In a recent study, one group of participants watched video recordings

In a recent study, one group of participants watched video recordings of themselves running on treadmills, and a second group watched recordings of other people running on treadmills. When contacted later, participants in the first group reported exercising, on average, 1 hour longer each day than did the other participants. This shows that watching a recording of yourself exercising can motivate you to exercise more.

Which one of the following, if true, most weakens the argument?

(A) In another study, people who watched recordings of themselves lifting weights exercised for more time each day than did people who watched recordings of themselves running.
(B) Another study's members exhibited an increased willingness to give to charity after hearing stories in which people with whom they identified did so.
(C) Participants who were already highly motivated to exercise did not report exercising for any longer each day than they had before the study.
(D) In studies of identical twins, participants who observed their twin reading overreported by a significant amount how much time they themselves spent reading in the days that followed.
(E) A third group of participants who watched recordings of themselves sitting on couches afterwards reported being sedentary for more time each day than did the other participants.

Let me take a shot at this question. The conclusion of the argument is "watching a recording of yourself exercising can motivate you to exercise more".
The evidence presented in support of the conclusion is that people who watched themselves in the video actually reported an 1 hour more on average.
We have a task to find a statement that weakens the conclusion.

Remember that we have to weaken the conclusion that watching a recording of yourself exercising does not necessarily motivate you to exercise more.

Option A : This choice just compares the set of people who watched themselves execise and who watched themselves lifting weights.Does not attach the conclusion in any way.
Option B : This choice somewhat strengthens the conclusion. It says that people donated to charity more after hearing stories with whom they identified.
Option C : This choice might seem to be an attractive one when you first read it. However,if you read it carefully,it does not attack the conclusion.
Option D : Here comes the answer. It says, that when a twin observed his/her twin reading, the former overreported. Now, think about our argument.May be, the people
who watched their own recordings overreported. In that case, the conclusion falls apart.
Option E : This choice again somewhat strengthens the argument.

Answer Option D looks like the only contender.

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OE please... OA provided not very convincing...

HI Harshgmat
appriciate to hear your reasoning why OA is not convingcing

Great Question!
Between C and D, C strengthens the argument. It can be inferred from C and the premise that people who were NOT highly motivated exercised longer each day, strengthening the conclusion - "watching a recording of yourself exercising can motivate you to exercise more."

D exploits the "When contacted later, participants in the first group reported " part of the premise. The participants themselves reported the results. D gives a reason that the conclusion is faulty.

(C) Participants who were already highly motivated to exercise did not report exercising for any longer each day than they had before the study.

(D) In studies of identical twins, participants who observed their twin reading over-reported by a significant amount how much time they themselves spent reading in the days that followed.

In my earlier attempt I has missed the subtle point in choice D- high-lighted above.

i.e. identical twin - So I am watching myself in the video and such persons have over reported.

So this destroys the argument that watching you own videos are doing exercise can motivate you.

Still I feel C is also weakener but D weakens the most.

LeoGT Thanks. Your post made me re-attempt....

The problem in C is that you do not know from which group the Participants quoted, were. Were they in the first? If so, the statement could weaken the argument. Were they in the second group (who saw others running on treadmills), then this statement strengthens the argument. Hence ruled out, in my opinion.

In a recent study, one group of participants watched video recordings of themselves running on treadmills, and a second group watched recordings of other people running on treadmills. When contacted later, participants in the first group reported exercising, on average, 1 hour longer each day than did the other participants. <==== premise

Conclusion: This shows that watching a recording of yourself exercising can motivate you to exercise more.

Which one of the following, if true, most weakens the argument?

(A) In another study, people who watched recordings of themselves lifting weights exercised for more time each day than did people who watched recordings of themselves running.
==> Similar phenomenon strengthens the conclusion.Eliminate A

(B) Another study's members exhibited an increased willingness to give to charity after hearing stories in which people with whom they identified did so.
===> Self identification causing similar act. This is Strengthening and not weakening. Eliminate B

(C) Participants who were already highly motivated to exercise did not report exercising for any longer each day than they had before the study.
===> Out of scope. Not related to conclusion. Eliminate C.

