In a study examining the neural pathway linking auditory perception

could someone please provide OE?

­B is right because the passage is clearly a causal passage. A causes B. In this case, tone deafness is caused by low concentration of the fibres. Option B clearly states that, there is a possibility where low concentration of fibres is caused by tone deafness. Which reverses the causal situation. Which is a major flaw in the argument. 

­The researchers concluded that fewer fibers in the arcuate fasciculus cause tone deafness.Answer choice B suggests that being tone-deaf causes the fibers to die off.

If B is true, the researchers have it backwards: tone deafness causes the fewer fibers, not the other way around. This means the researchers' conclusion about the cause of tone deafness is flawed.

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):

(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):

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!­

­The option that indicates a major flaw in the researchers' reasoning is: B. An inability to produce sounds that match a particular tone induces fibers of the arcuate fasciculus to atrophy and die.

This means that if being tone-deaf causes the fibers to weaken and die, the researchers' conclusion that the lack of fibers causes tone-deafness is flawed. It suggests that the problem with the fibers could be an effect of tone deafness, not the cause.­

B. this is a classic gmat answer. The stimulus says a Cause -> Effect.

The AC weakens this by reversing this relationship

I have done so many similar passages where we know A causes B, B causes A etc, but never knew a term - it's called a causal passage! Learned something new today

It is the classic cause-and-effect CR question. The argument fallaciously concludes that the lack of that particular neural pathway is what causes tone-deafness, however, it might be possible that tone-deafness itself causes that neural pathway to atrophy and eventually disappear. The argument correctly identifies the 2 elements of the cause and effect (the neural pathway and tone-deafness) but incorrectly identifies the relationship between them. Ans B