Passage Summary: Researchers found that people who watched videos of themselves working out said they exercised more later on than people who watched strangers, so they think self-videos are a great motivational tool.

Conclusion: Watching a video of yourself exercising can serve as a motivator to increase your actual exercise levels.

Reasoning: Participants who watched videos of themselves on a treadmill reported exercising an hour more per day than those who watched videos of strangers.

Analysis: To weaken this argument, we need to find a reason why the 'self-video' might not be the true cause of the extra exercise, or why the data itself is suspect. A major red flag here is that the exercise was 'reported' by the participants rather than measured objectively. Perhaps watching themselves made them feel more guilty or self-conscious, leading them to *claim* they exercised more to impress the researchers. Look for an answer that suggests the groups weren't comparable to begin with or that provides an alternative explanation for why the first group gave higher reports.