[LSAT Dan]

I want to take a look at some specific question types over the course of a number of posts/articles. Longer, more complicated ones may be put up on the site as articles; shorter or simpler ones (like this one), I’ll probably just make forum posts. I’m starting with Strengthen/Weaken questions, because in my opinion, they’re the easiest of the common question types. In this post, I’m going to talk about three very common ways in which most S/W questions resolve. When you understand the underlying structure of various questions, the actual subject matter becomes relatively unimportant, even when it’s complex or convoluted.

First, let me state something that seems to be anathema to a number of test prep teachers and authors. It’s true that there’s a difference between strengthening or weakening the *conclusion* and strengthening or weakening the *argument*. HOWEVER (here comes the somewhat controversial part), the vast majority of the time, it just doesn’t matter. On a strengthen question, the right answer is the one that makes the conclusion more likely to be true, and on a weaken question, the right answer is the one that makes the conclusion less likely to be true. More than 95% of the time, it’s that straightforward. You could take every LSAT exam for two years and not come across a question where the difference between strengthening the argument and strengthening the conclusion matters at all. If anyone doesn’t know the difference between the two, and cares, let me know in a reply, and I’ll explain it, but I’m not going to do it here.

OK, so the right answer makes the conclusion more or less (strengthen or weaken, respectively) likely to be true. Very often, that will happen in one of three specific ways. I’m going to note them, briefly explain them, and reference actual past LSAT questions that illustrate them.

First, and probably the most common – on a weaken question, the right answer will often provide an explanation for something, and on a strengthen question, the right answer will eliminate an alternate explanation. What’s being explained? Something in the passage. The conclusion of the passage will be one possible explanation for an occurrence in the passage. Think of it like a criminal defense case. Let’s say you’re defending someone who is accused of a crime, and your client’s fingerprints are found at the scene. The prosecutor says that your client is guilty, and the fingerprints are evidence supporting the prosecutor. But let’s say your client was a cable TV installer, and was in the house (legitimately) a week before the crime. The prosecutor’s explanation for the fingerprints is that your client is guilty, but you have an alternate explanation for the fingerprints, and that weakens the case against your client. It doesn’t PROVE that your client is innocent; he could have gone back and robbed the house the next day. But it makes the (prosecutor’s) conclusion less likely to be true. If the jurors were 80% sure your client was guilty after hearing the prosecutor, now they’re only 60% sure.

Check out Preptest 63 (June 2011), Section 1, Question 2, about Jocko the chimp. Jocko gets a bunch of bananas and makes a bunch of noise; the other chimps come steal his bananas. The next day, he gets a banana, and he keeps his mouth shut. Conclusion: He was quiet to protect his food. The conclusion in this passage’s structure is an explanation for an occurrence – Jocko’s failure to make noise. We should look for an answer that provides a different explanation for his silence, and sure enough, one of the answers gives us one: Chimps only make noise when they get a whole bunch of food (like Jocko did the first time). That’s another possible reason for his silence, so the original conclusion, although it MIGHT be right, is now less likely to be true. That’s what we’re looking for.

Here’s a different type of answer for a S/W question with a different structure: The cause/effect argument. When it comes to strengthen/weaken questions, think of a cause/effect argument like a little 2×2 grid – horizontally, we have the cause, which can be present or absent; vertically, we have the effect, which can be present or absent. The intersection of these two factors gives us four boxes. I’m going to try to draw what I mean here, but I’m not sure if the formatting will hold up. But here’s the gist: If the (purported) cause and the effect are BOTH present or BOTH absent, that strengthens the argument; if either the (purported) cause or the effect is present when the other one is absent, that weakens the argument. Here’s that grid (hopefully):

CAUSE –> YES NO

EFFECT (YES) strengthens weakens

EFFECT (NO) weakens strengthens

Let’s give it some context: Let’s say on a particular island, people (on the whole) drink five times as much lemonade as people anywhere else in the world. And let’s say that on this island, the cancer rate is twice as high as it is elsewhere. So I conclude that lemonade causes cancer, and I slap together a group to test my theory. It would strengthen my argument if I had a group that consisted of a lot of lemonade drinkers who had cancer, OR if I had a group of NON-lemonade drinkers who DIDN’T have cancer. It would *hurt* my argument if I found a bunch of cancer-free lemonade drinkers, or if I found a bunch of cancer victims who don’t drink lemonade.

Cause without effect, or effect without cause = WEAKENS.
Cause & effect; OR no cause & no effect = STRENGTHENS.

