Critical Reasoning

The brains of identical twins are genetically identical. When only one of a pair of identical twins is a schizophrenic, certain areas of the affected twin"Ÿs brain are smaller than corresponding areas in the brain of the unaffected twin. No such differences are found when neither twin is schizophrenic. Therefore, this discovery provides definitive evidence that schizophrenia is caused by damage to the physical structure of the brain.

Which one of the following is an assumption required by the argument?

(A) The brain of person suffering from schizophrenia is smaller than the brain of anyone not suffering from schizophrenia
(B) The relative smallness of certain parts of the brains of schizophrenics is not the result of schizophrenia or of medications used in its treatment.
(C) The brain of a person with an identical twin is no smaller, on average, than the brain of person who is not twines.
(D) When a pair of identical twins both suffer from schizophrenia, their brains are the same size
(E) People who have an identical twin are no more likely to suffer from schizophrenia than those who do not.

I don't know it is drowsiness or toughness of these questions. I marked another one wrong, now it is 2 out of 6 wrong.
Conclusion: discovery provides definitive evidence that schizophrenia is caused by damage to the physical structure of the brain.
So i feel that our assumption should be something that assume that brain is not damaged by something else...but physical damage. so confusing...Expert help required.

The ans shuld be B...

IMO B.

Here is my reasoning.

Evidence:

The brains of identical twins are genetically identical.
When only one of a pair of identical twins is a schizophrenic, certain areas of the affected twin‟s brain are smaller than corresponding areas in the brain of the unaffected twin.
No such differences are found when neither twin is schizophrenic.

Conclusion

this discovery provides definitive evidence that schizophrenia is caused by damage to the physical structure of the brain

Now Since this is an assumption question.Find the logical gap in reasoning.

The argument states that that among twins "if one has schizophrenia,then this twins brains' certain parts are smaller than other twins'. But if none of them suffer from this disease, then their brains are of identical size.

The evidence is of correlation.But the conclusion is of causation

" damage to physical structure (smaller size of the brain) -> schizophrenia".

The argument,for it's conclusion to be valid,must not assume the opposite,i.e

"schizophrenia-> smaller size of brain).

The argument uses the term damage to physical structure to convey the meaning "smaller size of the brain".

Hence my choice B

A) anyone-? The argument isn't talking about anyone.The argument just mentions about two twins.

C) The question is about causation and not about comparison.Irrelevant.

D) We don't even know that for sure because the argument does not mention it. If you negate this statement ,you can still draw the conclusion.

E) Again causation vs comparison.We are not comparing people with identical twins with those without identical twins.

What is the OA?

OA is B.Thanks Rishab for nice explanation.

rishab1988 wrote:IMO B.

Here is my reasoning.

Evidence:

The brains of identical twins are genetically identical.
When only one of a pair of identical twins is a schizophrenic, certain areas of the affected twin‟s brain are smaller than corresponding areas in the brain of the unaffected twin.
No such differences are found when neither twin is schizophrenic.

Conclusion

this discovery provides definitive evidence that schizophrenia is caused by damage to the physical structure of the brain

Now Since this is an assumption question.Find the logical gap in reasoning.

The argument states that that among twins "if one has schizophrenia,then this twins brains' certain parts are smaller than other twins'. But if none of them suffer from this disease, then their brains are of identical size.

The evidence is of correlation.But the conclusion is of causation

" damage to physical structure (smaller size of the brain) -> schizophrenia".

The argument,for it's conclusion to be valid,must not assume the opposite,i.e

"schizophrenia-> smaller size of brain).

The argument uses the term damage to physical structure to convey the meaning "smaller size of the brain".

Hence my choice B

A) anyone-? The argument isn't talking about anyone.The argument just mentions about two twins.

C) The question is about causation and not about comparison.Irrelevant.

D) We don't even know that for sure because the argument does not mention it. If you negate this statement ,you can still draw the conclusion.

E) Again causation vs comparison.We are not comparing people with identical twins with those without identical twins.

What is the OA?

Dear Rishab,

Don't you think that use of medications in option B makes it OOS...

Best-
Amit

Amit,
>>Don't you think that use of medications in option B makes it OOS
In causation question, Strengthening and assumption questions works the same way. So, we have to do either of the five stuff.

(A) Refute an alternative cause.
(B) Show that whenever cause occurs, result occurs.
(C) Shot that whenever cause doesn't occur, result doesn't occur.
(D) Eliminate any possibility that stated relationship is reversed.
(E) Show that data used to make causal statement is accurate.


So, here we just need to refute any alternative cause. It can be anything (be it medications, or reversal process).

I hope am clear.

loving.achin wrote:Amit,
>>Don't you think that use of medications in option B makes it OOS
In causation question, Strengthening and assumption questions works the same way. So, we have to do either of the five stuff.

(A) Refute an alternative cause.
(B) Show that whenever cause occurs, result occurs.
(C) Shot that whenever cause doesn't occur, result doesn't occur.
(D) Eliminate any possibility that stated relationship is reversed.
(E) Show that data used to make causal statement is accurate.


So, here we just need to refute any alternative cause. It can be anything (be it medications, or reversal process).

I hope am clear.

Dear Achin,

makes sense!..so this is a case of reverse causation...Right?

Best-
Amit

Mix of A and D.

Mix of A and D.

loving.achin wrote:Mix of A and D.

Cool...

Cheers