Frederick Snyder proposed the idea that rapid eye movement (REM) sleep

Question

Frederick Snyder proposed the idea that rapid eye movement (REM) sleep serves a sort of sentinel function because it is a state of much neural activity. The hypothesis is that episodes of REM sleep allow an animal to be ready to escape once awake should a predator attack, and that the brief periods of wakefulness associated with REM sleep also serve an antipredator function.

The sentinel hypothesis is appealing in many respects. Mammals in REM sleep are clearly more physiologically prepared for wakefulness than are those in deep slow-wave (SW) sleep. Furthermore, humans and rats can detect and process information to a surprising degree during REM sleep. Paradoxically, however, thresholds for arousal from REM sleep tend to be higher than from SW sleep. Additionally, the brief periods of wakefulness associated with REM sleep may not be frequent enough to have much benefit from an antipredator perspective.

Moreover, the hypothesis has never really been tested, and its predictions are not obvious. One would expect that REM sleep would be more prominent in species that suffer high predation or would become so when the perceived risk of predation increases. However, this prediction does not hold. One would also expect that an increase in predation risk would lead to shorter cycles of REM sleep and thus more arousals to wakefulness.

Based on the information in the first paragraph, it is most reasonable to attribute to Snyder which of the following assumptions?

A. Sleep that involves much neural activity is the least restful form of sleep.
B. The greater the amount of an animal's neural activity, the sharper its perception of the surrounding environment.
C. REM sleep occurs in most animal species and serves to protect them against predators.
D. REM sleep generally does not occur in animals except when they fear a high risk of predation.
E. Animals waking from sleep during low levels of neuroactivity are unlikely to achieve the fastest possible responses.

Which of the following claims about SW sleep can most reasonably be inferred from the passage?

A. Mammals are less sensitive to environmental stimuli during SW sleep than during REM sleep.
B. Mammals tend to enter SW sleep only when they perceive little or no risk of predation.
C. To be physiologically prepared to awaken, mammals in SW sleep must make a transition to REM sleep.
D. The lowest levels of neural activity during sleep tend to occur during SW sleep.
E. Some stimuli intense enough to awaken an animal from SW sleep may not awaken the animal from REM sleep.

The passage is primarily concerned with

A. comparing the role of REM sleep with that of SW sleep
B. describing the role of neural activity in antipredator behavior
C. discussing a hypothesis about the role of REM sleep
D. exploring competing hypotheses about the role of REM sleep
E. suggesting some consequences of a hypothesis concerning the causes of REM sleep

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Show Answer Question #1

Official Answer

E

Show Answer Question #2

Official Answer

E

Show Answer Question #3

Official Answer

C

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GMATNinja · Accepted Answer

Question 1

There's nothing in the first paragraph (or the entire passage for that matter) about how restful REM sleep is compared to other types of sleep, so (A) can be eliminated.
 
The second paragraph does mention that "humans and rats can detect and process information to a surprising degree during REM sleep". However, that doesn't necessarily imply that there's a direct relationship between neural activity and sharpness of the animal's perception of the surrounding environment. And since this information isn't presented in the first paragraph anyway, we can rule out (B).
 
There's nothing in the first paragraph (or in the passage) indicating that REM sleep occurs in MOST animal species, so (C) has to go.
 
The final paragraph suggests that (D) is in fact false: "One would expect that REM sleep would be more prominent in species that suffer high predation or would become so when the perceived risk of predation increases. However, this prediction does not hold."

Regardless, there's nothing in the first paragraph or in the entire passage about the relationship between fear and REM, so (D) is out.
 
The first paragraph states that REM "is a state of much neural activity" and that "episodes of REM sleep allow an animal to be ready to escape once awake should a predator attack." The implied assumption here is that episodes of "much neural activity" allow an animal to be ready to escape -- and being ready to escape a predator implies that there's a reasonably fast response time (the sleeping animal reacts before the predator gets to them).

If Snyder is assuming that "much neural activity" means fast response, then he must also be assuming that less neural activity would mean slower response -- which is basically what (E) says in a different way. So (E) is our winner.

I hope that helps!

chetan2u · Answer

First let us see why E is a clear winner here. 
In REM sleep, the animal seems to be also performing look out for perceived dangers due to much neural activity associated with the sleep. 
The hypothesis is that the animal is more ready to escape incase of an attack by predator during REM sleep

So REM sleep allows faster reaction incase of an attack, and Synder associates it further with the higher neural activity in REM sleep. 
Clearly his assumption is that those waking up for sleep during low levels of neural activity do not seem to possess faster reaction at that moment.
If those waking up from sleep with low neural activity were similar in their response, REM sleep would not be associated with sentinel duties too.

However, B leaves out neural activity in sleep and talks of general neural activity.

DrAnkita91 · Answer

why option B cannot be the answer? Is it because "the comparison about greater and lower neural activity" is not discussed in the first para?

I feel option B and D are very close.
Can some one help me out in this?

Regards
Dr Ankita

chiplesschap · Answer

The passage only says REM is a state of much neural activity and that it helps ready an animal to escape once awake should it be attacked by a predator. Even if we assume that REM (and therefore higher neural activity) makes animals perceptive of surrounding environments, we cannot conclude that increased neural activity *will* sharpen their perception of surrounding environments.

AnayB · Answer

Hi Experts,

I have tried understanding in terms of the context -
REM -> lots of neural activity ; option E talks about waking up during low levels of neuro-activity sleep which is opposite of REM , how is this the assumption ?

