LR Question 18 Explanation
QUESTION TEXT: Medical researcher: A survey of more than 1 million…
QUESTION TYPE: Flawed Reasoning
CONCLUSION: Mild sleep deprivation is probably healthy and boosts the immune system.
REASONING: People who sleep at least 8 hours a night have more diseases than those who sleep a lot less each night.
ANALYSIS: This argument confuses correlation for causation. Whenever there is a correlation, there are four possibilities:
- Sleep does cause illness.
- Illness causes more sleep.
- A third factor causes both illness and sleep.
- The correlation is a coincidence.
On a flawed reasoning question, the right answer will describe one of the other possibilities abstractly. Here, answer A describes the third possibility.
___________
- CORRECT. This is possibility three above. Perhaps, for example, a weakened immune system causes more sleep (to repair the immune system) and more infections (because the immune system is weak).
- The argument didn’t say that only sleep affects health. There could easily be other factors, such as genetics, exercise, diet, etc.
- This is fancy language for taking a necessary condition to be a sufficient condition. That didn’t happen here.
- This is saying: if hammers can cause injury, then there will be a correlation between hammers and injury.
That’s flawed reasoning (hammer owners might be careful with their hammers), but it’s not the flawed reasoning used in the argument. - This is a different flaw.
Example of flaw: Smoking doesn’t cause boils. Therefore, smoking is safe.
More Resources for Flaw Questions
- Flaw drills: Use these to practice making examples of abstract flaws.
- Intro Course lesson: This intro course lesson covers Flaw questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers flaw questions.
This is one of those situations where I should be more disciplined, recognize the correlation v. causation question type, and anticipate the correct answer touching on one of those 4 possibilities you wrote, rather than dive into mental gymnastics.
To try to hurt the argument, I liked E because let’s say sleep deprivation leads to heart palpitations and blood clots – isn’t it reasonable to view those negative consequences as unhealthy?
I guess negative consequences is NOT the exact same as unhealthiness and sleep deprivation could just as easily have negative consequences that aren’t related to health (poor judgement, etc.), but 80-some seconds budgeted per question, it’s easy to get trapped by that sleight of hand between negative consequences and unhealthiness.
The problem is that the stimulus said “illness”. That’s a broad word that includes *all* health problems, including blood clots etc. Illness doesn’t refer only to contagious disease
E would be the answer if argument had said “those who sleep have more heart disease, so sleeping less is healthy”
Couldn’t E be correct here?
The author is failing to consider that just because a specific negative consequence (frequency of illness) is not associated with a given phenomenon (sleep deprivation), that phenomenon may have other negative consequences.
Consider this situation: one in two people who do get adequate sleep get a cold. However, one in three people who do not get adequate sleep develop severe heart problems. The rate of illness is lower for people who are sleep deprived, yet sleep deprivation could be associated with a much more serious illness (“other negative consequences”). This situation could be entirely consistent with the results of the survey.
By failing to consider this, the the author’s conclusion that sleep deprivation is “not unhealthy” is substantially weakened.
Also, it would seem that your “smoke doesn’t cause boils, therefore smoking is safe” example would actually apply here. “Sleep deprivation is not associated with any sort of illness at as high of a rate as is adequate sleep. Therefore, sleep deprivation is not unhealthy.”
First, just a more general point: it’s important to remember that at the beginning of every LR section, LSAC writes that more than one choice could conceivably answer a question. It’s your job to choose the best answer. So, to say that an answer choice “could” answer a question, isn’t grounds enough to label it the correct answer. It must also be better than the other answer choices.
So, that being said, there are a couple issues with (E). What exactly would the “specific negative consequence” described in the answer choice be? A higher frequency of illness than those who get adequate sleep? That seems more like a comparison than a specific negative consequence. Also, is the author of the stimulus really assuming that just because there’s a lower frequency of illness among that group, that there are no other negative consequences (the answer choice says that the stimulus is overlooking the possibility that inadequate sleep “may have other negative consequences”).
If we break this answer choice down into its component parts, we have to do a lot of mental gymnastics to make it fit the stimulus, whereas (A) doesn’t require that kind of work.
The medical researcher had mentioned “not unhealthy” which seems pretty broad. He didn’t say that mild sleep deprivation doesn’t cause illness; that would have been fine and I then would completely understand your point above. However, with the phrasing that they did actually use, it would seem that based on the fact that people that sleep less get fewer illnesses – conclusion: sleep deprivation is unhealthy. That would be open to the flaw that perhaps there are other negative consequences of sleep deprivation…
Thanks for bringing this up, because re-reading my initial comment, I’d actually like to backtrack on the first issue I mentioned with (E): you could say that “greater frequency of illness” is a somewhat specific negative consequence. My other point still stands though: the author does not fail to consider that the “phenomenon” (sleep deprivation) has other negative conquences. All the author is concluding is that sleep deprivation is not unhealthy. Maybe the author would readily agree that sleep deprivation has negative consequences — irritability, rash judgments, etc.
Read Powerscore’s and Manhattan Prep’s explanation of this question, but yours made the most sense. Thanks!
This is a causation correlation question and the answer is not E because —
“The author does not fail to consider that the “phenomenon” (sleep deprivation) has other negative conquences. All the author is concluding is that sleep deprivation is not unhealthy. Maybe the author would readily agree that sleep deprivation has negative consequences — irritability, rash judgments, etc.”
Thanks for this explanation–it helped me isolate my issue with the question to the fact that I was thinking the argument was still unreasonably conflating two potentially different consequences, because I was going “even if there isn’t a higher level of *disease* that doesn’t mean it isn’t medically unhealthy, disease is a pretty specific concept,” until I realized the question didn’t say that at all, it just said “illness,” which is absolutely justifiable as a substitute for unhealthiness. My understanding of how LSAT questions are written is that even though the instructions say that more than one choice could conceivably answer the question, they can’t actually leave room for subjective judgments, so a question that asks how an argument is “most” vulnerable to criticism will still have to be written so that four of the answers are objectively wrong. While I could understand why A was correct, I couldn’t figure out why E was *incorrect*, so thank you for clarifying that!