Characterizing a user's mental involvement in interaction with complex systems

Complexity is only one of the many factors that influence the design of human interaction with complex systems, but it is extremely important. Depending on where and how it is instantiated and whether it is real or apparent, the user may perceive and deal with it differently. Successful user-system interaction becomes contingent on the user's capabilities and degree or extent of mental involvement. This paper presents a descriptive, five-variable model of that involvement. The model is then used to characterize three major types of interaction style: direct manipulation (DMI); virtual reality, the antithesis of DMI; and indirect, visualization-based interaction. Their respective strengths and weaknesses with regard to demands imposed on the user are hypothesized and discussed. The underlying theme is that adaptive HCI will require a designer's clear understanding of both the user-oriented and the system-oriented variables and distinctions.