Normally, the pineal gland governs a person's sleep-wake cycle by secreting melatonin in response to the daily cycle of light and darkness as detected by the eye. Nonetheless, many people who are totally blind due to lesions in the visual cortex of the brain easily maintain a 24-hour sleep-wake cycle. So the neural pathway by which the pineal gland receives information from the eye probably does not pass through the visual cortex.

For purposes of evaluating the argument it would be most useful to establish which of the following?

The argument: the pineal gland secretes hormones according to changes in light and dark. Blind people still react to normal sleep-wake cycle, therefore the pineal gland must not go through the visual cortex. We need an extra piece of information that will help us determine the soundness of the argument.

(A) Whether melatonin supplements help people who have difficulty maintaining a 24-hour sleep cycle to establish such a pattern

Here we are only dealing with people whose sight has not been impaired. In order to evaluate the argument, we need to understand how blind people's pineal glands react to changes in light.

(B) Whether the melatonin levels of most totally blind people who successfully maintain a 24-hour sleep-wake cycle change in response to changes in exposure to light and darkness

If the pineal gland is indeed responsible for mediating the sleep wake cycle, then blind people have to be responding to light and dark (that's how the pineal gland works). True, it is not via their visual cortex, but somehow the pineal gland of blind people must be able to detect light and darkness. Therefore (B) helps us determine that blind people do notice changes in light and darkness. If they didn't, then we could not conclusively say that the pineal gland is responsible for their ability to maintain sleepless, and we could not conclude that the pineal gland does not pass through the visual cortex.

(C) Whether melatonin is the only substance secreted by the pineal gland

This is tempting, but even if we find out that there is another substance that neither strengthens nor weakens the contention that the pineal gland bypasses the visual cortex.

(D) Whether most people who do not have a 24-hour sleep-wake cycle nevertheless have a cycle of consistent duration

Here the focus is shifted away from blind people and to those who do not have normal sleep wake cycle.

(E) Whether there are any people with normal vision whose melatonin levels respond abnormally to periods of light and darkness

Again, a shift away from blind people. That is we are trying to understand how the pineal glands of blind people work.


Tough question .
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Situation-

Daily cycle of ligth and darkness is detected by eye.Pineal gland maintains sleep wake cycle.The pineal gland secrets melatonin in response to this cycle of detection to maintain sleep wake cycle!
BUT blind people ( due to lesions in the visual cortex) also maintain the same rhythm or sleep wake cycle.

Conclusion-

So the neural pathway by which the pineal gland receives information from the eye probably does not pass through the visual cortex.

Evaluation-

The author is not sure about the mechanism.He has given us a PROBABLE explanation. We need to help him confirm or reject his conclusion.
We need to make it more probable or less probable.
We need to a help him find a piece of information that will help to find whether the neural pathway passes through visual cortex .

POE

(A) Whether melatonin supplements help people who have difficulty maintaining a 24-hour sleep cycle to establish such a pattern

We do not need to comfirm whether melatonin helps to maintain a 24 hour sleep wake cycle.We already know for a fact that melatonin does affect the sleep wake cycle.
Also the main point of the argument is about people who maintain normal sleep cycle.


(B) Whether the melatonin levels of most totally blind people who successfully maintain a 24-hour sleep-wake cycle change in response to changes in exposure to light and darkness

A yes answer to the above option will help confirm that pineal gland does respond to light and darkness cycles NOT detected by the eye.Hence, the neural pathway does not pass through the visual cortex.
A no answer to the above option will help confirm that the neural pathway does pass through the visual cortex.


(C) Whether melatonin is the only substance secreted by the pineal gland

That is besides the point. It may release many other substances but we are only interested in the melatonin and the associated mechanism.

(D) Whether most people who do not have a 24-hour sleep-wake cycle nevertheless have a cycle of consistent duration

The duration of the cycle is not so much of an issue as is the mechanism behind the sleep wake cycle.

(E) Whether there are any people with normal vision whose melatonin levels respond abnormally to periods of light and darkness

This does no help us understand the mechanism or the pathway behind the sleep cycle.The reasons for abnormal levels may be varied.
This option just tells us that melatonin levels change with light and darkness but does not answer whether the neural pathway passes through the visual cortex.


Hope the above helps!

I donot mind Kudos.

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Thank you expert for posting.
normally I prethink an assmption for evaluate question though in some easy cases, the prethinking process happens naturally without effort . When the prethinking process dose not happen naturally, we have to take effort to prethink.

when it is hard to prethink an assumption, we have a hard question. of course there are many other factore which make the cr questions hard.

I can not prethink assumption and I have to go to answer choices and take a very long time to get to correct answer.

how do you do this question to finish it in 2,3 minutes. ? do you prethink an assumption.

pls, I want to know what is the assumption you prethink. I do not want to know what is an assumption for the correct answer. it is easy to find an assumption for the correct answer after you find the correct answer. it is also easy to explain the correct answer. But the problem is how do you prethink an assumption and what is an assumption prethought for this type of question. all of us know that the prethough assumption maybe is not the assumption on which the weakener/strengthener is based but the prethinking process is alway helpful.

what did you prethink before you look at the answer choices for this question. How do you prethink for this question. that is what we want to learn from you. what do you do before you look at the answer choices.

we need to know the SPECIFIC goal which we need to find in the answer choices. what we need to find in the answer choices must be spedific for us to be successful.if we identify only the general goal such as "information which increase this conclusion" we can not succeed.

pls help.

Question is a classical example of shell game technique played in GMAT by test makers.
If we do little bit of pre thinking. We can hit the correcct answer.
Conclusion: Neyaral pathway for pineal gland transmission is not through visual cortex.

The assumption that the argument takes is :-
1. Even persons with proper vision , the neural pathway for pineal gland is not through visual cortex.
AND
2. Blind people maintain sleep wake cycle, do so by the secretion of pineal gland only.

So we need to find an answer choice that does both supports and weakens our assumption.

Contenders are A and B.
Lets got through option A:- It supports the fact that sleep wake cycle is maintained not by [b]Pineal gland[/b], but by supplements.
If we go to the basics of strengthen weaken questions, we will note that we cannot challenge the fact presented in the arguments, facts are always considered correct. It is the implication of the facts that needs to be targeted and hence...In the above question we must not stray away from the fact that sleep wake cycle is maintained by pineal gland.....
Refer to the question 122 OG 13 , In this question for weakening, we are not targeting the fact that outsourcing is not a profit making method, as it is fact stated in the argument.

http://www.manhattangmat.com/forums/out ... t8334.html

Option B : Clearly targets the assumption Blind people maintain the sleep wake cycle by secretion of penial gland.

Hope that helps!!!!!!!!!!!!!!!!!!!!!!

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Consider kudos, If my post helped!!!!!!!!!!!!!!!!!!!

1. Normal-Pineal gland releases melatonin in response to day and night
2. But wait, Blind people with lesions still mantain a consistent sleep cycle too
Conclusion: The pathway to get dark/light info from the eye skips the visual cortex
Key inferences/implications: 1. meltaonin regulates our sleep pattern in both blind and 'can see' people 2. Even in 'can see' people the pineal gland's pathway to producing melatonin skips the visual cortex

Pre-think- I see one possible and likely problem in this already, what if there was another way for the body to produce that melatonin consistently other than from light and darkness information?

Another important thing to notice that would have practical applications. None of the answer choices mention anything about a visual cortex, so even more justification not to not look to strengthen that link to any other part of the problem. Let's just focus on melatonin production then

A Meltaonin regulates sleep patterns. It's a fact in the prompt. We shouldn't doubt this which is what A is trying to do
B
C All we know about meltaonin is it regulates our sleep and is the only relevant hormone in the prompt. We could care less about other hormones OOS
D Prompt only talks about 24 hour sleep cycle OOS
E What does a spike or lack of meltanin have to do with anything? I'm not a scientist and this prompt doesn't tell me what an abundance or dearth of melatonin will do to my sleep cycle. We just want to know why a certain consistency of meltonin helps keep a regulated sleep pattern in both blind and 'can see' people

POE B

Let's look at B
(B) Whether the melatonin levels of most totally
blind people who successfully maintain a
24-hour sleep-wake cycle change in response to
changes in exposure to light and darkness

This question would answer the pre-think I had. If it is true that, say blind people can get means to produce meltatonin without detecting light, somehow regularly,they can still mantain a sleep cycle. Also agrees with prompt and constricts it to blind people and 24 hour sleep cycle. Doesn't make the errors of other answer choices.

hidden assumption is: Blind people are similar to normal people when it comes to melatonin secretion.

B: Correctly evaluates this assumption by gauging melatonin levels when blind are expose different conditions. If they are respond then they are similar to normal people.

My problem is the same as already mentioned above. I am pretty good at explaining answers I already know. Problem lies in the pre-thinking.

In this case, I have to support that the neural pathway by which the pineal gland receives information from the eye probably doesn't pass through the visual cortex.

My first answer was A. Because if I said the melatonin supplements helped people, it would mean that the pineal gland and melatonin did their job without the visual cortex or bypassing the visual cortex.

I am wrong somewhere in my thinking. I am convinced by option B. That is not a problem. Kindly help

yes, same concern here. If we are giving melatonin through supplements then melatonin certainly isn't passing through the visual cortex, and if it helps people in their sleep cycle then it is strengthening the argument and if doesn't help people in their sleep cycle then it is weakening the argument Imo! and so can be used to evaluate?
How isn't A the answer then?

Premise : normal person -> melatonin govern sleep - wake cycle. --> pineal gland
blind peopple : leison in visual cortex -> still have functioning sleep-wake cycle.

conclusion : ok, then visual cortex doesn't come in between of melotinin path.

Prethinking :

1> what if blind people develops different pathway then normal path of melotinin ? as it's given (in normal condition)


(A) Whether melatonin supplements help people who have difficulty maintaining a 24-hour sleep cycle to establish such a pattern => we can negate this as comparison is between normal and blind people. not anything about people who have difficulty in sleeping.

(B) Whether the melatonin levels of most totally blind people who successfully maintain a 24-hour sleep-wake cycle change in response to changes in exposure to light and darkness - so something changes in case of blind people, aligned with prethinking.

(C) Whether melatonin is the only substance secreted by the pineal gland - not relevant

(D) Whether most people who do not have a 24-hour sleep-wake cycle nevertheless have a cycle of consistent duration - not the point here.

(E) Whether there are any people with normal vision whose melatonin levels respond abnormally to periods of light and darkness - not the point here.

My reasoning was different so somebody pl approve :

Pineal grand => melatonin => visual cortex via. neural pathway => eye

normal cycle

No if in blind people with defect in visual cortex still getting the info of 24 hr sleep wake cycle then obviously visual cortex doesn't play any role. and cycle should be


Pineal grand => melatonin => eye

right?
But here the assumption is there is no other alternative thing for blind people working to make that happen.


(B) Whether the melatonin levels of most totally blind people who successfully maintain a 24-hour sleep-wake cycle change in response to changes in exposure to light and darkness

If this is true then yes, we can say neural pathway is not via visual cortex.
if not, then there is some other process and neural pathway could be via visual cortex

i found this CR quite easy.

All choices leaving B are out of scope.

And choice B is too easy to understand and tick for a correct answer.
a yes for B-means it passes thru visual cortex and a no- it doesn't.

Depending on the stage of Critical Reasoning, it is good to try to think like a test maker.

by P.O.E. process

a) Changes of m also change S-W cycle ------> This option doesn't tackle the connection urging for an explanation (L-D) captured by P.G. OUT!

c) P.G. produces element "X" ----> who guarantees this element is an alternate explanation for S-W cycle regulation? OUT!

d) Duration of S/W Cycle vary with/out eye -----> This option doesn't tackle the connection urging for an explanation (L-D) captured by P.G. OUT!

e) One element with eye varies melatonin abnormally regardless Light and Dark ---------> One single element can't be representative of a whole hypothesis This test could be helpful only if constantly we get this results from other individuals and if blind individuals also present the same result OUT!

The three reasons for why choosing B

1st) The main point of the hypothesis, which is the connection between Light-Darkness and P.G., is being fully assessed by the test. From the diagram below it is easy to see why this is the best option.

2nd) The test is being conducted in a controlled group (blind people), which would dismantle the hypothesis if proved the other way round. (the melatonin doesn't change in the abscence of an eye)

3rd) Differently from e), the question considers many individuals and not only one to be tested

Here is the logic.

Hope it helps

Well the key thing to notice here is the use of "many" in the stimulus and "most" in correct answer.

- "many" is not well define, and a relative term. hence it might not represent a big enough population to deduce a relationship (for exmaple x->y).

- Now the correct answer uses "most":

- assume that "most" do react. this means that:
51%-100% of the bling people eperiance relatiomship between light->Melatonin. this means we have a lrage enough population to claim that the relationship is real/strong/ didn't happend by a chance.

- assume the most did not react (but we still have "many":
- so 2%, for example, shows the relationship light->Melatonin. this means we might have too small of a sample population to deduce anything significat.

So we showed the B weakens & strengthens the conclusion.

Comment:
- the key thing to understand in this question is that the focus is not on the relationship between light->eyes->V.C->P.G->Mel ->Speel cycle.
- The focus is on the size of the population and weather it is big enough to decuce the mentioned relatioship.

This is an OG question.
Argument says that blind people who have lesions in visual cortex also maintain sleep-wake cycle.
Then what must be reason for this. Only B is questioning the melatonin level change in blind people.
So answer B.

Kudos are welcome.

Let's try variance test on choice B.

(B) Whether the melatonin levels of most totally blind people who successfully maintain a 24-hour sleep-wake cycle change in response to changes in exposure to light and darkness

The melatonin levels of MOST totally blind people......changes in exposure to light and darkness.

The conclusion falls apart.

The melatonin levels ...................do NOT change in exposure to light and darkness.
The conclusion stays.

This is the correct choice as when we take the two extremes, the conclusion is weakened and strengthened.

Hi Experts,
Can you help me to understand pre-thinking and underlying assumption to evaluate answer choices?
I tend to make statements in arguments causal to help bridge gap between premises and conclusion in order to find assumptions while attempting evaluate Q type.
For eg:
cause: variations in response to daily light as detected by eye
effect: PG gland governs person's sleep cycle by secreting M.
Final conclusion: NP by which PG receives information from eye does not pass through VC.
Supporting premise for conclusion: People who are totally blind due to defect in VC maintain 24 hours sleep cycle. This premise counters general principle in first sentence.
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adkikani, that is a very thorough analysis of the passage! As you've written, the author is saying that the eye detects the daily cycle of light and darkness and that the pineal gland secretes melatonin in response to that cycle. The author than cites the example of totally blind people who still maintain a 24-hour sleep-wake cycle despite having lesions in the visual cortex to conclude that the information sent from the eye to the pineal gland probably does not pass through the visual cortex (since the visual cortex has lesions and thus is most likely defective). This argument rests on the assumption that the sleep cycle of those totally blind people is dependent on the information from the eye, but what if that weren't the case? What if there was some other source of information regulating melatonin levels in those blind people? Or that the sleep cycles of those totally blind people were regulated by something other than melatonin? In that case, those blind people could maintain a 24-hour sleep-wake cycle even if the information from the eye does pass through the visual cortex (since, in that case, the information from the eye is not required). If the evidence suggested by choice B were established, we could better assess the validity of that assumption.

I hope that helps!
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Normally, the pineal gland governs a person's sleep-wake cycle by secreting melatonin in response to the daily cycle of light and darkness as detected by the eye. Nonetheless, many people who are totally blind due to lesions in the visual cortex of the brain easily maintain a 24-hour sleep-wake cycle. So the neural pathway by which the pineal gland receives information from the eye probably does not pass through the visual cortex.

What are we looking for - So, due to the lesions in the visual cortex , blind person can't detect the light , but still maintains the sleep and wake cycle. It is a fact that pineal gland secretes something to maintain the sleep/wake cycle. So we are thinking that pineal gland must have received the info of light/darkness by a way not via visual cortex (which is blocked in blind folks). So can we looking for details which can give us answer as yes / no.

For purposes of evaluating the argument it would be most useful to establish which of the following?

(A) Whether melatonin supplements help people who have difficulty maintaining a 24-hour sleep cycle to establish such a pattern
-- Irrelevant. We are not talking about supplements.

(B) Whether the melatonin levels of most totally blind people who successfully maintain a 24-hour sleep-wake cycle change in response to changes in exposure to light and darkness
-- If we say Yes - We can infer yes there must a way to pineal gland which doesn't go via visual cortex, which is blocked.
-- If we say No - We can infer there is no way. The only way is by pineal gland.This is the reason melatonin levels are not getting changed.There must be something else, which is controlling the sleep-wake cycle.
-- So this is the answer.

(C) Whether melatonin is the only substance secreted by the pineal gland
-- Even if there are other substances, there is no relation shown with sleep-wake cycle, so Irrelevant.

(D) Whether most people who do not have a 24-hour sleep-wake cycle nevertheless have a cycle of consistent duration
-- Irrelevant.

(E) Whether there are any people with normal vision whose melatonin levels respond abnormally to periods of light and darkness
-- There can be multiple reasons of this issue. Out of scope.

Question Type: Evaluate the Argument

Premise 1: Pineal gland secretes melatonin to govern the sleep wake cycle, based on the light & darkness as detected by the eye.

Premise 2: People who are blind due to lesions in visual cortex of the brain can maintain a 24 hour sleep wake cycle.

Conclusion: The neural path way through which the Pineal gland receives information, bypasses the visual cortex.

Analysis: We need to evaluate whether the conclusion that Pineal gland receives information from neural pathways that bypass the visual cortex. The Pineal gland governs sleep wake cycle by secretion of melatonin in response to light, hence a correct answer should evaluate this effect. Whether there are changes in melatonin levels of blind people, if YES then then conclusion is Incorrect, if NO then the conclusion is correct

Answer choice B, exactly asks the right question to evaluate the conclusion, if the answer YES, then Pineal gland does get information from the Visual cortex & if the answer is NO, then the Pineal gland receives information from a different mechanism than the visual cortex.



Thanks,
GyM
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