Scientific advances in the latter half of the twentieth century have

Question

Scientific advances in the latter half of the twentieth century have allowed researchers to study the chemical activities taking place in the human brain during the sleep cycle in more detail. In the 1970s, Jacobs employed these advances to postulate that dreams and hallucinations share a common neurochemical mechanism with respect to the neurotransmitters serotonin and norepinephrine that accounts for the observable similarities between the two states of mind. To test the theory, researchers attempted to elucidate the role of these transmitters in the normal sleep cycle and the effect of hallucinogenic drugs on them.

Serotonin appears important for managing sleep, mood, and appetite, among other functions, while norepinephrine facilitates alertness and mental focus. Both neurotransmitters are discharged in high quantities only during waking states. At the onset of sleep, the neurons that release these neurotransmitters become less active, allowing the brain to enter the three non-rapid eye movement (non-REM) stages of sleep. The non-REM stages typically are not associated with normal dreaming, though parasomnias, such as sleepwalking and confusional arousals, are most common during stage 3. When the brain is ready to enter the fourth stage, REM, which is strongly associated with dreaming, the levels of these two chemicals drop virtually to zero. The Jacobs hypothesis held that the absence of norepinephrine was required to enable the brain to remain asleep, while the absence of serotonin was necessary to allow dreaming to occur

Lysergic acid diethylamide, or LSD, is a semi-synthetic psychedelic drug which causes significant alteration of the senses, memories and awareness; at doses higher than 20 micrograms, it can have a hallucinogenic effect. LSD mimics serotonin well enough to be able to bind at most of the neurotransmitter’s receptor sites, largely inhibiting normal transmission. In addition, the drug causes the locus ceruleus, a cluster of neurons containing norepinephrine, to greatly accelerate activity. If the drug stimulates norepinephrine, thereby precluding sleep, and inhibits serotonin, which Jacobs had postulated was a necessary condition for dreaming, then the resulting hallucinations could merely be “dreaming while awake.” The research thus far is promising but inconclusive; future scientific advances should allow this theory to be tested more rigorously.

Although scientists still have much to discover about the chemical complexities of the brain, serotonin appears important for managing sleep, mood, and appetite, among other important functions, while neurons release norepinephrine to facilitate alertness and mental focus. Both are discharged in high quantities only during waking states. At the onset of sleep, the activity levels of neurons that release both the neurotransmitters drop, allowing the brain first to enter the four non-rapid eye movement (Non-REM) stages of sleep. When the brain is ready to enter the fifth stage, REM, which is associated with dreaming, the levels of these two chemicals drop virtually to zero. The Jacobs hypothesis held that the absence of norepinephrine was required to enable the brain to remain asleep, while the absence of serotonin was necessary to allow dreaming to occur.    1 
 1. According to the passage, which of the following is true of the drug lysergic acid diethlyamide?

(A) Research into the drug is promising but inconclusive.
(B) The neuron receptor sites that normally bind serotonin will also bind the drug.
(C) The locus ceruleus causes the drug to affect bodily systems more rapidly than normal.
(D) The drug stimulates norepinephrine and serotonin.
(E) A person who ingests more than 20 micrograms of the drug will have hallucinations.

2 
 2. Which of the following best represents the author's primary goal in writing the passage?

(A) to outline a theory and suggest options for further research
(B) to act as an advocate for additional research to help elucidate a particular theory's validity
(C) to introduce a theoretical construct that has not yet been sufficiently proven
(D) to demonstrate the complexities involved in conducting a certain type of scientific research
(E) to articulate a hypothesis and lay out the case for proving it

3 
 3. Which of the following, if true, would most undermine the central premise of the Jacobs hypothesis?

(A) LSD does not cause as much long-term neurological damage as previously thought.
(B) Serotonin and norepinephrine rise and fall in tandem.
(C) Researchers prove conclusively that the level of norepinephrine in the brain is a significant factor in enabling the brain to sleep.
(D) Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin.
(E) The first four stages of sleep are as crucial to the process of dreaming as is the fifth stage.

4 
 4. According to the passage, all of the following are true EXCEPT

(A) Norepinephrine and serotonin are discharged only during waking states.
(B) Ingesting more than 20 micrograms of LSD will cause some people to hallucinate.
(C) Rapid eye movement is the stage of sleep during which people dream.
(D) LSD causes neurons to increase the rate at which they discharge norepinephrine.
(E) The absence of serotonin seems to be necessary in order to enable the brain to dream.

