Diagrammatic Displays for Engineered Systems: Effects on Human Performance in Interacting with Malfunctioning Systems

Computer graphics displays make it possible to display both the topological structure of a system in the form of a schematic diagram and information about its current state using color-coding and animation. Such displays should be especially valuable as user interfaces for decision support systems and expert systems for managing complex systems. This report describes three experiments on the cognitive aspects of such displays. Two experiments involved both fault diagnosis and system operation using a very simple artificial system; one involved a complex real system in a fault diagnosis task. The major factors of interest concerned the topological content of the display-principally, the extent to which the system structural relationships were visually explicit, and the availability and visual presentation of state information. Displays containing a topologically complete diagram presenting task-relevant state information at the corresponding point on the diagram appear to be superior to displays that violate these principles. A short set of guidelines for the design of such displays is listed.