People's bodies respond to foods, medications, and the rest of the environment in ways very relative to how their bodies work. In a similar vein, people's minds digest information relative to the way their minds work. What one really wants, and what compels someone is probably the most fundamental psychological force to be considered. Basically, people see and hear what they want to hear. Not that there isn't an external force playing along.
There have been times I leaped to a dreadful conclusion and realized that some part of me willed that assumption to take hold of me. I backtracked and did some hardcore introspection as to why I would want that.