Understanding the mental process and the decision that go around a user experience is important in getting the complete picture of the behaviour of the customer.
Within the analysis space of the UX research is a technique that really does focus on this aspect of understanding the model of how customers think.
The technique also has the added advantage that it can be used as a validation tool for interactions and information architecture.
There will be a workshop session demonstrating (quickly) how to do a mental model diagram.
Indi Young, Mental Models