5 
 5. The passage implies which of the following about the fourth stage of sleep?

(A) One enters the fourth stage of sleep only after passing through the first three stages.
(B) Parasomnias, such as sleepwalking and confusional arousals, don’t occur during the fourth stage of sleep.
(C) “Normal” dreaming occurs more frequently during the fourth stage of sleep than during the first three.
(D) Certain neurotransmitter levels fluctuate rapidly during the fourth stage of sleep.
(E) Serotonin and norepinephrine drop as the result of the brain entering the fourth stage of sleep.

Manhattan CAT 2

Skywalker18 · Accepted Answer

Took 9 mins 30 seconds , including 3 mins 40 seconds to read .
Was in a fix in question 2 between option B and C

1 .Paragraph three is about the effects of and research results on lysergic acid diethlyamide, or LSD.
(A) The passage describes research into Jacob's theory as "promising but inconclusive," but does not make this statement about the drug LSD itself.
(B) CORRECT. The second sentence of the third paragraph says that "LSD mimics serotonin well enough to... bind at most of   receptor sites."
(C) The passage says that the drug causes the locus ceruleus to accelerate activity, the opposite of the causation suggested by this choice – that the locus ceruleus affects the body’s response to the drug.
(D) The passage states that the drug stimulates norepinephrine but inhibits serotonin.
(E) The passage says that "at doses higher than 20 micrograms, it can have a hallucinogenic effect." This means that some people may have hallucinations, but it
does not mean that everyone will, as this answer choice suggests.

2. We are asked to find the purpose of the passage. The first paragraph of the passage introduces a theory that seeks to show a link between dreams and
hallucinations based upon two chemicals. The second paragraph elaborates on the role of the two chemicals in dreams and the third paragraph does the
same for hallucinations. The third paragraph also concludes by noting that the theory remains unproven and would benefit from further testing.
(A) While the passage does outline a theory it does not suggest options for further research; it merely notes that further research would be beneficial.
(B) The author does not act as an advocate, or try to convince the audience of the need for additional research; instead, the author merely notes that further research
would be beneficial.
(C) CORRECT. A "theoretical construct" is equivalent to a theory; the author does introduce a theory that is "inconclusive," or not sufficiently proven.
(D) While the first sentence does imply that research associated with the brain is complex, the rest of the passage does not focus on this topic or attempt to demonstrate the specific complexities involved.
(E) While the passage does articulate a hypothesis, it only presents current research; it does not "lay out the case for proving it." In fact, the last sentence says
the hypothesis is "inconclusive."

3. We are asked to "undermine the central premise" of the presented hypothesis, which is summarized in the second sentence of the first paragraph. Jacobs proposed that dreams and hallucinations function via a similar brain mechanism involving the levels of two chemicals, serotonin and norepinephrine. Jacobs tried to prove this by demonstrating that the levels of
these two chemicals fluctuate in a similar fashion while both dreaming (natural state) and hallucinating (via ingestion of a hallucinatory drug).
(A) In sentence 2, paragraph 3, we are told that LSD binds "at most of the neurotransmitter's receptor sites" (italics added), indicating that we (and Jacobs)
already know that LSD does not completely inhibit serotonin transmission. This has already been taken into account, therefore, and does not undermine Jacobs' theory.
(B) The theory in question does not require serotonin to be the only chemical, or one of only a few chemicals, involved in regulating sleep. It merely proposes that two of
of the chemicals involved with sleep also function similarly when the brain is hallucinating. This choice is out of scope.
(C) This could undermine Jacobs' theory under certain circumstances, but it could also bolster the theory. Jacobs believed that the drop in norepinephrine levels
enabled the brain to sleep. This choice merely says the "levels" are significant; it does not quantify these levels, so we do not know whether this choice supports or
contradicts Jacobs' hypothesis.
(D) CORRECT. If other hallucinogens (i.e., drugs that cause hallucinations) are able to produce hallucinations without inhibiting serotonin, then the central premise of
Jacobs' hypothesis--that dreams and hallucinations function via a similar brain mechanism involving the levels of serotonin and norepinephrine--would not hold.
(E) This choice says these stages are "crucial" to the overall process of dreaming (which we can already infer from the passage - we have to fall asleep before we
dream), but it does not say anything else. Perhaps if we were told that dreaming occurs during the first four stages, when levels of the two chemicals are higher, we
might conclude that this weakens the hypothesis; the information is too vague as presented, however, to conclude anything.

