Scientific advances in the latter half of the twentieth century have a

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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."