The Potential for Misinterpretation Considered More Globally: A Response to Vicente and Ethier

We begin by considering the study by Bennett and Malek (this issue) in a broader context. Static mimic displays provide a domain perspective that is critical: the layout of system components, physical connections, and sensors. Existing display technology provides the ability to represent the flow of resources through a system dynamically. Not surprisingly, designers have attempted to exploit this capability (we have seen numerous examples in research laboratories as well as in the literature). We initiated a research program on animated mimic displays because we believed that these efforts had achieved only limited degrees of success and that a scientific approach would be required to produce a more effective format. The approach taken in this study has a parallel in the work performed by Cleveland and his colleagues (e.g., Cleveland, 1985), addressing the design of static graphs. They emphasize that the design of a graph involves making choices about the specific graphical features that are used to encode quantitative information. These choices, in turn, will require observers to perform specific elementary graphical-perception tasks to decode that information. From this perspective, effective display design involves choosing graphical features that can be decoded most effectively. The research in question has focused on a fundamental issue in the design of animated mimic displays: the evaluation of a number of graphical features (i.e., luminance and chromatic contrast, geometrical contours and borders, spatial and temporal frequency, and waveform) to assess their utility for encoding quantitative information. The graphical features responsible for more effective decoding (i.e., those producing effective apparent motion) were identified; the findings have been summarized in a set of design guidelines. Failures in visual decoding (i.e., bidirectional apparent motion) were also discovered and the graphical features responsible were identified. From the perspective of cognitive systems engineering (Rasmussen, Pjetersen, & Goodstein, 1994), these evaluations fall at the Boundary 1 level (controlled mental processes). We view this level of evaluation as necessary but insufficient. Evaluations at higher boundaries are needed as well (e.g., fault management). Vicente and Ethier (this issue) discuss a second set of fundamental issues that involve the mapping between these visual features and the domain properties to be represented. In Bennett and Malek, the term velocity was used to refer to physical properties of the display: the degrees of visual angle that a wave form moves during a unit of time (degrees/second). We do not use this term to refer to physical properties of the domain: how fast a fluid is flowing through a pipe (feethecond). Sensors in thermodynamic