Question


In an experiment, volunteers walked individually through a dark, abandoned theater. Half of the volunteers had been told that the theater was haunted and the other half that it was under renovation. The first half reported significantly more unusual experiences than the second did. The researchers concluded that reports of encounters with ghosts and other supernatural entities generally result from prior expectations of such experiences.

Which of the following, if true, would most seriously weaken the researchers’ reasoning?

(This question is from the Official Guide. Therefore, because of copyrights, the complete question cannot be copied here. The question can be accessed at GMAT Club)

Difficulty: Medium

Accuracy: 70%

Based on: 6509 sessions

Solution


The Story

In an experiment, volunteers walked individually through a dark, abandoned theater.
There was an experiment. In the experiment, people walked through an abandoned theater. They walked individually.

Half of the volunteers had been told that the theater was haunted and the other half that it was under renovation.
Half the people were told that the theater was haunted, and the other half were told that it was under renovation.

So the volunteers were divided into two groups. The two groups were given different information about the same theater.

The first half reported significantly more unusual experiences than the second did. 
The first group (the group which was told that the theater was haunted) reported many more unusual experiences than the second group.

I’m wondering what experiences constitute ‘unusual experiences’. Perhaps we’ll find out.

The researchers concluded that reports of encounters with ghosts and other supernatural entities generally result from prior expectations of such experiences.
The researchers reached a conclusion based on the experiment. They concluded that reports of encounters with ghosts resulted from expectations of such experiences. (Basically, the fact that the first group was told the theater was haunted led to the higher number of reports of paranormal activities.)

Gist:

  1. Researchers conducted an experiment. 
  2. Many volunteers walked through an abandoned theater individually. 
    • Half of them were told that the theater was haunted. 
    • The other half were told that the theater was under renovation. 
  3. A lot more of the people who were told that the theater was haunted reported unusual activity in the theater. 
  4. The researchers concluded that generally people report experiencing paranormal activity as a result of expectation of paranormal activity.

Researchers’ logic:

  1. We told half the volunteers that the theater is haunted
  2. (That’s why they expected paranormal activity)
  3. That’s why more volunteers from this half reported paranormal experiences 

More people from the first group reported paranormal activity because we told them that the theater was haunted. Because we told them the theater was haunted, they expected the theater to be haunted.

Gap(s) in logic

  1. This is a classic case of a causation-correlation flaw. It is possible that:
    • Maybe their experience was not impacted by what the researchers told them. It was a coincidence that more people from the first group reported paranormal activity.
    • The first group consisted of more people who believed in the paranormal from before the experiment.
    • The first group actually experienced more paranormal activity. This might sound far fetched, but ghosts do exist, don’t they?
      (Psst … what’s that behind you?)
  1. I mentioned this while explaining the passage too. The first half experienced more ‘unusual activities’. The passage did not elaborate on what kind of activities were considered unusual. Maybe they did not consider the experiences paranormal.
    E.g. Maybe they saw a dog walking around wearing reading glasses, and they found it unusual. I mean that would be pretty unusual, no?
  2. The results of the experiment perhaps cannot be generalised.

Question Stem


Which of the following, if true, would most seriously weaken the researchers’ reasoning?

What is the researchers’ reasoning?

X: We told half the volunteers that the theater is haunted

Y: More volunteers from this half reported paranormal experiences 

X caused Y: More volunteers from that half reported paranormal experiences because we told them that the theater is haunted.

This causal relationship is something the researchers have concluded. They actually bring in another aspect between X and Y – expectation.

We told them → They expected → Reported more paranormal experiences

Framework: The correct answer should indicate that the reason for the different experience by the two groups was not related to the different information they got initially.

Answer choice analysis


Answer Choice: A

Incorrect

Selected by: 4%

First off, let’s consider the following statement:

A’. None of the volunteers in the experiment believed that the unusual experiences they reported were supernatural.

What impact do you think this statement has?

This statement weakens the reasoning. It highlights the second gap I mentioned above – ‘unusual’ doesn’t necessarily mean ‘supernatural’.

