The designer has an obligation to provide an appropriate conceptual model for the way that the device works. It doesn't have to completely accurate but it has to be sufficiently accurate that it will help in both the learning of the operation and also dealing with novel situations.
Donald A. NormanBehavioral design is all about feeling in control. Includes: usability, understanding, but also the feel.
Donald A. NormanAlso note that invariably when we design something that can be used by those with disabilities, we often make it better for everyone
Donald A. Norman