OG 2019 Verbal - CR: Weaken problems: Need help

Hi guys.
This is my first post and I hope I did post it in right place. I need help for 2 problems in Verbal OG.

I came across several CR problems in OG Verbal 2019, which I did not understand the explanations provided at the end of the section. Please help!!!

182. Psychologist: In a study, researchers gave 100 volunteers a psychological questionnaire designed to measure their self-esteem. The researchers then asked each volunteer to rate the strength of his or her own social skills. The volunteers with the highest levels of self-esteem consistently rated themselves as having much better social skills than did the volunteers with moderate levels. This suggests that attaining an exceptionally high level of self-esteem greatly improves one's social skill.

The psychologist's argument is most vulnerable to criticism on which of the following grounds?

Right answer: It overlooks the possibility that people with very high levels of self-esteem had may tend to have a less accurate perception of the strength of their own social skills than do people with moderate levels of self-esteem.

My answer: It takes for granted that the volunteers with the highest levels of self-esteem had better social skills than did the other volunteers, even before the former volunteers had attained their high levels of self-esteem.

Ok I understood why the right one is right, but why was mine wrong? My reasoning for the problem is that "The psychologist has concluded that high self-esteem leads to better social skills, they omitted the fact that self-esteem might resulted from good social life skills". And I found that my answer corresponds well to what I had thought.


186. To prevent a newly built dam on the Chiff River from blocking the route of fish migrating to breeding grounds upstream, the dam includes a fish pass, a mechanism designed to allow fish through the dam. Before the construction of the dam and fish pass, several thousand fish a day swam upriver during spawning season. But in the first season after the project's completion, only 300 per day made the journey. Clearly, the fish pass is defective.

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

Right answer: The construction of the dam stirred up potentially toxic river sediments that were carried downstream.
My answer: Fish that have migrated to the upstream breeding grounds do not return down the Chiff River again.

My reasoning for this problem is as following: The argument concludes that the defectiveness of the fish pass takes responsibility for decrease of fish passing through it. So any alternative cause of this decline in quantity of fish passing can weaken the argument. I saw that water intoxication causes thousand deaths of fish, and then decrease the number of fish swimming through the fish pass, but look at my answer, if the fishes who had successfully swam to the upstream didn't come back, so there can't be as many of fishes going through the dam this season as before. So this may also be considered as an alternative reason for the cutback of fish, then weaken the argument, right? Please show me where I got wrong way.