Human Systems Integration Division @ NASA Ames

Larkin and Simon's (1987) analysis of how graphical representations support task performance is applied to designing graphical displays that streamline information- processing tasks. Theoretically this streamlining is done by designing external data structures that (a) allow users to substitute less effortful visual operators for more effortful logical operators, and (b) reduce search for needed information. A design program called BOZ is used to produce four alternative displays of airline schedule information to support a task of making airline reservations. We postulate several procedures that use visual operators to perform the task using the different graphics. The number of times each operator is executed provides one measure of task difficulty (for a procedure and graphic). A second measure is the difficulty of executing each operator. Seven subjects performed the airline reservation task using each of the four graphics. Response times for the different graphics differ by a factor of two, which is statistically highly significant. Detailed data analyses suggest that these differences arise through substitution of visual operators for logical ones and through the use of visual cues that help reduce search. These analyses provide quantitative estimates of the time saved through operator substitutions.