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Complete Question Explanation

Assumption—CE. The correct answer choice is (A)

In this stimulus, the author discusses the correlation of two variables and incorrectly concludes that a
causal relationship exists:
  • Premise: Musician adults trained from childhood have, on average, larger corpus callosa than
    adult non-musicians.

    Conclusion: Therefore musical training must cause these differences in the brain.
This argument is flawed, because the author attempts to draw a causal conclusion (that musical training
increases corpus callosum size), where only a correlation between the two variables has been shown.
Since this is a Cause/Effect question, we should consider other possibilities. Perhaps there is some other
variable at work, causing both an enlarged corpus and a predisposition to music. Or perhaps cause and
effect have been reversed, and in reality having a larger corpus callosum predisposes one to take up
music.

Since this is an assumption question, we can apply the Assumption Negation technique by seeking a
response which, when negated, weakens the causal argument.

Answer choice (A): This is the correct answer choice. Negating this choice, if the corpus callosa
of musicians were naturally larger, the argument would fail. Thus the argument must assume that the
corpus collasa are initially similarly sized.

Answer choice (B): The argument concludes that musical training in general causes changes in the brain,
and that the effect is particularly pronounced when training begins at an early age. This response states
that music training at older ages cannot cause anatomic brain changes, which is somewhat contrary to
the author’s argument. Therefore this cannot be an assumption required by the argument.

Answer choice (C): The argument compares musicians to non-musicians, so it does not matter whether
two similarly trained musicians have roughly equal corpus callosa, only whether those musicians in
general have larger callosa than non-musicians.

Answer choice (D): The argument specifically stated that, on average, the corpus callosum of a musician
is larger than that of a non-musician, so the argument would not make the needless assumption that all
musicians have larger corpus callosa. Applying the Assumption Negation Technique, we would see that
the argument is unaffected by the assertion that “not all musicians have larger corpus collosa than any
non-musicians.”

Answer choice (E): By logically negating this answer choice, we get, “adult non-musicians did
participate in stimulating activities when they were children.” This negated version does nothing to
weaken the author’s argument, so we know this choice does not reflect an assumption required by the
argument.

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