ChrisLele wrote:
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 darknessIf 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 glandThis 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 durationHere 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 darknessAgain, 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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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.