Thus the Envision user interface design suggests a number of experimental studies. We have chosen these graphical devices because of their widespread use and expected power in communication, combined with the uncertainty of their actual impact. Using SuperCard, each trial presents a search results display captured from Envision. Each subject is asked to count the icons representing documents that meet given conditions, where the information about those conditions is graphically encoded in the display. Trials are divided between training and measured trials.
Objective measures are accuracy and time for task completion.
Subjects are also asked to rate each design point for cognitive difficulty and for desirability as an information source. Our studies are providing empirical evidence of the effectiveness of icon color, shape, and size in conveying both nominal and quantitative data. Because our quantitative measures are also widely used in formative usability evaluation while our qualitative measures are aimed solely at subjective measurement of usability, we expect to provide empirical evidence regarding the effectiveness of psychophysical foundations for designing information visualization displays. The resulting rankings of graphical devices will either confirm those suggested by other authors or support new rankings. Such rankings are fundamental to developing effective information visualization.