mollyweasley wrote:
GMATNinja bb could you explain why choice D is incorrect?
The researchers conclude that they have found the anatomical cause of tone deafness: tone-deaf people have "many fewer fibers on the arcuate fasciculus" than do non-tone-deaf people. In fact, 90% of tone-deaf people don't seem to have a "superior branch of the arcuate fasciculus."
We're looking for a major flaw in the researcher's reasoning. Here's (D):
Quote:
D. Fibers in the arcuate fasciculus of the tone-deaf participants exhibited more activity than did those of the control group.
(D) gives us a bit more information about the nature of the difference between tone-deaf and non-tone-deaf people. Tone-deaf folks have "many" fewer fibers, but those fibers exhibit "more activity."
Notice that we don't know
how much more activity -- it could be that these fibers are just SLIGHTLY more active, meaning that "many fewer" fibers in tone-deaf people are still processing way less info than those in non-tone-deaf people. Additionally, (D) doesn't tell us exactly
where these more-active fibers are located. Perhaps the issue is that these people don't have a "superior branch," and increased activity in other fibers won't make up for this deficit.
Overall, (D) is perfectly compatible with the researchers' reasoning. There is still a notable anatomical difference between the two groups, and (D) doesn't give us a reason to doubt the researchers' argument.
Compare that with (B):
Quote:
B. An inability to produce sounds that match a particular tone induces fibers of the arcuate fasciculus to atrophy and die.
This tells us that the researchers are
way off. Instead of the difference in fibers causing tone deafness, tone-deafness causes the difference in fibers.
This really blows a hole in the researchers' reasoning. (D) is out, and (B) is the correct answer.
I hope that helps!