Let’s use this lens to view one of the reputedly most difficult LR questions in LSAT history: Preptest 45, Section 1, Question 12, aka “the dioxin question.” If you do a Google search for hardest LR questions, you’ll find this one on a lot of lists, but should it be? According to an online Powerscore article, it took the LSAC themselves almost two pages to explain this question! Wow…I think I can do it a little bit more concisely (and simply) than that.

Notice, btw, that I don’t reproduce questions in my posts. That’s because they’re copyrighted. So if you can find a copy of Preptest 45, do it. Or you may find the question online, posted by someone less concerned about intellectual property rights (and getting sued) than I am.

One thing that makes this question awkward is that it’s a double negative – we’re trying to WEAKEN the argument that dioxin is NOT the cause of the abnormalities. Let’s just ignore that for now and reconstrue the question so it’s easier to follow: Does dioxin cause the abnormalities?

Let’s look at (C), since it’s the correct answer. We know that dioxin is released into the water daily, and we know that the fish have the abnormalities. But the fish recover quickly, and dioxin breaks down slowly, which suggests that it’s not the cause. Another way of looking at that is to say that we have the purported cause still present (dioxin breaks down slowly), and we don’t have the effect (the fish recover quickly). That’s the passage. But now let’s get back to (C).
(C) says that the river currents carry the dioxin away in a few hours. If that’s true, then not only do we have cause + effect (dioxin gets dumped; fish get sick), but (C) gives us the pairing of no cause + no effect (the dioxin washes away; the first get better). No cause + no effect STRENGTHENS the causal relationship. In other words, (C) makes it more likely that dioxin is the cause. To untangle the double negative, that’s the same as saying that it’s LESS likely that dioxin ISN’T the cause. So it’s a good answer.

The passage told us the fish recover; (C) is telling us that while the fish are recovering, the dioxin has moved on down the river, away from their first. So yeah, it was probably the dioxin that was the problem. The passage’s author who was saying that dioxin ISN’T the cause is more likely to be wrong, once we assume (C) to be true.

Finally, when a strengthen or weaken question involves a passage in which the argument is based on an analogy, the right answer will almost always pertain to the strength of the analogy. On a strengthen question, the right answer will give you a reason to think that the things being compared are similar in some key respect, and in a weaken question, the right answer will give you a reason to think that the things being compared are DISsimilar in some key respect – in other words, it’s “apples and oranges.” Preptest 30 (December 1999) gives us a great example of each in close proximity in Section 2.

The strengthen question is question 3, about peat harvesting. It’s an argument by analogy: What’s true in one situation (peat harvesting doesn’t pollute water in Ireland) is true in another (therefore, it won’t pollute water here). On a strengthen question, we should expect an answer that tells us that there’s a key similarity between the two situations: (B) is correct – the ecologies of the two countries are virtually identical. Notice how the wrong answers don’t even involve the strength of the comparison.

Fast forward to question 8, a weaken question also based on an analogy: What’s true about one situation (New farms should not be banned just because they don’t provide much of the nation’s total food supply) is true of another situation (New oil wells should not be banned just because they wouldn’t provide much of the nation’s total oil supply). What weakens an argument by analogy? An answer choice that tells us that the situations are different in a relevant respect: Unlike oil drilling, farms don’t involve a risk.

Notice that this question is harder, because other answer choices (such as (C) and (D) point out differences between the two situations. So how do we know that (A) is aimed at the RELEVANT difference? Because of the passage itself – (A) focuses on risk, and the opponent’s argument specifically mentions risk as a reason to oppose the drilling.

Compare Preptest 62, Section 4, Question 14 – an argument by analogy between privatizing the telecommunications industry and privatizing national parks. The right answer is (E); the two things are different with respect to the amount of competition that the privatization would bring. Other answer choices distinguish between national parks and telecommunications, but COMPETITION is the relevant distinction, because competition is specifically mentioned by the politician as the reason privatization was beneficial to telecommunications customers. When you understand the structure, the subject material doesn’t matter: 62-4-14, for all intents and purposes, IS 30-2-8.

If you haven’t done so, and you have access to them, I strongly urge you to read through all of the full text of the passages and the answer choices in these example questions. They were carefully chosen to illustrate patterns that recur again and again on the LSAT. I hope this helps some of you. Good luck to all, and please feel free to ask for any clarification.

-DFO

[Anonymous]

So basically cause and effect arguments for the majority of the time result in these 4 categories?

Cause without effect, or effect without cause = WEAKENS.
Cause & effect; OR no cause & no effect = STRENGTHENS

[LSAT Dan]

I’d say that when (on a strengthen or weaken question) the passage gives you a cause/effect argument, then yes, most of the time, the right answer will give you something that either pairs cause & effect (or the lack of both) on a strengthen question, or gives you one without the other, on a weaken question.