The brains of identical twins are genetically identical.

[BTGmoderatorDC]

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 twins 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.


OA B

Source: Manhatta Prep

[deloitte247]

let's find the answer choice with the information that must be true in order for the argument in passage to be accurate. The passage conveyed a message that let us know that Schizophrenia is caused by damage to the physical structure of the brain.

Option A - Incorrect:
This answer choice goes too far in its assumption. According to the passage, only certain areas of the brain of a person suffering from schizophrenia are affected and not the whole brain. in addition, this option focuses on the effect on suffering from schizophrenia rather than the causes of schizophrenia. Hence, it is wrong.

Option B - Correct:
This answer choice is correct. The relative smallness of certain parts of the brains of schizophrenics is caused by damage to the physical structure of the brain, and not as a result of schizophrenia or of medications used in its treatment.

Option C - Incorrect:
This claim is off point, the comparison in the size of brains between people not suffering from schizophrenics is not relevant to the argument.

Option D - Incorrect:
This may be partially true in finding the effect of schizophrenia on identical twins who are both suffering from it. However, it is completely wrong when finding the causes of schizophrenia which is the main thrust of the given argument.

Option E - Incorrect:
This claim is off point and irrelevant to this passage.

[nischalp]

If we negate B

It implies that Disease caused the brain to shrink, breaking the conclusion.

General Tip- If A causes B, B does not cause A.