Necessary Assumption

CONCLUSION: Musical training causes certain brain changes, especially when it starts young.

REASONING: Musicians tend to have larger corpora callosa than nonmusicians. This difference is especially noticeable in adult musicians who began training around age 7.

ANALYSIS: Professional basketball players are taller than average adults. So … basketball training makes people tall?

No! Maybe tall people are more likely to become basketball players.

It’s the same thing here. The argument sees a difference between musicians and nonmusicians and concludes that the musical training caused the brain difference.

But there’s another possibility: people who became musicians already had larger corpora callosa before training began.

If that were true, then musical training may not have caused the difference at all. Maybe children with larger corpora callosa are more likely to succeed at music or stick with training.

So the argument depends on assuming that musicians didn’t already have larger corpora callosa before they started training.

___________

1. CORRECT. This rules out the biggest alternative explanation. If musicians already tended to have larger corpora callosa before training, then the study would not show that training caused the difference.
   Negation: Musicians do tend to have bigger corpora callosa than nonmusicians before they start training.
2. Early training is especially associated with brain changes. That doesn’t require that late-life training causes no changes at all.
   Negation: Training late in life does cause brain changes.
3. We’re comparing musicians to nonmusicians, so we don’t need all early-trained musicians to have the same size corpus callosum.
   Negation: For any two musicians who began around the age of 7, their corpora callosa are not the same size.
4. Wayyy too strong. The argument only says musicians have larger corpora callosa on average. It doesn’t need every musician to have a larger one than every nonmusician.
   Negation: There is at least one musician who does not have a larger corpus callosum than a nonmusician.
5. The key issue is whether musicians already had larger corpora callosa before training. Even if nonmusicians did other activities, the training hypothesis could still be true.
   Negation: Adult nonmusicians did participate in activities that would stimulate growth when they were kids.