4. "Except" questions require us to test the five answer choices to determine the "odd one out." It is beneficial to use the True / False technique: label each
answer choice with a T or an F and look for the odd one out (which, in this case, we should expect to be an F).
(A) CORRECT. False. The second sentence of the second paragraph says of the chemicals that "Both are discharged in high quantities only during waking states."
Later sentences tell us that the chemical levels drop during non-REM sleep, not that they disappear completely.
(B) True. The first sentence of the third paragraph says that "at doses higher than 20 micrograms,   can have a hallucinogenic effect." This is equivalent to the
statement that the dosage will cause hallucinations in some people (otherwise, we could not say that it "can have" a hallucinogenic effect).
(C) True. Sentence four in paragraph two tells us that REM (rapid eye movement sleep) "is associated with dreaming."
(D) True. The third sentence of paragraph three says that the neurons containing norepinephrine "greatly accelerate activity" when LSD is in someone's system.
Sentence one of paragraph two tells us that "neurons release norepinephrine" - so if this neuronal activity is increased, then the rate at which norepinephrine is released
must also increase.
(E) True. The last sentence of the second paragraph says that Jacobs hypothesized that "the absence of serotonin was necessary to allow dreaming to occur."

kconn · Answer

FULL DISCLOSURE - I got this q wrong initially and intitially ascribed to the ... what a stupid question/badly written viewpoint on this question which when I did re-look at this, revealed my own ignorance as this is actually an incredibly elegant question and one with a couple of great learning lessons. In an attempt to balance the negative gmat karma that this might have brought, I have broken down the analysis and learning lessons below ... I hope it is useful.

Analysis of Q#3 and why D is correct actually reveals a nice learning lesson for very high level RC.

The key learning point is that in certain situations, the use of specific words give more information on the object described than may initially seem. I missed this initially under test conditions and i can imagine it would be a trap that could be set by the exam writers to catch people out.

The question states "Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin"

Trap reaction - this is out of scope/irrelevant - what do other drugs have to do with the hypothesis about the cause of dreaming.

However - Rephrasing the question (which is a tactic that seems to work on the upper end of these questions when there are two possible answers) reveals the answer

new prompt: Drugs cause hallucinations even when these drugs do not inhibit seratonin.

Then the answer is a lot clearer; if hallucinations can occur in situations where serotonin has not been inhibited, then the cause – effect relationship which is used to support the hypothesis is weakened significantly.

The key point therefore was to identify that by definition "hallucinogenic drugs" cause hallucinations. It seems simple but under test conditions, the trap that I fell into was to gloss over the meaning of hallucinogenic and instead view this as the standard out of scope option on the basis that they are discussing "some" members in a broader group etc etc ...

Wrong and a mark dropped

- As above "Hallucinogenic" describes a both a group of drugs, but also implies that they cause a specific activity - hallucinations - that is explicitly relevant to the hypothesis in question.

The meaning is extremely important here, and requires a logic leap as if you still consider that hallucinogenic drugs are merely a group of drugs ... then it could be argued that there are certain drugs in that group who could be incorrectly described as hallucinogenic and the reason they dont cause hallucinations is because they do not inhibit seratonin. The meaning shift therefore is subtle but the key here ... hallunicinogenic drugs are describing drugs that cause hallucinations that are comparable with this case

Final point and learning lessons

Consider meaning of words especially where they describe both group and action
Rewording the question can reveal the meaning in a far clearer way sometimes
Stay humble in your review process as discipline = Freedom

