A Complexity Measure of Task Content in Information-Input Tasks

This article presents a measure of the task complexity a human operator faces while inputting information. The measure, called task-content complexity (TCC), depends only on the complexity of the task content. A human-computer information-transmission model is proposed to clarify task complexity. It is shown that the model has three hierarchical levels of task complexities: the computer device (hardware), the computer software, and the task content. The model provides a definition of task content and the concept of the TCC measure. It is theoretically proven that the TCC measure is related to the task content, and is independent of the computer system used. Experiments based on graphical information-input tasks confirm that the TCC measures of the same task using two different computer systems are almost equal. They also confirm the strong relationship between the TCC measure and the cognitive complexity of the task the operator performs. The TCC measure will be very useful in the design of computer tasks and in the evaluation and the usability rating of computer systems.