#22 - Scientists once believed that the oversized head, long

[Alex Bodaken]

1month2go,

Thanks for the question! This is an evaluate the argument question, for which we can use the Variance Test, which asks us to supply two opposite answers to the question proposed in the answer choice and see how they effect the argument; if one strengthens and one weakens it, then it is the correct answer choice. So for answer choice (B), which reads "At what stage in its life did the recently discovered dinosaur die?," our two polar opposite answers could be "at birth" and "in old age." Well, if the dinosaur died at birth, this weakens the argument (that T-Rex features were not dependent on size/weight) significantly, as it suggests that this evidence (on which the conclusion is based) of a new dinosaur is meaningless as it simply is a baby dinosaur and therefore can't be compared to a grown T-Rex. Alternatively, if this earlier dinosaur died in old age, it would be comparable to a grown T-Rex, which would make this evidence (and therefore this conclusion) stronger. Because the two polar opposite answers to this question weaken and strengthen the conclusion, this is the correct answer choice.

Cowboys1118,

Thanks for the correction - you are correct that the actual conclusion is that the the oversized head, long hind legs, and tiny forelimbs that characterized Tyrannosaurus rex did not develop in order to accommodate the great size and weight of this prehistoric predator.

Thanks and hope this helps!
Alex

[Adam Tyson]

That's correct, Cowboys! This is a classic "some people say ___, but they're wrong, and here's why" stimulus, the conclusion of which is the part that says "they are wrong".

Good catch! In this case, as you said, it wouldn't matter, but in another it might, so it is important to pay attention to those finer points. Well done!

[emilyjmyer]

I know there have been several explanations for why A is incorrect but I am still not understanding it. If the head was proportionate to the body of the t-rex but still had the same features wouldn't that tell us if the head was developed in order to accommodate the size of the t-rex?

Thanks,

Emily

[Rachael Wilkenfeld]

Hi Emily,

I know this probably won't help you much, as your test date has passed, but for anyone else, here's an explanation. Here, when the stimulus says that the specimen has the same characteristic features as the T-rex, we can relate that back to the characteristics described in the earlier part of the stimulus---the oversized head, short arms, and so on. We don't need to know that the ratio is exact to know that the basic idea is there.

On the other hand, knowing if the specimen was a full adult or juvenile would be relevant. Animals have different development and sizing as growing kids than as adults. Think about newborn babies. I think of them as bobble-heads, which is one of many reasons I don't recommend letting your LSAT instructor babysit your newborn. But seriously, they have these giant heads for their tiny tiny bodies. People don't keep that ratio as they are adults. Similarly, knowing about a baby new specimen wouldn't tell you as much about the adult form as an adult specimen would.

[mkloo11]

Hi! Sorry to reactivate this question, but I'd be very grateful if someone could help me figure out where I'm going wrong with this one. I now understand why B helps evaluate the argument, but I'm still having trouble ruling out D.

I'd originally used the variance test on B and D, and then selected D. My thinking was that the conclusion of the argument is that "this belief [that the T Rex's characteristics developed to accommodate it's size/weight ] must now be abandoned" on the basis of the new discovery.

I thought that the Variance Test showed that the species distinction was important. My thinking was, if the answer is "yes" -- the skeleton is a confirmed T Rex -- then its size is relevant to confirming or invalidating our long-held belief. So this strengthens the conclusion of the argument, that we should reconsider our previous theory in light of this new development. But if the answer is "no" -- the skeleton is known to be some other kind of dinosaur -- then it is not relevant to our thinking about the T Rex. In that case, this weakens the argument to abandon our previous theory on the basis of the new (not relevant) development.

So I guess my question is: Did I misunderstand what the true conclusion of this argument is? Is the conclusion "we should abandon our old theory in light of new evidence" (what I'd thought), or that "the T Rex's characteristics developed as they did for some reason other than to accommodate its size/weight?"

Thank you so much in advance!



But if the variance test supported that the speci because: If the answer is "yes" (

[Rachael Wilkenfeld]

Hi mkloo,

You did a lot of things right here, so don't get too frustrated by the difficulty here. Let's look closer at the argument before jumping into why answer choice (D) doesn't work.

The stimulus tells us that scientists thought that the characteristics of T-Rex (head, arms, and legs) were due to its large size and weight of the T-Rex. But then they found a skeleton that had the same characteristics but was a much smaller size and weight. The author concludes from this that the initial scientific theory must have been incorrect.

You were correct on the conclusion here, but your reasoning is off. It doesn't matter if the new skeleton is a relative of the T-Rex or not. Even if we answer the question no, it doesn't hurt the author's argument. The author argues that the characteristics of the T-Rex did not cause the size/weight of the T-Rex because the new skeleton gives us an example of the characteristics occurring without the large size and weight. The causal link is between the characteristics and the size/weight, not between the characteristics and the specific type of dinosaur.

Hope that helps!

[mkloo11]

Oh! Well that seems so obvious now. That helps a ton; thank you so much for the speedy help.

[CristinaCP]

I see why B is right. If the species died young, then what if it were just a fossil of a baby T.Rex? If it were a full-grown T. Rex, then the argument is somewhat strengthened. But similar to B, I think D also presents "What ifs" that would strengthen and weaken. So even after reading this thread, I can't understand why it's wrong.

I chose D because if the species of the discovered fossil were related to T. Rex, and we know it came earlier, then what if T.Rex descended from the earlier smaller dinosaur? If that were true, then the claim would be strengthened: the traits didn't develop as a result of large size, because maybe they first originated in a much smaller species.
If it weren’t related to T. Rex at all, then maybe the traits developed for independent reasons, which would in turn weaken the argument: the T. Rex could have developed its traits because of its large size, and the other fossilized dinosaur could have developed its traits for another reason.

I'm confused because I feel like you can use the same line of reasoning to say both B and D are correct: If you answer yes/no to each question, you can come up with "what ifs" that strengthen/weaken the argument.

What am I missing? Am I approaching these questions wrong?

[srusty]

Hi Cristina! So in this case, even if we assume answer choice (D) to be the best way to evaluate the argument, the consideration from answer choice (B) will still trump any conclusion we can make. Like you said, we could draw a thread from T. rex to earlier species to show that perhaps the traits developed just from heritage, not for a particular purpose. But would it still not matter to know the age of the earlier species when it died? Basically, the consideration put forth in answer choice (B) is kind of the “umbrella” under which answer choice (D) must be. It takes much less “what ifs” to understand how answer choice (B) evaluates the argument compared to answer choice (D). Hope this helps!

[willwants170]

During my PT, B and D stood out to me. Comparing D to B led to a train of thought. I had the correct answer explanation for B, just like the staff's explanation but using D, I thought what if this dinosaur was unrelated to the T. rex? Then, it being juvenile or geriatric would be useless to explain the characteristics of the T. rex. So I chose D, the next best answer. Turns out the answer was B, but doesn't B leave open the possibility that this fossil wasn't related to the T. rex and consequently make evaluating B useless? What's wrong with this thinking?