Self-study
Support 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. ███ ███████████ ██ ███ ████ ██ ███████ ███████ ███ ████████████ ████████ ████ █████ █████████ ███ █████ ████████ ██████ ███ ███ ██ █████ ███ ████████ ██ █████ █████████████ ██████████ ███████ █████████ ████████████ ████ ██ ██████ ██ █ █████ ████ ██████ ███████ ████████ █████ ████████
Summary
The author concludes that musical training causes anatomic brain changes.
What makes the author think this?
Because the corpus callosum (part of a brain) of a musician is on average larger than that of a nonmusician. The differences are particularly significant when comparing adult musicians who began training around 7 years old to adult nonmusicians.
Notable Assumptions
The author assumes that the correlation between corpus callosum size and being a musician is due to musical training causing the corpus callosum to become larger. (This overlooks alternate explanations for the correlation. For example, perhaps people who start off with larger corpus callosums are more likely to show musical talent, which leads to a higher chance of receiving musical training.)
5.
Which one of the following ██ ██ ██████████ ██ █████ ███ ████████ ████████
a
The corpora callosa ██ ██████████ ██████ ████ ███████ █████████ ██ ███ ████ ██ ██ ██████ ████ █████ ██ ████████████ ██ ███ ████ ████
Necessary in order to eliminate an alternate explanation for the correlation between corpus callosum size and musical training. If (A) were not true, then the reason musicians tend to have larger corpus callosum could be that they started off with larger corpus callosum.
b
Musical training late ██ ████ ████ ███ █████ ████████ ███████ ██ ███ ██████
Not necessary, because the author’s conclusion doesn’t exclude the possibility of later musical training causing anatomic changes. Although the author thinks training at a young age may be more likely to lead to changes to the brain, the author’s open to later training also leading to such changes.
c
For any two █████████ █████ ████████ █████ ██████ ███ ███ ██ ██████ █████ ███████ ███████ ███ █████████████ ███ ████ █████
Not necessary, because the author’s argument is based on the average size of corpus callosum in musicians vs. nonmusicians. But individual musicians can have different-sized corpus callosum.
d
All musicians have ██████ ███████ ███████ ████ ██ ███ █████████████
Not necessary, because the author’s argument is based on the average size of corpus callosum in musicians vs. nonmusicians. Even if musicians have, on average, a larger corpus callosum, there can be many individual musicians with smaller corpus callosum than nonmusicians.
e
Adult nonmusicians did ███ ███████████ ██ ██████████ ████ ████ ████ ████████ ████ █████ ████ ██████████ ███ ██████ ██ ███ ██████ █████████
Not necessary, because even if adult nonmusicians have participated in activities that stimulated growth of corpus callosum, we still know that on average the corpus callosum of musicians is larger than that of nonmusicians. So music training could still play a causal role in making the corpus callosum larger, even if nonmusicians engaged in other activities that had a similar, though less pronounced, effect.