Bunuel
For the last several years, the most popular breed of dog in the United States has been the Labrador Retriever. An official at a national association of dog breeders concluded that the breed is the most popular only because of the Labrador Retriever's friendly disposition and the ease with which the dogs can be trained.
Which of the following, if true, would cast the most serious doubt on the accuracy of the official's conclusion?
A. The Labrador Retriever is closely related to the Golden Retriever, another popular breed in the United States.
B. Labrador Retrievers have been trained in a number of useful ways, such as to serve as guide dogs or as hunting companions.
C. Some people do not like Labrador Retrievers because they can be quite large as adults and often chew furniture when they are puppies.
D. The Australian Shepard is another friendly and easy to train dog breed, yet it does not have nearly the popularity of the Labrador Retriever.
E. No recent popular television shows have featured a Labrador Retriever.
Official Explanation
Answer D.
In the stimulus, the dog breeder official concludes that Labs are the most popular dog only because they are friendly and easily trained. In other words, the friendliness and ease of training of the Labs causes their popularity. In any weaken question with a causal argument, your task is to show that the causality is not properly draw – in this case that the friendliness and training ease are not alone causing the Lab to be the most popular dog breed. Choice (D) gives us reason to believe that this is true. If the Australian Shepard has the same characteristics as the Labrador Retriever, but does not have the same outcome (i.e., the high popularity), then there must be other factors involved (e.g., availability, reputation, etc.) that cause the Lab to be the most popular breed.
None of the other answer choices work to sever the causality as it is stated in the stimulus. Choice (A), (C), and (E) are out of scope – we do not care that the Lab is related to the Golden Retriever, nor that some people do not like the Lab, nor that the Lab has not shown up much on TV recently.
Choice (B) may actually strengthen the argument by confirming one of the useful and popular characteristics of the Lab – namely the ease with which the breed is trained. Since this is a weaken question, Choice (B) is incorrect.