- As above "Hallucinogenic" describes a both a group of drugs, but also implies that they cause a specific activity - hallucinations - that is explicitly relevant to the hypothesis in question. The meaning is extremely important here, and requires a logic leap as if you still consider that hallucinogenic drugs are merely a group of drugs ... then it could be argued that there are certain drugs in that group who could be incorrectly described as hallucinogenic and the reason they dont cause hallucinations is because they do not inhibit seratonin. The meaning shift therefore is subtle but the key here ... hallunicinogenic drugs are describing drugs that cause hallucinations that are comparable with this case Final point and learning lessons Consider meaning of words especially where they describe both group and action Rewording the question can reveal the meaning in a far clearer way sometimes Stay humble in your review process as discipline = Freedom

tastysweets2003 · Answer

1. B

A) the research is being done on the “ dream process” and not the drug so this option gets ruled out
B) it has been clearly mentioned that LSD mimics serotonin well enough to be able to bind at most of the neurotransmitter’s receptor sites
C) The locus ceruleus which will increase the alertness and mental focus which is the function of norepinephrine
D) LSd simulates norepinephrine and inhibits serotonin
E)can have hallucinations…not mandate that it will happen

2.

First passage: Jacob postulated some theory which is further taken up by the researchers to have undersatanding of role of transmitters on normal sleep and effect of hallucinogenic drugs on them.
Second :theory is described. Function of transmitter on normal sleep and the whole process how is dreaming and sleeping occur. (first part of the research)
Third passage:How LSD effect on transmitters which can result in hallucination(second part of the research)
In the end of third passage, author states that the research done in this field is promising but inconclusive.

to outline a theory and suggest options for further research( theory is outlined but no suggestions have been provided for further research)
to act as an advocate for additional research to help elucidate a particular theory's validity ( if author is advocating the research then the last statement of third passage would be not in place)
to introduce a theoretical construct that has not yet been sufficiently proven
to demonstrate the complexities involved in conducting a certain type of scientific research( no complexities involved in conducting the research have been discussed…only the theory has been explained)
to articulate a hypothesis and lay out the case for proving it( it can be considered as hypothesis but no case have been put forward to prove itas the last line suggests …theory is promising but inconclusive…which means not proved fully)

3.

Central premise would be: the absence of norepinephrine was required to enable the brain to remain asleep, while the absence of serotonin was necessary to allow dreaming to occur.

A)LSD does not cause as much long-term neurological damage as previously thought.( this somehow does not go with the context so I eliminated this option)
B) Serotonin and norepinephrine rise and fall in tandem.( which goes with the theory, both needs to be absent for dreaming)
C) Researchers prove conclusively that the level of norepinephrine in the brain is a significant factor in enabling the brain to sleep. ( yes it is as absence of this would only cause to sleep but in last passage it is given that there can be chances of person dreaming when awake when norepinephrine is accelerated and Serotonin is restrained but still it is a significant factor which very well goes with passage)
D) Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin.
E) The first four stages of sleep are as crucial to the process of dreaming as is the fifth stage. ( which is also fine)

rajcools · Answer

i took 7 minutes and got answers
b
c
b

but as per OA 3rd one is D

Ok B is also strong
but D it should be because in passage it is mentioned that LSD which inhibits serotonin induces dreams
so if we have a semi-hallucinogenic drug that induces hallucination(dreams while awake) without inhibiting serotonin then Jacob's central premise that amount of serotonin needs to be less for dreaming falls flat.

Yeah it was a toughie

francoimps · Answer

Explanation for #3:

"(D) Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin."

It may seem Out of Scope at first -- why would we bring in some other drug in the "argument." Tricky as it is, the answer choice actually implies that there are other hallucinogenic drugs other than LSD that still perform their main function--make one hallucinate--despite its inability to inhibit serotonin (unlike LSD).

Hence, if it is true that there are other drugs that make people hallucinate without inhibiting serotonin, then the whole argument of the author collapses since his underlying premise is that the inhibition of serotonin is a necessary condition.

Kurtosis · Answer

Explanation for Q5:

The second half of paragraph two discusses the stages of sleep, including stage 4.

(A) While it might be reasonable to assume that the four stages generally occur in order, the passage does not provide any information to infer that the fourth stage occurs only after passing through the first three.

(B) The passage states that parasomnias are “most common during stage 3”; the passage provides no information about whether parasomnias occur during stage 4.

(C) CORRECT. The fourth sentence of paragraph two says that the non-REM stages are not associated with normal dreaming. The fifth sentence then says that “the fourth stage, REM…is strongly associated with dreaming.”

(D) The passage does say that certain neurotransmitter levels “drop virtually to zero” during the fourth stage. The passage does not indicate, however, that the levels “fluctuate” (move up and down) during that stage.

