Models are approximations to objects or processes that maintain some essential aspects of the original.
In cognitive psychology, mental models are usually considered to be the ways in which people model processes.
The emphasis on process distinguishes mental models from other types of cognitive organizers such as schemas. Models of processes may be thought of as simple machines or transducers that combine or transform inputs to produce outputs.
While some discussions about mental models focus on the representation, the approach in this chapter considers mental models as the combination of a representation and the mechanisms associated with those representations.
A mental model synthesizes several steps of a process and organizes them as a unit. User models have parameters that can distinguish users. Sometimes these are set explicitly by the user and sometimes they are inferred by the computer from the user's past responses and behavior. In some user modeling techniques, users must create a profile of their interests. For example, in the information filtering technique known as selective dissemination of information, users must specify what terms match their interests.
However, users may not have a clear memory of preferences or may not want to give an honest response.