Q23 - The brains of identical twins are genetically

by **WaltGrace1983** Sat Dec 13, 2014 5:32 pm

This is a very typically correlation/causation question.

Brains of identical twins are generally identical
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When one twin is schizo, certain areas are relatively smaller than unaffected twin
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Damage to physical structure of the brain causes schizo

The problem with this is that how do we know the logic flows in one particular way, so to speak? How do we know that it is brain damage that causes schizophrenia? Couldn't it be that schizophrenia causes the brain damage (a more likely possibility, in my opinion)? Or perhaps it is all just one big coincidence and people who have schizophrenia just so happen to have brain damage.

(A) "Anyone" is very strong. We are just comparing two twins here, nothing else.

(C) Same as (A). We are only caring about the relative sizes of twins' brains. It doesn't matter if the twins' brains are bigger/smaller/same size as non-twins' brains.

(D) Not necessary. They don't absolutely have to be the same size. Plus, this still wouldn't give us reason to believe that A causes B.

(E) Don't care about the relative likelihood of suffering from schizophrenia! We want to know something about causation!

(B) is correct. If we said that the smallness IS the result of the schizophrenia itself, this would demolish the logical flow of the argument.