In one study, hospital patients' immune systems grew stronger when the patients viewed comic videos. This indicates t...

RyanW on July 28, 2018

Errors in Reasoning

Hi, I'm having a hard time with this problem and seeing why 'A' would be right. Thanks!

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Christopher on July 29, 2018

@EvanW, this is an "error in reasoning" question, so you're looking for the answer that weakens the given argument logically. This often occurs by re-interpreting a piece of information or undermining a key premise.

With this question, the conclusion is that hospital patients who are more prone to laugh were helped more by laughing a little bit than those who are less prone to laugh were helped by laughing a lot. So let's look at how they got there.

First, hospital patients who were shown comic videos showed a tendency to recover more quickly, which is used to suggest that laughter helps with recovery.

Second, hospital patients who were prone to laugh showed a more significant benefit to laughing.

The author uses this to conclude that a little laughing from a happy person is more effective than a lot of laughing from a less happy person.

As you can see, there's a logical leap between the second premise and the conclusion, so we're looking for the answer that points that out. (A) does this by pointing out that if laughing helps with recovery, it is possible that the people who were prone to laugh recovered better because they laughed more when shown the comic videos. This provides an alternate interpretation of a premise, which undermines the conclusion.

Does that help?

RyanW on July 29, 2018

Yes that clears things up, thank you!

jack515 on January 2, 2019

In the question it says that the patients who had a tendency to laugh more to begin with laughed less than the other patients. "helped more in their recovery from illness even when they laugh a little than other patients are helped when they laugh a greater amount" then the answer goes on to say that the patients who have the tendency to laugh more did in fact laugh more at the video. does this not contradict the part of the question i quoted above?

Ravi on January 3, 2019


Great question. The portion of the stimulus that you quoted is part of
the argument's conclusion. This is a flawed conclusion, as the only
premise we're given in the argument is that having a tendency to laugh
is correlated with gaining immune system strength.

The problem with the argument's conclusion is that it is taking a
correlation between the tendency to laugh and immune system strength
and falsely inferring that having a high tendency to laugh causes
larger gains in immune system strength. Additionally, another flaw of
the conclusion is that it assumes that the causal impact of having a
tendency to laugh is stronger than the causal impact of the other
variable (which is how much a given patient laughed). We simply do not
know whether that is true or not, as we don't have enough information.
In fact, given the context of the argument, which states that laughter
causes better recovery, we have reason to believe that the amount of
laughter, and not the tendency to laugh, was the primary component of
aiding recovery.

Answer choice A is correct because it weakens the argument's causal
conclusion by introducing an alternative cause that is entirely
possible. It's totally reasonable that patients whose tendency to
laugh was greater to begin with laughed more at the comic videos than
did the other patients. If A is true, then the correlative effect in
the premise of the tendency to laugh being correlated with gaining
immune system strength is explained away by the causal relationship
provided in the context of the argument (laughter causing better
recovery). If this is true, then this casts serious doubt on the
author's conclusion, and this is why the argument is vulnerable to
criticism—it's overlooking this fact.

Minerva on September 14, 2019

From the explanations above, I can see why A is correct, but wouldn't B also be a flaw in this case?

Victoria on September 14, 2019

Hi @Minerva,

B is not a flaw because the passage is discussing gains in immune system strength. If the passage claimed that patients with a greater tendency to laugh to begin with had the strongest immune systems at the end of the study, this would be a flaw. But, because it discusses gains in immune system strength, this would be relative to how strong each patient's individual immune system was at the beginning of the study.

Hope this helps! Please let us know if you have any further questions.

amf on April 18, 2020

Why is D incorrect?

Victoria on May 4, 2020

Hi @amf,

As Ravi mentioned above, the flaw in reasoning is its assumption that having a greater tendency to laugh has a stronger impact on a patient's recovery than the amount a given patient laughed. There is not enough evidence provided in this passage to support this assumption. That is why answer choice (A) is correct.

Answer choice (D) is incorrect for two reasons:

(1) The passage states that patients who received greater health benefits had a greater tendency to laugh "to begin with," i.e. prior to becoming ill. Therefore, it does not follow that the health benefits a patient received influenced their tendency to laugh as the passage suggests that this tendency existed as an independent trait of each given patient.

(2) Answer choice (D) suggests a flaw in the passage's causal reasoning whereas the real flaw in the passage is the lack of evidence provided regarding the amount that patients laughed at the comic videos.

Hope this is helpful! Please let us know if you have any further questions.