Critical Reasoning

A study followed a group of teenagers who had never smoked and tracked whether they took up smoking and how their mental health changed. After one year, the incidence of depression among those who had taken up smoking was four times as high as it was among those who had not. Since nicotine in cigarettes changes brain chemistry, perhaps thereby affecting mood, it is likely that smoking contributes to depression in teenagers.

Which of the following, if true, most strengthens the argument?

A. Participants who were depressed at the start of the study were no more likely to be smokers after one year than those who were not depressed.
B. The study did not distinguish between participants who smoked only occasionally and those who were heavy smokers.
C. Few, if any, of the participants in the study were friends or relatives of other participants.
D. Some participants entered and emerged from a period of depression within the year of the study.
E. The researchers did not track use of alcohol by the teenagers.

GMAT Kolaveri wrote:A study followed a group of teenagers who had never smoked and tracked whether they took up smoking and how their mental health changed. After one year, the incidence of depression among those who had taken up smoking was four times as high as it was among those who had not. Since nicotine in cigarettes changes brain chemistry, perhaps thereby affecting mood, it is likely that smoking contributes to depression in teenagers.

Which of the following, if true, most strengthens the argument?

A. Participants who were depressed at the start of the study were no more likely to be smokers after one year than those who were not depressed.
B. The study did not distinguish between participants who smoked only occasionally and those who were heavy smokers.
C. Few, if any, of the participants in the study were friends or relatives of other participants.
D. Some participants entered and emerged from a period of depression within the year of the study.
E. The researchers did not track use of alcohol by the teenagers.

This CR concludes that X causes Y: that smoking CAUSES depression.

One way to WEAKEN this type of CR is to show that the causal relationship actually works IN REVERSE: that Y (in this case, depression) causes X (in this case, smoking).

Answer choice A: Participants who were depressed at the start of the study WERE NO MORE LIKELY TO BE SMOKERS after one year than those who were not depressed.
This answer choice RULES OUT the possibility that depression causes smoking.
By ruling out this possibility, answer choice A STRENGTHENS the conclusion that smoking causes depression.

The correct answer is A.

The correct answer is A.

This can be easily achieved through elimination of the other options which are very out of context.

A shows that depression does not cause smoking and that only the converse is true.

Hence, A!

The Q shared is very educative.
See, there are 5 five ways to strengthen an argument in cause-effect relationship:-
1.There are no other causes to the effect than the cause mentioned.
2.the reverse i.e the effect doesn't cause the "cause". ( Applicable to this Q)
3.when cause is not present the effect is also not present.
4. when the effect is not present the cause is also not present.
5. the facts that support the cause-effect relationship, are true/valid/without any loop-holes.

I'm certain that these points will help you.

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