Logical Reasoning

PT117 · S2 · Q5 The corpus callosum—the thick

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The corpus callosum—the thick band of nerve fibers connecting the brain’s two hemispheres—of a musician is on average larger than that of a nonmusician.

Conclusion (therefore)

Musical training, particularly when it begins at a young age, causes certain anatomic brain changes.

Evidence

The corpus callosum of musicians, particularly those of adults who began training around age 7, are larger on average than those of adult nonmusicians.

Evaluate

This is a classic Causation Flaw: we have evidence of a correlation between two things and conclude that one of them must have caused the other.

Anticipate

This sort of Causation Flaw typically overlooks the reverse causality objection: what if the larger corpus callosum isn't the effect of early musical training but something that causes someone to want, or respond well to, that training? The correct answer might neutralize that objection by saying that a big ol' corpus callosum doesn't help you become a musician. But it also might do any number of other things because Necessary Assumption questions aren't consistently predictable, so read every answer with an open mind.

5.

Which one of the following is an assumption on which the argument depends?

  1. Correct

    The corpora callosa of musicians,

    Why this is right

    Boom! A match for our prediction. This neutralizes the reverse causality objection by showing that the corpus callosa of musicians isn't already big before they begin training. We could also think of this answer as establishing a control group. In the absence of the purported cause (musical training), we don't see the purported effect (the bigger corpus callosa).

    Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

    77% picked this

  2. Musical training late in life

    Inverse Bait

    This argument hinges on the idea that music training early in life does cause anatomic changes to the brain. But that doesn't also assume that music training late in life does not cause anatomic changes. This is a classic LSAT trap!

    9% picked this

  3. For any two musicians whose

    Irrelevant Comparison: any two musicians

    This argument compares musicians to non-musicians. We don't need to assume anything about how two musicians compare to one another. This is also really strong. The universal quantifier "any" is always a red flag on Necessary Assumption questions because most LSAT arguments are built to withstand at least a few non-conforming cases.

    4% picked this

  4. All musicians have larger corpora

    Too Strong: all / any

    The universal quantifiers "all" and "any" are always red flags on Necessary Assumption questions because most LSAT arguments are built to withstand at least a few non-conforming cases. Also, we're already told that musicians have, on average, a larger corpora callosa than nonmusicians. We don't need to assume that every individual within those two groups also compares in that way in order to draw our conclusion.

    3% picked this

  5. Adult nonmusicians did not participate

    Too Strong: any

    The universal quantifier "any" is always a red flag on Necessary Assumption questions because most LSAT arguments are built to withstand at least a few non-conforming cases. Would it mess up this argument if one adult nonmusician did participate in an activity as a child that stimulated a little growth of ye olde corpus callosum? Not at all, because the averages put forth in the evidence aren't compromised by that.

    7% picked this

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