What about this statement:

A’’. None of the volunteers in the second half had any unusual experiences.

Which one is the second half?

The half that were told that the theater was abandoned.
The half that reported a lot fewer unusual experiences.

This answer choice mildly strengthens the reasoning. Many volunteers in the first half had unusual experiences; none of the volunteers in the second half did. So, perhaps the information that the researchers gave the volunteers initially impacted their experiences.

Now, back to the original answer choice.

I believe that one is more in line with the second variation I mentioned above.

So, 

  1.  that half reported a lot fewer unusual experiences
  2. on top of that, the experiences they had were not even supernatural (from this option)

I start to believe that the information the volunteers were given at the beginning did have an impact on what they experienced.
This answer choice mildly strengthens the reasoning.


Answer Choice: B

Correct

Selected by: 70%

Which one is the first half?

The half that were told that the theater was haunted.

The half that reported a lot more unusual experiences.

The logic of the researchers was:

We told them that the theater was haunted → That’s why they expected paranormal activity → That’s why they reported more experiences of paranormal activity

This answer choice weakens the first link. If these volunteers believed that the researchers’ statement was a lie, they would not expect paranormal activities on hearing that lie. So, their experiences would not have been impacted by their expectations.

Now, you might think: Although the volunteers believed the researchers’ statement was a lie, maybe the idea got implanted in their minds (Inception style), and that’s why they reported more unusual experiences. So, this answer choice doesn’t weaken.

That could be true. So, this answer choice doesn’t destroy the reasoning. It doesn’t ascertain that 

There’s a flaw in this reasoning.

The researchers’ conclusion includes the phrase “prior expectations of such experiences”. The discussion here is about what the volunteers expected. Their expectations would be based on what they believe, and not what is going on in their subconscious mind.


Answer Choice: C

Incorrect

Selected by: 11%

First off, let’s be clear about what this statement means.

The answer choice is not in line with the gap 1b I pointed out above. The option is not telling us that the first group believed more in paranormal activities from before than did the second group.

Answer choice: The volunteers within each group varied in their prior beliefs. 

So, in terms of level of belief in supernatural activities, people in both groups lay across the spectrum. There was diversity in both groups.

Once I learn this new piece of information, I’m thinking that the reason for the difference in reporting was not because of their pre-existing beliefs at least. By taking away one gap I identified earlier, this answer choice strengthens the argument. 

.


Answer Choice: D

Incorrect

Selected by: 14%

No impact.

This answer choice is different from the second gap I mentioned above. In the gap, I discussed how the term ‘unusual’ is quite vague and what the volunteers term as unusual, they may not even consider supernatural.

This answer choice is talking about the truth behind the experience.

E.g. 

  1. A volunteer saw a white cloth flying in the air. 
  2. The volunteer believed that the cloth was a ghost and reported the experience.
  3. Now we learn that the cloth was a curtain that was swaying in the wind.

That last piece is irrelevant to the argument. 

The issue here is: 

Did the volunteer believe that the flying cloth was a ghost because he expected some supernatural activity? 

Or would he anyway have believed the flying cloth to be a ghost, even if he did not expect any supernatural activity?

The issue is not whether the volunteer was correct in believing that the flying cloth was a ghost. 

Why the cloth was actually flying is irrelevant to the argument.


Answer Choice: E

Incorrect

Selected by: 1%

No impact. The argument is about the volunteers and their expectations. What the researchers believed is irrelevant.

If you have any doubts regarding any part of this solution, please feel free to ask in the comments section.

Anish Passi

GMAT Coach

With over a decade of GMAT training experience, top 1 percentile scores on the CAT and GMAT, and a passion for teaching, I’d like to believe I am quite qualified to be a GMAT coach. GMAT is learnable, and I help students master the GMAT through a process-oriented approach based on logic and common sense. I offer private tutoring and live-online classroom courses. My sessions are often sprinkled with real-world examples, references to movies, and jokes that only I find funny. You’ve been warned 🙂

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