Maybe you're so well conditioned to say the argument core as your mantra, it's easier to see correct strengthen questions (since they will often reinforce that core move and call back to the same thoughts).
With Weaken, I'm always prephrasing
"Given that [the premise] is true,
How can we argue for [the anti-conclusion]?"
When you see the author's conclusion, think about THAT claim being the verdict that the author is trying to get the jury to believe. Meanwhile, you're the lawyer for the Anti-conclusion. You're trying to get the jury to believe that the author's conclusion is wrong.
By assigning myself the Opposing Counsel mindset, I react better to answers:
- Some answers will sound like evidence for the Anti-Conclusion, so I'll think, "hey that helps MY case!"
- Some answers will cheapen the trustworthiness or relevance of the Evidence the author has brought forward. So I'll think, "hey that hurts HIS case!"
- Some answers just sound like Opposing Counsel helping to raise doubt in the jury's mind. "yes, the bloody glove at the scene of the crime has the defendant's DNA on it. But isn't it possible that the DNA got on the glove before someone ELSE took the gloves and committed the murder?"
One of the most important patterns on the test (and Weaken question in particular) is recognizing when the Author's conclusion is really her Explanation for or Interpretation of some interesting fact.
f.e. "the average age of this city went from 55 to 58. There must have been more old people who moved in."
"Sales were 15% higher this month than last. Apparently, that new sales girl Kelly is crushing it."
"People who nap a lot are more likely to have insomnia. So it seems that napping leads to insomnia."
As soon as you see these types of arguments, you need to remind yourself of the two available pressure points:
1. Is there some OTHER way to explain/interpret the Evidence?
2. Is the author's explanation/interpretation PLAUSIBLE?
Strengthen questions frequently add to the plausibility of the author's explanation, and tricky correct answers RULE OUT an alternative explanation.
Weaken correct answers USUALLY provide an alternate explanation.
So your prephrase needs to prioritize #1, while keeping an eye for #2.
"How ELSE could an average age shift from 55 to 58?"
"Why ELSE could sales be 15% higher this month?"
"How ELSE can we interpret the correlation between napping and insomnia?"
Try some more Weaken questions with both of those tools front of mind:
1. Always articulate the Anti-Conclusion. Pretend to be that lawyer. Think of something you would want to say in court to move the jury in your direction or at least to diminish the case the author was trying to make.
2. Look out for conclusions that explain/interpret the evidence. If you don't prephrase that we're (probably) looking for a DIFFERENT way to explain the evidence, you'll be hunting for the wrong thing.