That typically is not going to matter, as only true believers are likely to buy in the first place, and any time one makes a change expecting to hear an improvement, one is likely to listen more intently than usual, and, of course, listening more intently means one is likely to hear more details, and so one may easily imagine that the change is causing one to hear more details, when it really is that one is listening more intently that causes the difference in noticing more details. So suckers reinforce their errors in such ways, becoming absolutely convinced that they themselves heard the difference, and no amount of reasonable discussion afterwards is likely to shift such a solidly imbedded prejudice. Words from disbelievers afterwards tend to just go in one ear and out the other, as they believe that they heard it for themselves.