(D) In studies of identical twins, participants who observed their twin reading overreported by a significant amount how much time they themselves spent reading in the days that followed.
===> Ummmmm. Act looks similar but conclusion says reporting about the inflated results than actual. Looks good contender. let's keep this.

(E) A third group of participants who watched recordings of themselves sitting on couches afterwards reported being sedentary for more time each day than did the other participants.
===> Similar phenomenon. This actually is strengthening and NOT weakening. Eliminate E.

So by elimination method, we got correct answer choice 'D'.
Please Press kudos, if you liked the explanation .

In a recent study, one group of participants watched video recordings of themselves running on treadmills, and a second group watched recordings of other people running on treadmills. When contacted later, participants in the first group reported exercising, on average, 1 hour longer each day than did the other participants. This shows that watching a recording of yourself exercising can motivate you to exercise more.

In the question stem, we have the results of a study, and the conclusion related to these results.

Conclusion: This shows that watching a recording of yourself exercising can motivate you to exercise more.

Notice that as part of the study, participants self-reported their increase in exercise frequency. However, the conclusion states that this self-reported exercise frequency increase proves that participants actually did exercise more. Thus, a weakener might display a potential discrepancy between self-reported increase in exercise frequency and actual increase in exercise frequency.

Which one of the following, if true, most weakens the argument?

(A) In another study, people who watched recordings of themselves lifting weights exercised for more time each day than did people who watched recordings of themselves running.
This sort of strengthens the argument. It states that in a potentially similar study, participants actually did increase their exercise frequency.

(B) Another study's members exhibited an increased willingness to give to charity after hearing stories in which people with whom they identified did so.
There isn't much going on here. This answer discusses a study in which participants heard a story about someone else exhibiting another behaviour, and, in turn, their willingness to engage in that behaviour increased. Note that willingness to engage in a behaviour is similar to a self-reported increase in behaviour. This answer does not strengthen or weaken the conclusion.

(C) Participants who were already highly motivated to exercise did not report exercising for any longer each day than they had before the study.
This seems to be the "trap answer". It's important to note that even though some participants were not motivated to increase their exercise frequency, this does not mean that overall, participants did not actually increase their exercise frequency. Some participants may already be at some sort of peak level of performance. This does nothing to our conclusion.

(D) In studies of identical twins, participants who observed their twin reading overreported by a significant amount how much time they themselves spent reading in the days that followed.
Now we're getting somewhere. Here we have a study of two people who look identical and one observed the other doing an activity. The observing participant was found to have over reported his or her increase in frequency of the observed activity after observing his or her twin. This provides us a certain amount of evidence to doubt the conclusion that "watching a recording of yourself exercising can motivate you to exercise more". In the exercise study, participants self-reported their behaviour, and we require evidence to demonstrate that a self-report is not necessarily truthful. *I know that this answer seems farfetched, however, it truly is the best one out of all of the choices.

(E) A third group of participants who watched recordings of themselves sitting on couches afterwards reported being sedentary for more time each day than did the other participants.
This answer choice is really just demonstrating a study that is similar to the first study but studies a different behaviour. The results seem to be the same, thus, we cannot weaken our conclusion.

Options A, B, and E can be easily eliminated.

(C) Participants who were already highly motivated to exercise did not report exercising for any longer each day than they had before the study.

This option may induce us to think (incorrectly) that the second group was already motivated, so the experiment results are debatable.
However, read the conclusion again: This shows that watching a recording of yourself exercising can motivate you to exercise more.
Even if option C were true, it wouldn't WEAKEN the conclusion!

(D) In studies of identical twins, participants who observed their twin reading over reported by a significant amount how much time they themselves spent reading in the days that followed.

This option clearly tells us that looking at video of us (or a person similar to us) performing a task can induce us to overestimate the task actually performed. This clearly weakens the premise "When contacted later, participants in the first group reported exercising, on average, 1 hour longer each day than did the other participants. "

D is the winner!

