ABSTRACT
Fatigue can be decisively defined for physical materials because the resulting failure from fatigue is typically preceded by dislocations and deformations that can be observed with the proper tools. For humans, physical fatigue can also be indexed with physiological measurements, as first identified by A. Mosso. This chapter presents both performance effects and subjective ratings of fatigue as indicators of cognitive fatigue. Direct methods of measuring cognitive fatigue often involve examining patterns of performance over time on-task. Another method for assessing cognitive fatigue is to ask the individuals who are performing the task to report subjective feelings of fatigue. Based on a review of the literature on cognitive/mental fatigue, Ackerman identified three major factors associated with tasks that result in cognitive fatigue. The general consensus from models of cognitive fatigue and more general theories of attentional effort is that attentional effort represents personal resources that are available in some quantity which can be depleted through use.
