Logical reasoning PrepTest 144 · Section 4 · Question 18

Incorrect. This answer is very tempting—it seems to rule out an alternative possibility (that the hairless dogs were transported from a different area entirely). And while it does that, it does it in a way that's too extreme to be necessary. Hairless dogs could have been found millennia ago and then died out, or they could have been in areas so remote that there's no conceivable way they could have ended up in Mexico and Peru at the time they emerged, and the argument could still function.

Incorrect. The relevant trading expeditions are just those between Mexico and Peru, so it's not necessary that most of the trade goods coming into Mexico from everywhere were via boat for this argument to work. As long as a significant amount of trade goods from Peru came into Mexico via boat, the argument can still work.

Incorrect. The conclusion leaves open the possibility that transportation between Mexico and Peru via boat could have been done for other reasons when it says "probably during trading expeditions," so it's not necessary to assume that this travel was only for trading.

Incorrect. There's no need for the dogs to be a part of the trade, or that they were traded for goods other than other dogs, for the argument to work. As long as the dogs were on the boats, the conclusion can be correct.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Mexico and Peru have hairless dogs. These dogs were never wild and the trait unlikely developed twice. At the time when they were bred, travel over land was extremely difficult, so the dogs were probably brought from one area to another via boat.

Answer Anticipation:
While a lot wordier than arguments that fall into the same pattern, this stimulus very much falls into the phenomenon/explanation camp! The hairless dog breed that is unlikely to have developed independently located in two regions needs an explanation, and the argument settles on them being transported from one region to another via boat (note that it doesn't say where the point of origin between Mexico and Peru is).

Whenever an argument concludes one explanation, we should start to think about alternatives. And here, the stimulus provides one—that the dogs were transported via land. While it does establish that this travel would be "extremely difficult," that doesn't eliminate it completely as a possibility. And it never establishes that travel by boat would have been any easier.

While the argument does assume that the dogs weren't transported by any means other than boat, it's unlikely that there are any options other than land and sea (they didn't exactly have planes centuries ago), so the correct answer will likely establish that travel by sea between Mexico and coastal Peru was more common/easier than travel by land at the time that these dogs emerged.

Answer Explanation:
This argument provides a reason to believe that the explanation in the conclusion is more likely than one alternative, and it's based on the information from the stimulus. The reason the argument believes that boats transported the dogs instead of the dogs being transported over land is that the land route was extremely difficult. If the boat route was just as or more difficult, then there's no reason to think that that means of transportation is more likely, and the argument falls apart.

Key Takeaway:
Whenever an argument can be seen through a phenomenon/explanation lens, the correct answer will generally deal with alternative explanations. When an alternative explanation is raised in the stimulus, there's a good chance that it'll be the alternative that the correct answer deals with. When the argument seemingly rules out that alternative, make sure that it actually does so instead of just making it seem unlikely or implausible.