(E) The passage says that the levels of the two neurotransmitters drop “when the brain is ready to enter the fourth stage.” This means the levels drop before the brain enters the fourth stage, not as a result of entering it.

Skywalker18 · Answer

1. According to the passage, which of the following is true of the drug lysergic acid diethlyamide?
A)Research into the drug is promising but inconclusive.
B)The neuron receptor sites that normally bind serotonin will also bind the drug.
C)The locus ceruleus causes the drug to affect bodily systems more rapidly than normal.
D)The drug stimulates norepinephrine and serotonin.
E)A person who ingests more than 20 micrograms of the drug will have hallucinations.

LSD mimics serotonin well enough to be able to bind at  most  of the neurotransmitter’s receptor sites, largely inhibiting normal transmission. -- 
As per option B , The neuron receptor sites that normally bind serotonin  will  also bind the drug. -- can we use WILL here ? The above statement in passage states that LSD mimics well enough to bind at most (NOT ALL) --> So , there will be some sites , in which LSD won't be able to bind . 
In my opinion, the usage of WILL in option B is incorrect.

AjiteshArun  ,  GMATNinja  ,  mikemcgarry  ,  egmat  ,  sayantanc2k ,  DmitryFarber  ,  MagooshExpert  , chetan2u  , other experts- please help

MagooshExpert · Answer

Hi Skywalker18 ! Happy to help

Here, I think we can interpret "sites" as referring to "some sites". For example, if we say: Ticks carry Lyme Disease. We aren't saying that ALL ticks carry Lyme Disease -- we are saying that ticks are able to carry Lyme Disease, and some ticks do carry Lyme Disease. This may not be the most precise language, but unfortunately it is very common. So here, that's what's going on -- when it says "receptor sites bind to LSD", that means "receptor sites are able to bind to LSD", and "some receptor sites do bind to LSD". I agree with you that the language is not very precise, and could be worded better, but again, it's something that you might run into, and should be aware of

Hope that helps! -Carolyn

jawele · Answer

1. According to the passage, which of the following is true of the drug lysergic acid diethlyamide?

(A) Research into the drug is promising but inconclusive. not into the drug but rather its effect in terms of dreaming

(B) The neuron receptor sites that normally bind serotonin will also bind the drug. " LSD mimics serotonin well enough to be able to bind at most of the neurotransmitter’s receptor sites, largely inhibiting normal transmission."

(C) The locus ceruleus causes the drug to affect bodily systems more rapidly than normal. the other way around": " In addition, the drug causes the locus ceruleus..."

(D) The drug stimulates norepinephrine and serotonin. the drug actually suppresses serotonin: "LSD mimics serotonin well enough to be able to bind at most of the neurotransmitter’s receptor sites, largely inhibiting normal transmission"

(E) A person who ingests more than 20 micrograms of the drug will have hallucinations. "will" is too strong as the passages mentions only "can"

2. Which of the following best represents the author's primary goal in writing the passage?

(A) to outline a theory and suggest options for further research options, no - a detailed theory is discussed and that it is yet inconclusive

(B) to act as an advocate for additional research to help elucidate a particular theory's validity "advocate" is too strong

(C) to introduce a theoretical construct that has not yet been sufficiently proven correct

(D) to demonstrate the complexities involved in conducting a certain type of scientific research this may be true, but if anything, "complexities" aren't the focus of the passage

(E) to articulate a hypothesis and lay out the case for proving it "proving" is wrong because the study is inconclusive

3. Which of the following, if true, would most undermine the central premise of the Jacobs hypothesis? The central idea: "The Jacobs hypothesis held that the absence of norepinephrine was required to enable the brain to remain asleep, while the absence of serotonin was necessary to allow dreaming to occur "

(A) LSD does not cause as much long-term neurological damage as previously thought. this is a clear outsider

(B) Serotonin and norepinephrine rise and fall in tandem. this would actually give more credence to the theory

(C) Researchers prove conclusively that the level of norepinephrine in the brain is a significant factor in enabling the brain to sleep. not sure about serotonine, but this would seem to go in line with the theory

(D) Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin. correct, since we would expect significantly reduce, if not remove, serotonine to allow dreaming and hallucinations

(E) The first four stages of sleep are as crucial to the process of dreaming as is the fifth stage. "fifth" is not given

