LSAT 90 – Section 4 – Question 26

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Type Tags Answer
Curve Question
PT90 S4 Q26
Parallel flawed method of reasoning +PF
+Harder 148.293 +SubsectionMedium

This is a Parallel Flaw Method of Reasoning question.

The stimulus says that every Labrador retriever in my neighborhood is a well-behaved dog. Here we can kick the idea of dogs and my neighborhood up into the domain and say lab → well behaved. However, no pet would be well behaved if it were not trained. Dogs are a subset of pets, so you can kick the idea of pets into the superset and say /trained → /well behaved. The contrapositive is well behaved → trained. This allows us to hook up our conditions to get the following:

lab → well behaved → trained

We can connect the second claim about pets to a claim about dogs because if a rule pertains to all pets, then it must also pertain to all dogs since dogs are a subset of pets.

And here comes the conclusion. Thus it is training, not genetic makeup of the breed, that accounts for these Labrador retrievers’ good behavior. This is a causal claim with a positive and a negative component. The positive component is that training accounts for good behavior, and the negative component is that it is not the genetic makeup of the breed that accounts for good behavior. Note that “genetic makeup” refers to the fact that the dogs in question are genetically of the Labrador breed. So I would write:

lab → well behaved → trained
training —cause→ well behaved
not (lab* —cause→ well behaved)

The asterisk is to indicate that it is not exactly the fact that the dog is a Labrador, but a variant of this idea (genetic makeup of the dog) that does not cause good behavior.

This is a strange argument. The premise establishes that training is a requirement for being well behaved so it does seem like there's some causal power flowing from training to behavior. But how can we be sure that genetics has nothing to do with it? There's no support for that claim at all.

While it's good practice to think about why the argument is weak, this is a Parallel Flaw question so you don't really have to in order to get the question right. You can just do a formal mapping, like this:

▢ → ◯ → △
△ —cause→ ◯
not (* —cause→ ◯)

Correct Answer Choice (B) gives us this. Whenever it snows there are relatively more car crashes on the highways. Kick highways up into the domain. Within this domain, snow → more crashes.

Then (B) says yet in general, there would not be car crashes unless people were careless. Here, “in general” is the superset of the highways, and “unless” is group 3 negate sufficient, which means carelessness is a necessary condition for crashes (crashes → carelessness). All crashes, of course, includes the “more crashes” on snowy days, so:

snow → more crashes → carelessness

And (B) gives us the correct causal conclusion with the positive and the negative components. (B) says it is not icy roads, but carelessness, that causes car crashes when it snows. Notice how the icy roads are not exactly snow, but a version of it, similar to what we had for Labradors and genetic makeup.

carelessness —cause→ crashes
not (snow* —cause→ crashes)

Answer Choice (A) says all the students at Bryker School excel in their studies. Kick students up into the domain. The stimulus was talking about a subset of dogs, the Labrador retrievers. Here, we are talking about a subset of students, the ones at Bryker. So within this domain of students, Bryker → excel. However, students at Bryker School would not excel if they did not have good teachers (/good teachers → /excel). Notice this claim is not a more general claim and therefore already a bit off. But let's keep going and take the contrapositive, excel → good teachers, and chain it up:

Bryker → excel → good teachers

(A) lacks the domain shift we had with the pets, but I suppose this does not preclude it entirely. (A) is so far just a bit worse than (B), but what happens next really kills (A). (A) should have said:

good teachers —cause→ excel
not (*Bryker —cause→ excel)

In other words, it is the good teachers that produce (or some other causal verb) excellence, not the Bryker school or some asterisk version of it. But (A) instead says all schools should hire good teachers if they want their students to excel. This is a prescription. It's a policy recommendation. It's not a causal explanation. (A) maybe presumes a causal relationship, but then on the basis of that, makes a recommendation. In addition, notice that the conclusion in the stimulus is limited to the Labrador retrievers in the neighborhood. It doesn't attempt to draw a more generalized conclusion from the premises. Yet (A) does. (A) tries to draw a more generalized conclusion about all schools based on premises about the Bryker School.

Answer Choice (C) says every musician I know is a good dancer (musician → good dancer) and every mathematician I know is a bad dancer (mathematician → bad dancer). This already does not look good, but let’s keep going. There's an implicit premise that good dancers are not bad dancers. So, if musicians are good dancers, then they are not bad dancers, then they are not mathematicians.

musician → good dancer (→ /bad dancer) → /mathematician

Okay, so this at least kind of resembles our stimulus. What we need for (C) to work is to find this in the conclusion:

/mathematician —cause→ good dancer
not (*musician —cause→ good dancer)

In other words, not being a mathematician causes one to be a good dancer and being a musician* (like having a good sense of rhythm) doesn't. However, (C) gives us the opposite. It says it is a sense of rhythm, not the ability to count (mathematician*), that is responsible for good dancing.

Answer Choice (D) says all of the good cooks in my country use butter, not margarine, in their cooking. Let's kick “my country” into the domain. And within my country, good cook → butter and good cook → /margarine. Already, this is not going to work. You are not going to be able to hook up these two conditions by taking the contrapositive. (D) then concludes that if you want to be a good cook, you must use butter, not margarine.

We already know that (D) isn't right. But is (D) a good argument? Nope. It's terrible. Do good cooks in other countries also use butter and not margarine? And is using butter and not margarine what makes cooks good? The conclusion is a causal claim while the premise is merely an observational claim. I am sure that not too long ago, you could have made an observational claim that all of the best chefs in the world are men, and therefore, what... if you want to be a top chef, you must be a man?

Answer Choice (E) says all of the students in my algebra class received an A, even though none of them can solve word problems. The domain here is the algebra class, and within this domain we have student → A and student → /solve word problems. Like (D), we cannot hook up these two conditions by taking a contrapositive. But (E) has an additional premise. It says that no student who is unable to solve word problems has an adequate understanding of algebra (/word problems → /understanding). This is actually not bad because (E) now makes a general claim that applies beyond the algebra class and this claim chains up:

student → A
student → /word problems → /understanding

The second conditional chain resembles our stimulus, so we can ignore student → A. Now, what I need for (E) to work is the following causal conclusions:

/understanding —cause→ /word problems
not (*student —cause→ /word problems)

In English, it is the lack of understanding of algebra that's responsible (cause) for the inability to solve word problems, not the fact that one is a student*. The conclusion in (E), however, is that the students in my class received A's not because they did any good work. Where did “good work” even come from? And also, remember we are ignoring student → A since the parallel of this is not present in the stimulus.

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