For most people, the left half of the brain controls linguistic capabilities, but some people have their language centers in the right half. When a language center of the brain is damaged, for example by a stroke, linguistic capabilities are impaired in some way. Therefore, people who have suffered a serious stroke on the left side of the brain without suffering any such impairment must have their language centers in the right half. Which of the following is an assumption on which the reasoning in the argument above depends? (A) No part of a person's brain that is damaged by a stroke ever recovers. (B) Impairment of linguistic capabilities does not occur in people who have not suffered any damage to any language center of the brain. (C) Strokes tend to impair linguistic capabilities more severely than does any other cause of damage to language centers in the brain. (D) If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages at least one of them. (E) It is impossible to determine which side of the brain contains a person's language centers if the person has not suffered damage to either side of the brain.

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For most people, the left half of the brain controls linguistic capabi

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Basshead

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08 Sep 2021, 12:22

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- Left or right half the brain controls linguistic capabilities
- When this is damaged --> linguistic capabilities impaired
- Conclusion: People who suffered a serious stroke on the left side of brain without suffering impairment must have their language centers in the right half.

Which of the following is an assumption on which the reasoning in the argument above depends?

A – Can we say that no part of a person’s brain that is damaged by a stroke ever recovers? Absolutely not. Be suspicious of strongly worded answers.

B – If A --> B, does Not B --> Not A? No. This is essentially what this statement is saying.

C. Out of scope. We are not interested in ‘any other cause of damage to language centers.’

D. This looks good. If we negate this choice, it says:

If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain will not damage them.

This completely shatters the conclusion.

E. Irrelevant to the conclusion.

Answer is D.

rrn98

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26 Apr 2022, 12:29

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For "(D) If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages at least one of them."

What does "at least one of them mean"? What is "them" referring to?

MartyTargetTestPrep

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26 Apr 2022, 14:41

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rrn98

"Them" refers to "language centers." So, "at least one of them" means "at least one of the language centers."

rrn98

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26 Apr 2022, 15:05

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Thank you so much MartyTargetTestPrep
I have an additional doubt: why is B wrong?

Quote:

(B) Impairment of linguistic capabilities does not occur in people who have not suffered any damage to any language center of the brain.

I'd think that it would help to understand that linguistic capabilities impairment in one side of the brain is caused by a stroke in said side of the brain. If impairment can happen due to other causes its effect wouldn't be quite clear right?

MartyTargetTestPrep

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27 Apr 2022, 11:30

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rrn98

Thank you so much MartyTargetTestPrep
I have an additional doubt: why is B wrong?

Quote:

(B) Impairment of linguistic capabilities does not occur in people who have not suffered any damage to any language center of the brain.

Notice that the underlying idea here is not that, IF there is impairment, THEN there must be damage.

The underlying idea is that, IF there is damage, THEN there is impairment.

After all, the author concludes, "people who have suffered a serious stroke on the left side of the brain without suffering any such impairment must have their language centers in the right half."

We can see that the author's underlying idea is that, if a person has NOT suffered impairment of linguistic capabilities, then there must not be damage to the person's language centers.

The author does not have to assume that there is no other way for such impairment to occur in order to arrive at this conclusion about a situation in which such impairment has not occurred.

muralis18

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07 May 2022, 23:39

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I wanted to know the reason behind option D to be correct.

Isn't it already stated in the passage that when the language barrier is damaged by stroke, linguistic capabilities are impaired -> "When a language center of the brain is damaged, for example by a stroke, linguistic capabilities are impaired in some way"

So stroke damages the language barrier to causes impairment.

And option D just restates the same -> stroke damages at least one of the language barriers.

Experts' opinions on this would be helpful, to fill any logic gaps that I'm missing.

Best.

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08 May 2022, 03:48

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muralis18

Let's look again at the two statements you quoted above.

Here's what the passage says:

When a language center of the brain is damaged, for example by a stroke, linguistic capabilities are impaired in some way.

So, IF damage to language center, THEN linguistic capabilities are impaired.

Here's what choice (D) says:

(D) If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages at least one of them.

So, IF language centers, THEN stroke damages them.

We can see that the two statements are actually quite different.

Now, let's consider the conclusion of the argument:

people who have suffered a serious stroke on the left side of the brain without suffering any such impairment must have their language centers in the right half.

So, IF stroke on left side + no impairment, THEN language centers on right side.

Notice that the author is assuming that stroke on left side = damage to language centers on the left side, which is basically what (D) says.

Raman109

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30 Nov 2023, 08:27

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Understanding the argument -
For most people, the left half of the brain controls linguistic capabilities, but some people have their language centers in the right half. - Fact.
When a language center of the brain is damaged, for example by a stroke, linguistic capabilities are impaired in some way. Fact
Therefore, people who have suffered a serious stroke on the left side of the brain without suffering any such impairment must have their language centers in the right half. - Conclusion

What if one suffers a stroke and it doesn't impact linguistic capabilities? Then, can we say that "they must have their language centers in the right half"? No, we can't. That is what option D highlights.

Option Elimination - We need to find a missing premise or a minimum condition that can make the conclusion work: "people (who have suffered a serious stroke on the left side of the brain without suffering any such impairment) must have their language centers in the right half.

(A) No part of a person's brain that is damaged by a stroke ever recovers. - "Recovery" is in no way linked to the scope at hand, which is finding a missing premise to make the conclusion work, which is "people (who blah blah..) have their language centers in the right half. Out of scope.

(B) Impairment of linguistic capabilities does not occur in people who have not suffered any damage to any language center of the brain. - People "who have not suffered any damage to any language center of the brain" are not in scope. We are talking here about people "who have suffered a serious stroke on the left side of the brain without suffering any such impairment." Distortion.

(C) Strokes tend to impair linguistic capabilities more severely than does any other cause of damage to language centers in the brain. "other damages" is out of scope.

(D) If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages at least one of them. - Yes. Negate the main clause "If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages "none" of them." or "If there are language centers on the left side of the brain, there could be a serious stroke affecting that side of the brain without damaging any of them." Then the conclusion "people (who blah blah..) have their language centers in the right half" shatters.

(E) It is impossible to determine which side of the brain contains a person's language centers if the person has not suffered damage to either side of the brain. - At best, it can be a weakener. Opposite of what we need.

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21 Jan 2026, 09:47

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Since the Option D is the restatement of the Fact from the STEM, I'm unable to comprehend why the option D is the right choice

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21 Jan 2026, 23:58

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Hi,

Let me help clarify:

The argument concludes that if someone had a serious stroke on the left side of the brain and no linguistic impairment, then their language centers must be in the right half.
For this conclusion to hold, it must be true that if a person had language centers on the left side, a serious left-side stroke would damage at least one of those centers.

Negation test: If a serious left-side stroke didn't damage any left-side language centers, then a person could have left-side language centers, suffer a left-side stroke, show no impairment, and yet still have language centers on the left. That would completely undermine the conclusion.

Hope this helps!

GMATFE2025

Since the Option D is the restatement of the Fact from the STEM, I'm unable to comprehend why the option D is the right choice