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# For most people, the left half of the brain controls

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Senior Manager
Joined: 31 Jul 2008
Posts: 280
For most people, the left half of the brain controls [#permalink]

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12 Nov 2008, 21:11
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Question Stats:

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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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Senior Manager
Joined: 04 Aug 2008
Posts: 369

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12 Nov 2008, 22:19
E

argument assumes that there is no other way to know where is the lingo center
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Manager
Joined: 08 Aug 2008
Posts: 228

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12 Nov 2008, 23:56
IMO E.

if it was possible to locate the language centres witout having to depend on occurence of stroke, the argument clearly falls apart....
Manager
Joined: 24 Sep 2008
Posts: 92

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13 Nov 2008, 00:16
(D)

If the language center is on the left, the stroke must cause some damage. If no damage then CR concludes that the language center is not even on the left side.
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Manager
Joined: 08 Aug 2008
Posts: 228

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13 Nov 2008, 01:24
the argument is about concluding the location of the centres...partial or total effect is outside the scope of the argument
Bidisha wrote:
(D)

If the language center is on the left, the stroke must cause some damage. If no damage then CR concludes that the language center is not even on the left side.
SVP
Joined: 17 Jun 2008
Posts: 1502

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13 Nov 2008, 01:41
IMO A. If my answer is correct, I will explain it.
Manager
Joined: 12 Jun 2008
Posts: 59

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13 Nov 2008, 01:44
D as well

E is too strong for me.
VP
Joined: 21 Jul 2006
Posts: 1485

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13 Nov 2008, 05:32
stallone wrote:
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.

I honestly feel that the answer should be B. The reason I don't like option E is that the argument is not focused on whether it's possible to determine where the language center is exactly located. The argument is a casual: The argument concludes that the damage of the language center causes impairment of linguistic capabilities. This means that the argument assumes that no other cause is possible to this effect of impairment. So, option B points out to this very fact that other causes indeed do not exist.
VP
Joined: 05 Jul 2008
Posts: 1368

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13 Nov 2008, 18:05
tarek99 wrote:
stallone wrote:
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.

I honestly feel that the answer should be B. The reason I don't like option E is that the argument is not focused on whether it's possible to determine where the language center is exactly located. The argument is a casual: The argument concludes that the damage of the language center causes impairment of linguistic capabilities. This means that the argument assumes that no other cause is possible to this effect of impairment. So, option B points out to this very fact that other causes indeed do not exist.

I disagree. Initially I picked B and started to do a negation test. It does not have any effect on the conclusion. Even though E is strong, it takes the conclusion apart. The conclusion is determining the location of LC based on stroke and its effect on L. If E were false, then we don't need to analyze stroke and its repercussions to tell whether a person has LC in Left or right brain. So E has to be true, even though impossible sounds a bit strong
Director
Joined: 30 Jun 2007
Posts: 765

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13 Nov 2008, 18:50
Conclusion: 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. [Irrelevant]

B. Impairment of linguistic capabilities does not occur in people who have not
suffered any damage to any language center of the brain. [Ok but has nothing to do with the conclusion]

C. Strokes tend to impair linguistic capabilities more severely than does any other
cause of damage to language centers in the brain. [Argument is not about comparison between strokes and others]

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. [Hold on]

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. [Irrelevant]

Intern
Joined: 28 Oct 2008
Posts: 47

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13 Nov 2008, 20:16
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.

My prephrase before reading the question stem is that the language center must be located in only one half. Too bad this wasn't an answer choice. But let's proceed to the answer choices...

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.
Eliminate:Scope. We can't assume anything about recovery. We're only interested in language and which part of the brain it comes from.
B. Impairment of linguistic capabilities does not occur in people who have not
suffered any damage to any language center of the brain.
Eliminate:Scope. This is the wrong group of people.We're talking about people who HAVE suffered from a stroke.
C. Strokes tend to impair linguistic capabilities more severely than does any other
cause of damage to language centers in the brain.
Eliminate: Too strong. "Tend" means more often than not. Moreover, this statement is comparing different degrees of damage from other causes as compared to a serious stroke.
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.
My choice. If a serious stroke occurs and the bleed in the brain does not affect any linguistic centers, the person is still utilizing his left brain. Therefore, the conclusion that the person has their linguistic center on the right half of the brain does not follow.
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.
Eliminate: Too strong. "Impossible?" Everything is possible, the impossible only takes longer.....har har har....But seriously, the scope has shifted to people who have not suffered damage to their brain. This statement is too broad.
VP
Joined: 18 May 2008
Posts: 1201

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13 Nov 2008, 23:24
I will go against the current and chose A.The conclusion says a person must be having language centre in the right half,if he got stroke in the left side w/t suffering any impairements. But wht if the language centre was in left half only & the damaged part recovered? thus there wnt be any impairement? Hence, wnt the argument fall apart? Any takers?

stallone wrote:
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.
Intern
Joined: 27 Sep 2008
Posts: 35

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13 Nov 2008, 23:49
D..again.!

What is the OA?
Manager
Joined: 26 Oct 2008
Posts: 108

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14 Nov 2008, 00:54
First attempt to post this explanation failed...

The answer is D. The conclusion of the argument is an if-then claim: If a person suffers a serious stroke on the left side AND his/her linguistic capabilities are not impaired, then all his/her language centres are on the right side. The only relevant evidence is the statement that if a language centre is damaged, then a person's linguistic capabilities will be impaired. The contrapositive of the evidence (which is logically exactly the same statement) is that if a person's linguistic capabilities are not impaired, then no language centres were damaged.

We can combine the contrapositive version of the evidence with the "if" part of the conclusion and produce the following: If a person suffers a serious stroke on the left side and his/her linguistic capabilities are not impaired, then no language centres were damaged. This is as far as the evidence gets us. In order to create the entire conclusion of the argument, we need to add one more if-then statement: If no language centres were damaged, then there are no language centres on the left side. This if-then statement is the missing assumption.

Now look at D, and notice that it is the contrapositive of that missing assumption -- which means that it IS the missing assumption, because a contrapositive and its "original" are logically the same statement.
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Kaplan Canada LSAT/GMAT/GRE teacher and tutor

Intern
Joined: 20 Sep 2008
Posts: 15

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14 Nov 2008, 07:22
Answer D.Since the statement assumes that if the stroke were to happen on the left side , the language centre is bound to be affected.

so the choice D correctly states that implied assumption.
Senior Manager
Joined: 31 Jul 2008
Posts: 280

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14 Nov 2008, 12:33
thanks for all ur replies .... the OA is D
VP
Joined: 21 Jul 2006
Posts: 1485

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15 Nov 2008, 20:40
but in option D, what does "at least one of them" refer to?
Senior Manager
Joined: 04 Aug 2008
Posts: 369

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15 Nov 2008, 22:40
this question is ridiculus 'at least one of them'
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Manager
Joined: 26 Oct 2008
Posts: 108

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15 Nov 2008, 23:20
I'm kind of old, and in my experience, the only stupid question is one that you didn't ask.

"at least one of them" means "at least one of the language centres". There is no other plural noun which "them" could refer to.
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Kaplan Canada LSAT/GMAT/GRE teacher and tutor

Senior Manager
Joined: 06 Apr 2008
Posts: 401

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16 Nov 2008, 04:23
IMO D)

If you remove the assumption that stroke does affect a language centre, then arguument fails.
Re: CR....   [#permalink] 16 Nov 2008, 04:23

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