Donald A. Norman
University of California, San Diego

One function of this chapter is to belabor the obvious; people's views of the
world, of themselves, of their own capabilities, and of the tasks that they are
asked to perform, or topics they are asked to learn, depend heavily on the
conceptualizations that they bring to the task. In interacting with the environ-
ment, with others, and with the artifacts of technology, people form internal,
mental models of themselves and of the things with which they are interacting.
These models provide predictive and explanatory power for understanding the
interaction. These statements hardly need be said, for they are consistent with all
that we have learned about cognitive processes and, within this book, represent
the major underlying conceptual theme. Nonetheless, it does not hurt to repeat
them and amplify them, for the scope of the implications of this view is larger
than one might think.

In the consideration of mental models we need really consider four different
things: the target system, the conceputal model of that target system, the user's
mental model of the target system, and the scientist's conceptualization of that
mental model. The system that the person is learning or using is, by definition,
the target system. A conceptual model is invented to provide an appropriate
representation of the target system, appropriate in the sense of being accurate,
consistent, and complete. Conceptual models are invented by teachers, design-
ers, scientists, and engineers.

Mental models are naturally evolving models. That is, through interaction
with a target system, people formulate mental models of that system. These
models need not be technically accurate (and usually are not), but they must be
functional. A person, through interaction with the system, will continue to modi-
fy the mental model in order to get to a workable result. Mental models will be

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