Logical Reasoning

PT106 · S3 · Q13 A recent study concludes that prehistoric

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

  • 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

Start practicing free

A recent study concludes that prehistoric birds, unlike modern birds, were cold-blooded.

Party 1

Prehistoric birds were cold-blooded (b/c growth rings in their body are thought to only occur in cold-blooded animals)

Party 2

Prehistoric birds were warm-blooded (b/c dense blood vessels in their bones suggest they were active creatures, and thus warm-blooded)

Evaluate

This isn't like a normal Paradox question, because it's not Background Fact vs. Surprising Claim, it's just Point of View 1 vs. Point of View 2.

So we won't try to frame our thinking in the normal way. We'll just recount the evidence in favor of each position so that we can better judge whether each answer choice seems go to with/against 1 or 2.

Goal

Maybe we'll support party 2 by saying answering party 1's concern and showing that warm blooded animals ALSO had these weird rings.

Maybe we'll support party 1 by answering party 2's objection, showing that cold-blooded animals sometimes had dense blood vessels in their bones and/or were active creatures.

Or there will just be a new fact that will incline us towards thinking that prehistoric birds were cold vs. warm blooded.

13.

Which one of the following, if true, would most help to resolve the dispute described above in favor of one party to it?

  1. Some modern warm-blooded species other

    Too Weak

    Answers with "some" are almost always wrong on Strengthen / Weaken / Paradox, since we're being asked which answer choice idea would have the most impact. This notion that "at least one modern warm-blooded species definitely descended from cold-blooded" helps Party 1 a bit, but it's just one data point, so not very compelling.

    4% picked this

  2. Having growth rings is not

    Too Weak

    This one is laughably weak. This says that "cold-blooded species have at least one physical trait besides growth rings". Cool. You mean physical traits like mouths, eyes, nose? How does that help us decide anything about birds? This one wouldn't help either Party.

    7% picked this

  3. Modern birds did not evolve

    Unclear Impact

    Since the argument between these two parties is about prehistoric birds, it's hard to figure out how finding out that modern birds are a completely separate thing from what they're arguing about has any effect on their conversation.

    6% picked this

  4. Dense blood vessels are not

    No Impact

    If this said that "some animals with dense blood vessels aren't warm-blooded", then it would help Party 1 a bit, by undermining Party 2's support. But it says "some warm-blooded species don't have dense blood vessels". That's irrelevant to the case being made for cold-blooded as well as to the case being made for warm-blooded.

    17% picked this

  5. Correct

    In some cold-blooded species the

    Why this is right

    This helps Party 1 a bit more than the other answers do. It still only says "at least one cold-blooded species has both growth rings and dense blood vessels". But this fact ends up being stronger than (A) or (D), since it reconciles Party 1's evidence for cold-blooded (growth rings) with Party 2's evidence against cold-blooded (dense blood vessels). It's a frustratingly weak correct answer on a weirdly structured question. We had no reason to be trying to support Party 1; that just happens to be what our best answer does. The trait of growth rings is thought to occur only in cold-blooded. The trait of dense blood vessels suggests active, which necessitates warm-blooded. So, growth rings is more tightly anchored to cold-blooded than dense blood vessels are to warm blooded. We end up strengthening Party 1, who already had a stronger case, by showing that Party 2's objection is totally compatible with the cold-blooded hypothesis.

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

    65% picked this

Continue the review in LSAT Lab

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

Save and practice this skill
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