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# Scientific advances in the latter half of the twentieth

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Re: Scientific advances in the latter half of the twentieth [#permalink]

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27 May 2014, 00:01
Got all right and it took aroun 5-6minutes.

And it's a bit late but if this is helpful to any future students:
In Q 1, A is not right because the sentence (The research thus far is promising but inconclusive; future scientific advances should allow this theory to be tested more rigorously) that people are referring to actually means the whole research and not the research of the drug only.
In Q3, B is wrong beause the question is what would MOST hinder, not what would hinder. The right answer (D) would be the one that hinders the theory most.

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09 Jun 2014, 04:12
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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.
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Re: Scientific advances in the latter half of the twentieth [#permalink]

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11 Jun 2014, 05:08
Can anyone explain this phrase?

"LSD mimics serotonin well enough to be able to bind at most of the neurotransmitter’s receptor sites"

Is LSD binding neurotransmitter or...?
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11 Jun 2014, 06:33
pretzel wrote:
Can anyone explain this phrase?

"LSD mimics serotonin well enough to be able to bind at most of the neurotransmitter’s receptor sites"

Is LSD binding neurotransmitter or...?

In other words, the function of LSD is to act as a "fake" serotonin thereby blocking the so-called "receptor sites." Because of this, the "real" serotonin neurotransmitters are prevented from going to their receptor sites and consequently preventing them from functioning normally.
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18 Mar 2015, 09:19
Difficult passage. It must be from manhattan cats.
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16 Apr 2016, 13:22
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29 Apr 2016, 06:20
siddhans wrote:
Why is A wrong in 1?

The last line of the para says this:- The research thus far is promising but inconclusive; future scientific advances should allow this theory to be tested more rigorously.

I know my answer may not matter now to you, still I am happy to reply.
The passage does not intend to say that the research that seems promising was done on the drug rather the research was for the entire process.
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29 Aug 2016, 07:26
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8.40 mins
Q2:
P1: Hypothesis is introduced.
P3: Author asks for future research to test the validity of theory. "future scientific advances should allow this theory to be tested more rigorously."
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

Q3:
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.
....
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.
.......
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.”

D: Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin. //There are some medicine exception to J's hypothesis.
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Re: Scientific advances in the latter half of the twentieth [#permalink]

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05 Sep 2016, 09:38
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 [serotonin's] 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, [LSD] 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."
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24 Sep 2016, 03:47
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
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Scientific advances in the latter half of the twentieth [#permalink]

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31 Oct 2016, 21:59
The passage says LSD ................... bind .......the neurotransmitter’s receptor sites, whereas option B says the neuron receptor sites ........ bind serotonin will also bind the drug. Isn't it reverse? Moreover, how can we infer that receptor sites also bind drug?

I also don't understand why not it E.
The passage says 'at doses higher than 20 micrograms, it can have a hallucinogenic effect' which is in line of choice E.
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Re: Scientific advances in the latter half of the twentieth [#permalink]

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12 Dec 2016, 11:53
siddhans wrote:
Why is A wrong in 1?

The last line of the para says this:- The research thus far is promising but inconclusive; future scientific advances should allow this theory to be tested more rigorously.

he used the word promising which means second choice is better , which says he actually supports advocates the research being done
Re: Scientific advances in the latter half of the twentieth   [#permalink] 12 Dec 2016, 11:53

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# Scientific advances in the latter half of the twentieth

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