Could someone please explain why option E is the right answer?

Thank-you for taking out the time to explain the same.

AvikSaha · Answer

Hi  MartyMurray

Sorry to ping you again.

Can you please explain the doubt here why B can't be the correct option for below question:
1. Based on the information in the first paragraph, it is most reasonable to attribute to Snyder which of the following assumptions?

A. Sleep that involves much neural activity is the least restful form of sleep.
B. The greater the amount of an animal's neural activity, the sharper its perception of the surrounding environment.
C. REM sleep occurs in most animal species and serves to protect them against predators.
D. REM sleep generally does not occur in animals except when they fear a high risk of predation.
E. Animals waking from sleep during low levels of neuroactivity are unlikely to achieve the fastest possible responses.

Raman109 · Answer

1. Based on the information in the first paragraph, it is most reasonable to attribute to Snyder which of the following assumptions?

The critical thing to remember is that we only talk about the 1st Para. Moreover, the assumption for what? In conclusion. What conclusion? (REM) sleep serves a sort of sentinel function because it is a state of much neural activity. How? REM sleep allows
1. an animal to be ready to escape once awake should a predator attack and 
2. serve an antipredator function.

A. Sleep that involves much neural activity is the least restful form of sleep. - We don't know. Out of scope.

B. The greater the amount of an animal's neural activity, the sharper its perception of the surrounding environment. - "Perception of the surrounding environment" differs from "an animal to be ready to escape once awake should a predator attack." The argument is that the REM acts as a safeguard against predation. How? There is high neural activity, and the animal is ready to escape once it is awake.

The argument doesn't specifically discuss "the sharper" or "dullness" of its perception. This is out of scope.

C. REM sleep occurs in most animal species and serves to protect them against predators. - out of scope.

D. REM sleep generally does not occur in animals except when they fear a high risk of predation. - timing is out of scope.

E. Animals waking from sleep during low levels of neuroactivity are unlikely to achieve the fastest possible responses. - ok.

kayarat600 · Answer

What possible reason could question to be the last option

MonishBhawale · Answer

answer for Q1 is E
as when we negate the statement" Animals waking from sleep during low levels of neuroactivity are unlikely to achieve the fastest possible responses"
 the entire argument falls apart

mounaturki · Answer

For this question :

Which of the following claims about SW sleep can most reasonably be inferred from the passage?

A. Mammals are less sensitive to environmental stimuli during SW sleep than during REM sleep.
B. Mammals tend to enter SW sleep only when they perceive little or no risk of predation.
C. To be physiologically prepared to awaken, mammals in SW sleep must make a transition to REM sleep.
D. The lowest levels of neural activity during sleep tend to occur during SW sleep.
E. Some stimuli intense enough to awaken an animal from SW sleep may not awaken the animal from REM sleep.

I do not understand why E is the correct inference to make. It's not mentioned in the text that an animal during SW sleep is more likely to respond to stimuli than during REM sleep. I don't understand why A is wrong

bumbleBee3445 · Answer

Hi @GMATNinja, @chetan2u,

Could you please explain 2nd question?
I selected option A, and I am unsure how option E can be inferred from the passage.

GMATNinja · Answer

Question 2

The passage states the following: "thresholds for arousal from REM sleep tend to be higher than from SW sleep." In other words, all else equal, it's easier to wake up an animal from SW sleep than from REM sleep.

For example, some moderately loud noise might be  enough  to wake up the animal from SW sleep (where the threshold is lower). That same noise might   not   be enough to wake up the animal from REM sleep (where the threshold is higher).

And that's basically what (E) says: some stimuli (noises, for example) intense enough to awaken an animal from SW sleep may   not   awaken the animal from REM sleep.

There's nothing in the passage comparing sensitivity to environmental stimuli in SW sleep vs REM sleep. (A) might be true, but there's no evidence one way or the other.

So (A) is out, and (E) is our winner.

SudsMeister · Answer

I am still quite conflicted about Q1.

Snyder states that: REM has high levels of neuroactivity which leads to escaping faster.
If REM's high levels of neuroactivity ----> Escape faster
Then we cannot say that If less/no neuroactivity -----> slower/unlikely to escape. It is because "If A, then B", doesn't imply "If not A, then not B".

But option E implies the latter, and we cannot assume it.

Even negation doesn't work as per me. Snyder says: REM's high neuroactivity serves a sentinel function as it helps one escape attacks.

Let's negate E: Low levels of neuroactivity are likely to achieve the fastest possible responses. Doesn't break Snyder's claim that REM's high neuroactivity serves as a sentinel function. Syner doesn't say REM is the only exhaustive way of escaping attacks. Regardless of whether low levels of neuroactivity help escape attacks or not, we are concerned about REM's high level of neuroactivity being able to do it or not.

GMATNinja · Answer

For a full explanation of Question 1, check out this post: https://gmatclub.com/forum/frederick-sn ... l#p3360347.

manish8242 · Answer

I had one problem with the E option for Q1. 'Fastest' word in the sentence. Synder is not assuming this neither it is necessary to assume. It's okay awakening from low level of neuroactivity might not be the fastest so what? Still it may be helpful to a certain degree. We only know comparison between low and high level of neuroactivity. But it's not binary as well. so assuming low level is not the fastest is not necessary condition here

Frederick Snyder proposed the idea that rapid eye movement (REM) sleep

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Frederick Snyder proposed the idea that rapid eye movement (REM) sleep

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