When parents and grandparents tell personal and family histories to th

Thanks, AlexTheTrainer for replying
But I think if B is negated, then it should be "in relating family histories to their children and grandchildren, people are NOTonly likely to suppress incidents that they feel are discreditable, or incidents that are particularly painful to recall".
Now, this choice is debilitating the argument's conclusion. Because people will not hide any painful experiences, the family "history" will be accurate and not likely to become distorted.
Now after negating choice B, the argument is weakened. Hence this choice can be considered correct?

Your negation - “people are not only likely to suppress (discreditable) incidents” is NOT equivalent to “people likely do not suppress (discreditable) incidents”.

Negation doesn’t mean inserting “not” wherever one chooses - it has to make sense grammatically. Your negation “not only” would somehow need to include a “but (also)” in order to make sense.

Negating “only” means including other possibilities, rather than merely placing a “not” in front of it. Does that make sense?

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Thank you AlexTheTrainer for clearing my doubt. Yes, it does make sense.

Thanks for the reply. I was a bit concerned that I was too harsh in my reply. But this stuff is so complex that couching replies in mild language just isn’t effective.

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Answer B is not actually stated in the passage. The passage mentions two situations when parents or grandparents might distort their family history. The passage does not say that those are the only situations when that happens. But the argument still 'works' whether these are the only two situations or not -- if parents distort happy memories too, then the conclusion is actually even more true. So B is not an assumption.

I dislike the 'negation test', and the discussion in this thread illustrates why it can be problematic. If you don't insert the "not" in the right place, you won't be applying the test correctly, and then won't be able to correctly evaluate whether an answer choice is an assumption. You also need to think about the opposite of what each answer choice says, which is potentially confusing. The negation test works, but there's no need to use it, if you understand what an assumption is. Here, the argument says, roughly, "When parents tell family stories to children, parents lie. So children don't get an accurate picture of their family history." That argument only makes sense if children get their family history from their parents, so that's an assumption here, and E is correct.

Absolutely agree that B does not restate evidence from within the passage. In fact, answer choices will never simply repeat the evidence. They might look like they do, but they don’t.

But regarding the negation test. The assertion that some answers are difficult to negate and that the negation test is not always effective is absolutely correct. BUT:

Logicians (philosophers specializing in logic) use the idea of negation when defining an “assumption”. An assumption is something required in order for the conclusion to be true. That is, an assumption is necessary, but not sufficient, to create a valid argument. But what exactly does this mean?

Logicians will answer this question by pointing out that something necessary for an argument, when negated, will create a permanently invalid argument. And this does NOT mean that negating an assumption will “kill the argument”, that is no such idea exists in logic.

The point: negation is not a trick made up by GMAT prep folks. It’s a very real thing.

When it comes to assumptions, deductive reasoning is involved. Deductive reasoning means evaluating an argument based only on whether its valid or invalid and sound or unsound. The latter (soundness) goes to the truth of the evidence/premises, so is irrelevant for the purposes of the GMAT (evidence/premises are assumed to be true).

So on the GMAT, deductively reasoned arguments (such as those found in assumption questions) are considered only as valid (evidence leading to a conclusion that must be true) or invalid (evidence leading to a conclusion that does not have to be true). Negating the assumption of the argument generates a permanently invalid argument. Negation doesn’t kill the argument, just invalidates it.

By the way, the above is a good reason to avoid LSAT LR Assumption questions, because about half of them do not ask for an assumption that is required, but for an assumption that is sufficient to prove the conclusion to be true. This “Sufficient Assumption” question type is only found on the LSAT and is actually misnamed (all because the World’s Largest Prep Company refused to recognize its existence until about 15 years ago - long story). Regardless, the negation test doesn’t work for these question types.

In logic academic circles, there’s no such thing as a “Sufficient Assumption”. To many students, they look the same as Gmat assumption questions, but they will not use adjectives for “necessary” (requires, depends, etc.) in the question stem.

Fun times…

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Yes, I did my undergrad thesis in mathematical logic, so I understand how to formalize these things. As I said in my post, the negation test works, when applied correctly. If test takers had no difficulty applying it correctly, and if it was fast to use, it would be a great test. But I've seen many test takers, high-level test takers at that, who have difficulties applying the test, which is why I have reservations about it. It works, and anyone who likes it should use it if they're getting good answers with it, but it's not the only approach one can take.

Absolutely, no question about it.

I feel like a lot of prep folks imply that the negation test is like a magic trick that will suddenly make all assumption questions easy. But since it’s not easy, students get easily frustrated and give up on it.

Are you currently studying for the test? If so, then based on your background, I got something for you about these assumption questions that I think you can handle. It’s extremely subtle, which is why I tend not to write about it. But again, someone with your background should be able to understand what I’m trying to say.

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Ha, no, I've been teaching high-level GMAT math for more than a decade. I'm definitely interested in subtle logic issues, so do feel free to post here or pm me if there's something you'd like to share or discuss.

No! No! AlexTheTrainer you were not harsh in your reply. I am glad that replied and tried to solve the error in my negation technique.