Coding Effects on Performance in a Process Control Task with Uniparameter and Multiparameter Displays

Two experiments investigated the effectiveness of four methods for coding the operational states of targets in a process control task, under different levels of display density and inspection load, with search and identification tasks. In Experiment 1 subjects monitored one parameter (temperature) that could have four coded states. In Experiment 2 subjects monitored two parameters (temperature and oil level), each of which could have two coded states. Compared with partially redundant color coding or shape coding, color + shape coding and color coding led to quicker response time (RT) in a search task and mitigated the detrimental effects of increased display density. In addition, RT was faster with partially redundant color coding than with shape coding. Coding, however, had no effect on RT for the identification task. These findings held true across experiments. The effects of increased inspection load on RT were less pronounced with color + shape coding and color coding compared with the other coding conditions, but only when two parameters were monitored. Finally, RT was faster and responses were more accurate with one than with two parameters.