Hey dchan,
I've talked to a lot of students in your position, and one of the things that works best with SC is recognizing that it's often every bit as "logical reasoning" based as are CR or RC. So when I see you write something like this:
Yet I seem to be making no progress on SC even after learning all the potential errors.
I think what you need to do is not just *know* the errors, but think about them. You mentioned logical predication - those are a lot easier to spot based on the logic behind them than based on application/recognition of rules.
For example, a logical predation error could take the form of:
The primary goal of the oncological research department at Johns Hopkins is cancer.
Why is that wrong? It's illogical - the goal isn't "cancer" it's "treating cancer" or "finding a cure for cancer". You have to be reading that sentence for logic and meaning to really get that error, so it does require you to reason your way through it.
Parallelism is often the same kind of thing. To keep on a similar theme, here's an example of a parallelism error:
Despite the millions of dollars that have been spent on research, doctors maintain that treating Disease X remains much more difficult than Disease Y.
You can see this as a direct parallelism error, but it's also a logical/meaning error. "Disease Y" isn't "more difficult", it's "treating Disease Y" that's difficult.
Seeing these things logically can be extremely helpful as questions get harder. There's a great question out there that essentially hinges on the distinction between:
A) ...helps flies to distinguish their species from that of others
B) ...helps flies to distinguish their species from those of others
C) ...helps flies to distinguish their species from others
And most GMAT students immediately eliminate C, because they see the word "their" on one side of the comparison and think they need a possessive "That of" or "Those of" on the other.
But actually the answer here is C, because if you think it through logically, what is "others" but a pronoun for "species"? And you wouldn't say "the species of other species", so you don't need "that of" or "those of" here.
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My point with all this - to make that next leap in SC, try to go beyond categorizing or recognizing errors, and think about whey, logically, those errors are wrong. You can reason your way through a lot more SC questions than most people realize you can, and the tougher questions typically require you to do a lot of thinking. See if that helps...
