I will attempt to describe how human complexity, belief, and free-will impact the process from my perspective of an analyst. It is not an exaggeration to say the human component of a system will make or break the a system. It is the single overriding factor in determining success. On the other hand, if a solution is built while in continual dialog with its human interfaces so that the solution is also their solution, then it will matter little how good it is. They will make it work.
Several things are at play here.
What I have is my perception of the user's perception. Perceptions are fluid. They change over time and from person to person. One must stay engaged as the problem is a moving target. This is a human dimension.