D weakens nothing here. I suspected the correct answer, but I thought (and still think) reading has too little in common with exercising. Its harder to remember and measure how much we read than how much we exercise. 

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Great question. The main confusions is between C and D.

This is a cause-and-effect scenario. Argument states that if people watch a video of themselves exercising, they are motivated to exercise more daily. The objective is to weaken the argument.
From the premises, one word that should immediately stand out to you is 'self-report'.

Let's look at C and D:

(C) Participants who were already highly motivated to exercise did not report exercising for any longer each day than they had before the study.
- This isn't really affecting the argument. Who's motivated? Argument doesn't tell us. Could be more people motivated in Group A (video of themselves), or in Group B (Video of others), or equally distributed. We don't know. We could spin a story and justify this option, but this is a very very weak weakener at best.
I'd keep for now, in case the other options are worse.

(D) In studies of identical twins, participants who observed their twin reading overreported by a significant amount how much time they themselves spent reading in the days that followed.
- Now this directly attacks the argument. If a person observes their identical twin doing an activity and overreports his own time spent, then it provides a alternate explanation. Similarly, it may be the group seeing their own video exercising are overreporting the time spent and in reality work out the same number of hours.
We are attacking the link between the claimed cause-and-effect. X (seeing videos) may not cause Y (exercising more) because it could be Z (overreporting hours) instead.
Ans: D.

Bambi2021, in general for CR, don't bring in outside knowledge or assumptions. Need to be very focused on the logic and exactly what's stated. We can't assume people are more likely to misremember their hours spent reading. Eitherway, the crux of D isn't the activity itself but rather the idea of 'overreporting'. It's a common GMAT trap to make the wrong answer seem out-of-context, and to make the correct answer related to the question with similar words.

This is a really tough one to crack though it was one ina billioin cosmic fluke for me
A - gym lifting and runnning this was something i had to keep at last people are not pushing themselves but why compare to running when it was between individuals who watched and didn't watch themselves
B- out of the world charity no hope for this one
C - yes this was also a possible candidate however how can we relate to the passage if this people were present in both groups if average was taken
D- yes this could be reason all of this could be wrong if the entire this was overeportes i was so exicted after seeing this becoz i was only 2 options and none of this was never the option
E - the author ran out of options what had sleepiness has to do with what people had to do exercise which they committed and which was committed after the recordings
therefore IMO D hope all of this clears at least a bit of confusion

Bambi2021
ved02 has been crisp in his/her explanation to which i agree.
Here's what i think.
The problem with your reasoning is that you are focusing on wrong aspect of the argument just like i did. Reading or exercising doesn't matter, what matters is the logical build-up presented in the argument that must have been attacked by the right answer choice.
I too focused on wrong part - twins - by asking myself "Are we concerned about twins?". However, I did stuck up with the overreporting thing. Later i asked myself - Can't twins be the part of the group. What if they form the majority of the participants? Anyway, its obvious that C and D are the contenders in which C uses the keywords used in the argument, whereas D doesn't. In other words, C is deceiving that makes you choose it, if not paid attention rightly.

I also see that this question could have been reworded(just for fun) as
"Which one of the following, if true, is analogous/parallel to the reasoning presented in the argument?"
testing our analogy drawing reasoning ability. However, it's an anti-reasoning.

This is a tricky one because in the correct answer we need to infer that watching a recording of yourself is analogous to observing your twin.

This logic seems suspect to me -- I don't think this is something we would see on the GMAT.

On the other hand, C is the only other contender.

We can eliminate C because it tells us that participants who were already highly motivated to exercise did not report exercising for any longer each day than they had before the study. Were all the participants in this group (the group who were highly motivated)? Or were there unmotivated participants as well? We need to make further assumptions to make this choice work. Further assumptions always hurt the strength of the answer choice.

By process of elimination we can arrive at D.

Lets suppose after seeing our recording we get motivated and increases our exercise time but option D Create scenario homologous to oneself recording and we get significantly high (I. e more than 1 hour) therefore weaken the argument by saying that seeing ourselves increases more time than the claim

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