Date of Award

Winter 2007

Document Type


Degree Name

Doctor of Philosophy (PhD)



Committee Director

James Bliss

Committee Member

Barbara Winstead

Committee Member

Shannon Bowling


Military operations routinely require military personnel to consistently perform their duties over several hours or days. Tasks that require prolonged work can lead to mental fatigue and decreased performance. The transactional model proposes that individuals cope with changes in the environment and maintain performance. This ability to cope is determined by factors of the environment and the individual's personality. One environmental factor that can influence coping is extended task performance. This study examined the effect of extended task performance and its interaction with task difficulty. Participants interacted with the military simulation game Command and Conquer: Generals™ for three hours. They were assigned to either the easy or difficult level of the game. Extended task performance led to an increase in feelings of fatigue. However, it also led to a decrease in mental workload. Contradictory findings were found for situation awareness. Performance on the item measuring perception decreased while performance on items measuring prediction increased. Participants' game performance increased in that they killed more opposers and lost less of their own troops over time. Participants in the difficult group experienced more fatigue than those in the easy group. Task difficulty had no significant interaction with time spent on the task. This study extends current knowledge by providing evidence for the effect of time-on-task fatigue in relation to mental workload, situation awareness, and performance. The use of a computer simulation game, Command and Conquer: Generals™ provides an opportunity to examine the effect of extended task performance in an interactive environment. Providing quantifiable data about when and to what extent time-on-task fatigue influences performance can provide a framework for additional training measures. Additionally, the data collected implicate that performance can improve over time; particularly if the task is continuous, participants have past experience with it, and are motivated to continue performing the task.


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