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’s 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 twines is no smaller, on average, than the brain of person who is not a twin.
(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


If the statements on which the conclusion above is based are all true, each of the following could be true EXCEPT:
(A) People who lack a genetic susceptibility for the disease will not develop schizophrenia.
(B) Medications can control most of the symptoms of schizophrenia in most patients but will never be able to cure it.
(C) The brains of schizophrenics share many of the characteristics found in those of people without the disorder.
(D) It will eventually be possible to determine whether or not someone will develop schizophrenia on the basis of genetic information alone.
(E) Brain abnormalities associated with schizophrenia are the result of childhood viral infections that inhibit the development of brain cells.
OA - D why not A[/spoiler]

sogmat wrote: OA - D why not A[/spoiler]

Let's say some people have Alpha in their genes, and some people don't. Some people who have Alpha will get schizophrenia and some won't. Those who do not have Alpha will never get it.

Now that is a theory, but whether you believe it or not doesn't matter, because given the information provided, it is possible. So A remains in.

As for D, we are told that twin brains are genetically identical, yet one twin may develop schizophrenia and the other may not. So we won't be able to predict anything based off of genetic information.

Could someone explain why B is the correct answer in the first question?

mikeCoolBoy wrote:Could someone explain why B is the correct answer in the first question?

The passage implies that a shrunken part of the brain is a part of the brain that has been damaged. The theory being presented states that schizophrenia is caused by damage to the brain. So damage comes FIRST, then schizo.

If the theory is true, then we have to assume that Schizo didn't come first and cause small brain, or that Schizo came first and the parts of the brain got small because of medication.

Thank you for the explanation.

You're welcome

please lemme know why B is not correct as it could also not be true coz it is never mentioned in the passage.
Also about the genetic information for the disease as mentioned in the answer choice D, it is not mentioned that it is possible or not that the disease will develop or not. I mean if D could never true, then on the similar basis B could also never be true as it is not mentioned in the passage and to answer must be true EXCEPT questions we need to refer the facts mentioned in the argument.
sogmat, could u please post the source for this question as well. so that i can practice these questions..

Experts, please elaborate this and help me out of this ambiguous situation.
thanks.

Hi Ketkoag,

Don't know if I qualify as an expert, but let me take a crack at it.

The second question asks which COULD be true. If something is not proved wrong by the passage, it COULD be true, even if the passage makes no mention of the subject.

D is proved wrong by the passage. We are given evidence that twins- who have identical genetic brains- can have one twin develop schizo and the other not. This proves that genetic information will not be able to predict whether one will develop schizo.

thanks a lot.....

I believe the correct answer should be B