saad989 wrote:
Hey, I am a little confused here because the PowerScore Bible says that in the GMAT we are required to assume in causal relationships that the cause is the only cause and that there are no other causes that can create the particular effect. Thanks.
Well, that isn't strictly true. Smoking causes cancer, but there could still be other things that cause the disease, right?
I suspect what the book meant was that if two things are correlated and the passage concludes that one thing caused the other, it would weaken this conclusion if another potential cause is responsible for both.
For instance, if we know that there's a positive correlation between yard size and high SAT scores, we wouldn't necessarily conclude that big yards are causing kids to test at a higher level. It seems more likely that big yards are correlated with wealth, and wealthy people might be in better funded school districts or be more likely to hire tutors -- and
that's what causes both big yards and elevated test scores.
It's also true that if two things are correlated and we conclude that X causes Y, it would weaken that argument if we could show that Y was, in fact, causing X. To go back to our first example: there's a causal relationship between smoking and cancer, but cancer doesn't cause smoking (though tobacco companies used to argue this, oddly enough). When the evidence showed that causality ran the other way, it pretty much ruled out the tobacco companies' silly argument.
That's effectively what's going on in this argument. We see that there's a correlation between a tendency to manipulate and a tendency to become an addict. The conclusion is that the tendency to manipulate leads to addiction. (A) shows that it's the other way around. It's the addiction that leads to the tendency to manipulate, thus undermining the conclusion.
I hope that clears things up!