4. According to the passage, all of the following are true EXCEPT

(A) Norepinephrine and serotonin are discharged only during waking states. correct: "Both neurotransmitters are discharged in high quantities only during waking states"

(B) Ingesting more than 20 micrograms of LSD will cause some people to hallucinate. "at doses higher than 20 micrograms, it can have a hallucinogenic effect"

(C) Rapid eye movement is the stage of sleep during which people dream. "At the onset of sleep,<...> the brain to enter the three non-rapid eye movement (non-REM) stages of sleep. <...> When the brain is ready to enter the fourth stage"

(D) LSD causes neurons to increase the rate at which they discharge norepinephrine. " the drug causes the locus ceruleus to greatly accelerate activity."

(E) The absence of serotonin seems to be necessary in order to enable the brain to dream. "The Jacobs hypothesis held that <...> the absence of serotonin was necessary to allow dreaming to occur

5. The passage implies which of the following about the fourth stage of sleep?

(A) One enters the fourth stage of sleep only after passing through the first three stages. "only" is a stretch

(B) Parasomnias, such as sleepwalking and confusional arousals, don’t occur during the fourth stage of sleep. "The non-REM stages typically are not associated with normal dreaming, though parasomnias, such as sleepwalking and confusional arousals, are most common during stage 3" so this leaves space to interpret that they may occur in other stages

(C) “Normal” dreaming occurs more frequently during the fourth stage of sleep than during the first three. correct: "The non-REM stages typically are not associated with normal dreaming <...> the fourth stage, REM, which is strongly associated with dreaming"

(D) Certain neurotransmitter levels fluctuate rapidly during the fourth stage of sleep. "certain" is ambiguous, and other transmitters aren't discussed in the passage

(E) Serotonin and norepinephrine drop as the result of the brain entering the fourth stage of sleep. the other way around: "the absence of norepinephrine was required to enable the brain to remain asleep, while the absence of serotonin was necessary to allow dreaming to occur"

I hope this will be helpful.

debojyoti25 · Answer

3:50 to Read

Around 1-1:30 to Solve

1. (A) Research into the drug is promising but inconclusive. --- The passage talks about the research of Jacob's theory and not LSD

(B) The neuron receptor sites that normally bind serotonin will also bind the drug. -- 3rd Para states this

(C) The locus ceruleus causes the drug to affect bodily systems more rapidly than normal. --The drug causes LC to discharge norepinephrine at a faster rate.

(D) The drug stimulates norepinephrine and serotonin. --Inhibits serotonin

(E) A person who ingests more than 20 micrograms of the drug will have hallucinations. -- Passage states "can" that doesn't mean the person will necessarily get hallucinated

2. 
(A) to outline a theory and suggest options for further research --- Nowhere in the passage the author is suggesting options

(B) to act as an advocate for additional research to help elucidate a particular theory's validity --- He is not advocating to elucidate, he says future scientific advances should allow this theory to be tested more rigorously

(C) to introduce a theoretical construct that has not yet been sufficiently proven -- The last line states this

(D) to demonstrate the complexities involved in conducting a certain type of scientific research -- Not in the passage

(E) to articulate a hypothesis and lay out the case for proving it -- He is not proving

3. Which of the following, if true, would most undermine the central premise of the Jacobs hypothesis?

(A) LSD does not cause as much long-term neurological damage as previously thought. --Out of scope

(B) Serotonin and norepinephrine rise and fall in tandem. --If Anything it strengthens the theory

(C) Researchers prove conclusively that the level of norepinephrine in the brain is a significant factor in enabling the brain to sleep. -- Option not enough convincing, merely states "level of norepinephrine in the brain is a significant factor rather than talking about decreasing levels"

(D) Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin.-- If true invalidates "recluding sleep, and inhibits serotonin, which Jacobs had postulated was a necessary condition for dreaming,"

(E) The first four stages of sleep are as crucial to the process of dreaming as is the fifth stage. ---OOS

4. According to the passage, all of the following are true EXCEPT

(A) Norepinephrine and serotonin are discharged only during waking states. --- Initially the passage states this but then goes on to mention that levels drop virtually to zero. -- ANS

(B) Ingesting more than 20 micrograms of LSD will cause some people to hallucinate.-- Passage states "can" that doesn't mean the person will necessarily get hallucinated . 1st Question Option e differs with this because of the word "some"

(C) Rapid eye movement is the stage of sleep during which people dream. --TRUE

(D) LSD causes neurons to increase the rate at which they discharge norepinephrine. -- TRUE

(E) The absence of serotonin seems to be necessary in order to enable the brain to dream.--TRUE

kabirgandhi · Answer

Great example of a high-level RC passage, complex read and a lot of trap answers.

