Abstract
Quantitative measures of consistency are formulated for human-computer interactive tasks. Two different kinds of consistency are considered: cognitive consistency and display layout consistency. Cognitive consistency is formulated by constructing the methods used for a task and the steps needed to perform the methods. A quantitative value for cognitive consistency is determined by analyzing the number of changes which would have to be made to change one method to another method. Display layout consistency is formulated by examining display parameters between two or more layouts. An experiment was performed to test the predictions of the quantitative analyses of consistency. Cognitive inconsistent tasks and inconsistent display layouts had a slightly detrimental effect on the speed of performance during an initial session. When the subjects had to return to the task several days after originally learning the task, performance on the cognitive inconsistent tasks was slower than on inconsistent display layout tasks. This latter result indicates that users will not necessarily have difficulty when learning inconsistent interactive methods but the problem will occur once the methods are learned and the user must switch between programs using inconsistent methods of interaction.
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