Inference (Must be true)

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Inference (Must be true)

by neeti2711 » Sat May 27, 2017 7:49 am
Baking for winter holidays is tradition that may have a sound medical basis. In midwinter, when days are short, many people suffer from a specific type of seasonal depression caused by lack of sunlight. Carbohydrates, both sugars and starches, boost the brain's levels of serotonin, a neurotransmitter that improve the mood. In this respect, carbon hydrates act on the brain in the same way as some antidepressants. Thus, eating holiday cookies may provide an effective form of self-prescribed medication.

Which one of the following can be properly inferred from the passage?

(A) Seasonal depression is one of the most easily treated forms of depression.
(B) Lack of sunlight lowers the level of serotonin in the brain.
(C) People are more likely to be depressed in midwinter than at other times of the year.
(D) Some antidepressants act by changing the brain's level of serotonin.
(E) Raising the level of neurotransmitters in the brain effectively relieves depression.

OA: D
D says that some antidepressants act by CHANGING the brain's level of serotonin. The word CHANGING can be interpreted as either increasing or decreasing, so I believe, this option MUST not correct. Why not E?

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by DavidG@VeritasPrep » Sat May 27, 2017 8:20 am
neeti2711 wrote:Baking for winter holidays is tradition that may have a sound medical basis. In midwinter, when days are short, many people suffer from a specific type of seasonal depression caused by lack of sunlight. Carbohydrates, both sugars and starches, boost the brain's levels of serotonin, a neurotransmitter that improve the mood. In this respect, carbon hydrates act on the brain in the same way as some antidepressants. Thus, eating holiday cookies may provide an effective form of self-prescribed medication.

Which one of the following can be properly inferred from the passage?

(A) Seasonal depression is one of the most easily treated forms of depression.
(B) Lack of sunlight lowers the level of serotonin in the brain.
(C) People are more likely to be depressed in midwinter than at other times of the year.
(D) Some antidepressants act by changing the brain's level of serotonin.
(E) Raising the level of neurotransmitters in the brain effectively relieves depression.

OA: D
D says that some antidepressants act by CHANGING the brain's level of serotonin. The word CHANGING can be interpreted as either increasing or decreasing, so I believe, this option MUST not correct. Why not E?
Think of the following logical statements:

1) If x has increased then x has changed. This is a valid inference.An increase is a kind of change.

2) If x has changed then x has increased. This is not a valid inference. A change implies the possibility of a decrease.

This argument is an example of the first type of statement. We were told that neurotransmitter levels increased, so it's fair to infer that they've changed. You're thinking of the second scenario. So if, in the prompt, we were merely told that anti-depressants changed the level of neurotransmitters in the brain, then you would not have been able to infer that neurotransmitter levels had increased.
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by DavidG@VeritasPrep » Sat May 27, 2017 8:27 am
Why not E?
While anti-depressants increase serotonin, implying that higher serotonin levels are a good thing, it may not be the case that an increase in other neurotransmitters would help alleviate depression. Perhaps increasing, say, norepinephrine levels would actually make someone more depressed.
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