Date of Award

Winter 2004

Document Type


Degree Name

Doctor of Philosophy (PhD)



Committee Director

Mark W. Scerbo

Committee Member

James P. Bliss

Committee Member

Peter J. Mikulka


Technological advances have allowed for widespread implementation of automation in complex systems. However, the increase in quantity and complexity of advanced automated systems has raised a number of potential concerns including degraded monitoring skills. The present investigation consisted of two studies that assessed the impact of system reliability, complacency potential, monitoring complexity, operator trust, and system experience on monitoring performance. In both studies, participants monitored a simulated aviation display for failures while operating a manually controlled flight task. In addition, the second experiment assessed the ability of operators to detect a single automation failure over three experimental sessions. Results indicated that realistic levels of system reliability severely impaired an operator's ability to monitor effectively. In addition, as system experience increased, operator performance for monitoring highly reliable systems continued to decline. Further, operators who reported higher levels of trust, confidence, and more frequent usage of automation demonstrated poorer overall monitoring. The complexity of the monitoring task was also shown to be one of the most important factors influencing operator monitoring performance with poorer performance on more cognitively demanding tasks that continued to degrade as system experience increased. Results from both studies indicated that operator trust increased as a function of increasing system reliability and that as trust increased, monitoring performance decreased. These results suggest that for highly reliable systems, increasing task complexity and extensive experience may severely impair an operator's ability to monitor for unanticipated system states.