Q2. Why did we choose C over B?

My guess is that C says that the author writes the passage to advocate for additional research (seems correct till now) to help elucidate a particular theory's validity (this makes it seem like the author is trying to prove the hypothesis correct) or is it because this choice is too narrow? (i.e., does not mention the purpose of the sleep-related concepts in the first 2 paragraphs?)

GMATNinja   MartyMurray   KarishmaB

egmat · Answer

kabirgandhi  The distinction between  (B)  and  (C)  is subtle, and it hinges on understanding the author's  tone  - a critical skill for Primary Purpose questions.

The Key Difference: "Advocate" vs. "Introduce"

The word  "advocate"  in choice  (B)  means to actively promote or champion something - it signals a persuasive, promotional tone. However, throughout this passage, the author maintains a  neutral, informative  tone. Look at the final sentence:

"The research thus far is promising but inconclusive; future scientific advances should allow this theory to be tested more rigorously."

This is an  observation  about what  could  happen, not a call to action or advocacy. The author isn't pushing for research; they're simply noting that the theory remains unproven and could be tested better in the future.

Choice  (C)  uses  "introduce"  - a neutral word that perfectly captures what the author does: presents Jacobs' theory, explains the supporting evidence, and notes it's "promising but inconclusive." The phrase "has not yet been sufficiently proven" directly aligns with that conclusion.

Your instinct was spot-on -  (B)  does make it seem like the author is trying to prove or promote the hypothesis, which doesn't match the passage's objective tone.

Regarding scope:  Both  (B)  and  (C)  are fine in terms of scope. The sleep-related concepts in paragraphs  1 - 2  serve to explain the theory, so they're implicitly covered by both "particular theory" and "theoretical construct." Scope isn't the issue that eliminates  (B) .

I hope this addresses your doubt.

rak08 · Answer

3. Which of the following, if true, would most undermine the central premise of the Jacobs hypothesis?

(A) LSD does not cause as much long-term neurological damage as previously thought.

(B) Serotonin and norepinephrine rise and fall in tandem.

(C) Researchers prove conclusively that the level of norepinephrine in the brain is a significant factor in enabling the brain to sleep.

(D) Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin.

(E) The first four stages of sleep are as crucial to the process of dreaming as is the fifth stage.

I dont disagree with option D as a fair answer choice but help me eliminate why not option B
if serotonin & norepinephrine rise & fall in tandem means they both increase & decrease together
if that happens serotonin cant be inhibited when norepinephrine increases so wont this undermine the hypothesis??

egmat   KarishmaB   GMATNinja

egmat · Answer

The Exact Central Premise:

The passage states that  "dreams and hallucinations share a common neurochemical mechanism"

Specifically:  Serotonin inhibition  is what creates the dream-like experience.

• Dreams → serotonin drops to zero → dream state
• LSD → inhibits serotonin → hallucinations (dreaming while awake)

---

Why (B) Doesn't Work:

(B) says serotonin and norepinephrine rise and fall in tandem.

But the passage  already tells us this  about normal sleep:

"Both neurotransmitters... drop virtually to zero"  during REM.

So (B) is  confirming  what happens during normal dreaming, not contradicting the claim that serotonin inhibition causes the dream-like state.

---

Simple Example:

Claim:  "Alcohol makes you drunk"

(B) is like saying:  "Alcohol and sugar always appear together in cocktails"
→ OK... but alcohol  still  makes you drunk.

(D) is like saying:  "Some people get drunk without consuming alcohol"
→  THIS  proves alcohol isn't necessary for getting drunk.

---

(B) doesn't challenge WHAT causes the effect. (D) does.

Answer: D

Scientific advances in the latter half of the twentieth century have

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GMAT Reading Comprehension (RC) Questions

Scientific advances in the latter half of the twentieth century have

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards