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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Christopher Lele
Magoosh Test Prep

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.

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.
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