Logical ReasoningDifficulty: Hard

PT155 S4 Q18 Explanation

Certain changes in North American

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsWeaken

Keep going in LSAT Lab

  • Save & drill this skill build targeted practice sets from questions like this one

  • Video walkthroughs watch every question solved step by step

  • 81 official LSATs as questions, timed sections & full-length tests

Full official LSAT questions are available through LawHub. This page provides LSAT Lab's explanation, strategy, and review tools without republishing the full official question.

Stimulus

Certain changes in North American residential architecture after World War II are attributable mainly to the increased availability and affordability of air-conditioning. Soon after World War II, many builders found that air-conditioned houses lacking the high ceilings cool during extreme heat generally sold well.

What this question is testing

Weaken

Your task

Find the choice that makes the argument's conclusion less likely to be true.

Common trap

Answers that look negative but attack a claim the argument never relied on.

Winning move

Find the assumption the argument depends on, then pick the choice that undermines it.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
18.

Which one of the following, if true, most seriously weakens

Answer choices

  1. No Impact3% picked this

    High ceilings and thick walls enable houses to withstand many types of severe weather that are

    This tells us a timeless truth about high ceilings and thick walls. Since we're trying to assess a change that happened after WWII, the answer will probably deal with that time frame specifically. This detail about high ceilings and thick walls doesn't help us assess whether architecture moved away from this style because of A/C or some other reason.

  2. No Impact5% picked this

    Thin-walled, low-ceilinged houses are more costly to heat in winter than

    Again, like (A), this answer doesn't say anything about the specific time period we're investigating. This answer essentially leads us to think that thick walls and high ceilings are better in the hot of summer and in the cold of winter. So why did we move away from that? Not sure. This answer doesn't help solve that mystery.

  3. Correct61% picked this

    Houses with low ceilings and thin walls were prevalent in North America even where there was no

    Why this is right

    Well, I am pretty opposed to this question overall, so take this explanation with a grain of salt. This answer is trying to take the form of a (No Cause, Effect) plausibility weakener. When it uses the past tense "were", we're apparently supposed to assume that it's talking about the period right after WWII. i.e., "Hey author, if A/C was really the cause of moving towards lower ceilings and thinner walls, then how do you explain that these houses were prevalent even where there was no demand for A/C?" (The author could simply say, "I just said they were the main cause. There were lower ceilings and thinner walls in areas w/o demand for A/C for some of those secondary reasons, such as they're cheaper to build and you can build more floors with lower ceilings.") This answer would only have the power the test writers are wanting it to have if it had said "houses with low ceilings and thin walls were just as prevalent where there's no demand for A/C". Or it would be better if it said, "Houses with low ceilings and thin walls were prevalent in new constructions after WWII even where there was no demand for A/C." Otherwise, it's really an answer with no impact. "Prevalent" just means "common / not rare". I'm sure that many styles of house are prevalent in all places. That doesn't mean they're desired or newly constructed or trending. Houses with stucco painted ceilings are very prevalent right now (because that was a fad in the 70s), but modern builders don't make new homes in that style. So even though modern builders have made a certain change in terms of how they paint ceilings in residential architecture, that old style is still prevalent in existing houses. Sigh, oh well. We can't fight city hall. I don't know why they think this answer is better than (E), which introduces an alternate explanation. But they think that this answer calls into question the plausibility of the author's explanation by saying that the observed effect (thinner walls / lower ceilings) was present even in areas not affected by the supposed cause (demand for A/C).

    Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

  4. No Impact13% picked this

    Thin walls allow cool, air-conditioned air to escape more readily from houses than

    One might interpret this as weakening in the sense of, "This story makes no sense! You're saying they switched to thin walls because of A/C. Thin walls actually let air-conditioned air escape more easily!" But we already knew that. We know that high ceilings and thick walls are traditionally how houses insulated cold air during the hot months, so we already know that any house with A/C and lacking thick walls is going to be letting more air escape than a thick-walled, more insulated house would. The gist was that we were able to switch to thinner walls because the A/C was making it so that we didn't need to rely on thick walls to stay cool.

  5. Unclear Impact18% picked this

    Soon after World War II, new thermal-insulating technology was widely applied

    I would have picked this answer, as it suggests an alternate explanation for why residential architecture changed soon after WWII (you don't need high ceilings and thick walls to keep the inside cool during hot months if you most houses now have new insulating technology). I don't really know how to tell you why it's wrong. The best I can come up with is that LSAC thinks that because the author said "certain changes are attributable mainly to the increased usage of A/C" that we're not really weakening the argument to pose an additional reason why builders made the switch. Or it's possible that LSAC thinks of "thermal-insulation" technology as something that could be a solution for keeping homes warm but not a solution for keeping homes cool. (the problem with that is that anyone who lives in a hot desert climate knows that you open the doors and windows at night to let the cool night air in, and then you try to keep that cool air in your house throughout the hot day by keeping those doors and windows shut. Thermal insulation would seemingly help you to "protect" the cold air you let in at night, but perhaps that's too weird of an example for LSAC and they thought this answer would only provide a solution for heating homes, not cooling them).

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free