LR Question 18 Explanation
QUESTION TEXT: For several centuries there have been hairless dogs…
QUESTION TYPE: Necessary Assumption
CONCLUSION: The hairless dogs must have been transported between Western Mexico and coastal Peru by boat.
REASONING: It would have been hard to travel by land.
ANALYSIS: This argument makes a classic LSAT flaw: a false comparison. The author told us overland travel would be hard. But they told us nothing about boat travel. Maybe boat travel was equally hard. So the author is assuming that boat travel was easier.
___________
- What if hairless dogs were found in Central Africa or Mongolia (i.e. where they couldn’t reach Mexico/Peru). How would that affect the argument?
Negation: There are some hairless dogs in a remote region that had no contact with Mexico or Peru several centuries ago. - “Most” is a lousy answer on necessary assumption questions. When you negate it, it goes from 50.00001% to 50%. That has zero impact unless you’re talking about a vote.
Also, this answer doesn’t say the boat trade to Mexico came from Peru.
Negation: Merely half of all trade that came into Western Mexico came by boat. - This answer restricts the ways dogs could have arrived by boat, making it harder to prove the author correct. The author said the dogs probably arrived during a trading expedition, but they were open to other ways.
- Same as C. This adds a necessary condition to the conclusion. Necessary conditions always make it harder to prove something right. They add an additional way to fail, but yet don’t help you prove the sufficient condition.
- CORRECT. If this isn’t true, then there’s no reason to think the dogs traveled by boat instead of overland.
Negation: Boat travel between the coastal regions of Western Mexico and Peru was no easier than land travel.
This is a really stupid question. “A” should be correct. Negation: Hairless dogs HAVE been found in regions other than Western Mexico and Coastal Peru. Where? Maybe the dogs came to Peru from Columbia/Brazil/Bolivia? Passage from these counties isn’t difficult at all. Then that would mean they could’ve been introduced to Peru by land from a neighboring country and not from Mexico. Case closed.
You need to negate answers in the least useful way. For example, suppose a hairless dog was found in Mongolia and never left. That is a negation of A, but it doesn’t destroy the argument.
The negation of the right answer will wreck the argument no matter how you negate it. You can’t use only favorable negations to prove an answer.
Note: This is an old comment but I wanted to clarify the point.
I don’t understand how you guys made assumption from A that the regions mentioned in A outside of Western Mexico and costal Peru have no contact with WM and CP? I see “what if” mentioned which means none of you guys are sure the “no contact” assumption is true. Couldn’t be that the dogs were imported by boat from some remote regions to these two places? I bet transporting by boat from California to WM or CP wasn’t that hard centuries ago by the fact that Europeans transported from Europe to America centuries ago…
You want to negate in the least useful way. That’s why I chose a region with no contact with the Americas. For example, to get to law school, which of these is necessary:
A 180 –> negates to 179
Applying –> negates to not applying
You’ll do just fine with a 179 so a 180 isn’t necessary. But if you don’t apply, you don’t get in. So applying is necessary.
Certainly a 120 isn’t a 180 but that’s not how you negate. You negate in a way that makes the original statement only slightly untrue. Basically make the negation as useless as possible. If it still wrecks the argument nonetheless, then and only then is it the right answer.
Note: This is an old comment but I wanted to clarify the point.
Hey all!
No need to publish this comment… just want to say there’s a typo: “effect” should be “affect.”
Thanks for the catch James! The page has been updated.
I don’t understand the negation for 18 a.
The statement says that “hairless dogs have never been found anywhere except in the regions of western mexico and peru.” Wouldn’t that negate to “hairless dogs have been found in places other than the regions of western mex..”
This would weaken the argument by showing that the assumption of how the dogs arrived in new mexico and peru could be incorrect.
If the negation of (A) were something to the effect of “there are regions of the world that were in contact with western Mexico and Peru where the trait of hairlessness in dogs emerged,” then yes, it would weaken the argument. We’d then know that there are other possible ways that hairless dogs emerged in western Mexico and/or Peru–perhaps through trade by these regions with whom they did have contact. However, as you’ve pointed out, the negation of (A) is actually that the trait emerged in any region outside western Mexico and Peru, regardless of whether or not it was contact with these two regions at the time.
What this means is that if we find just one country where hairlessness emerged in dogs and it wouldn’t be possible for that trait to somehow be carried over to western Mexico and Peru centuries ago, then this negation wouldn’t weaken the argument. So, what if one of those regions had absolutely no contact with western Mexico and Peru centuries ago–like the regions that are mentioned in the explanation? The argument wouldn’t fall apart, because then the conclusion wouldn’t be threatened.
got it! thanks
I still don’t see how that negates the argument. There isn’t anywhere in the world that can’t reach Western Mexico or Peru; in fact, native people from Central Africa (your example of a place too remote) DID wind up in Mexico via slave ships, on a fairly regular basis, in the 15th & 16th Century.
If these dogs were found anywhere else on the planet, then they may not have travelled between Peru and Mexico by boat; they may have originated at a shared third country, and been brought separately.
The argument isn’t about what is possible. The argument’s entire premise is that the dogs didn’t go overland because it is hard to do so. And therefore they travelled by boat.
But if it is harder to go by boat, then the argument falls apart. Boat travel would still be possible, but suddenly land travel is more likely because it is in fact easier.
Note: This is an old comment but I wanted to clarify the point.
“A” should be a good answer because maybe the dog came from a third place.
And if you want argue that they could be from a place that can’t reach Peru/ Mexico (and therefore this isn’t an assumption need), it still would show us that maybe hairlessness in dogs isn’t as rare as we thought if in two separate places dogs are developing this trait. And therefore maybe the dogs in Peru and Mexico independently developed this trait.
Either way we kinda need it to be true that there aren’t more hairless dogs walking around …
You’re right to point out the reason that the negation of (A) doesn’t seriously undermine the argument: what if hairlessness emerged in a country that had no contact with Peru or western Mexico? Then the reasoning and conclusion of the stimulus are unaffected (I’ve discussed this concept more fully in my reply to Tova’s comment below).
As for your second point, you’re bringing in the following unwarranted assumption: “if hairlessness emerges in any region outside western Mexico and Peru, then it’s not so rare that it couldn’t independently develop in different regions”. There’s nothing in the stimulus that tells us that’s the case. Maybe it could exist in 1-2 (or more) other regions and still, the trait would be rare enough that it’d be unlikely for hairlessness to independently develop in two separate regions.