ABSTRACT
This chapter aims to provide the assumptions: that fatigue is a real process, identifiable; that its impact on behavior is distinctive, and separable from those of other states; and that it has a central representation. The work–fatigue hypothesis – the need to identify the factors that cause fatigue and evaluate the assumed link between fatigue and work. The interpretation of fatigue as a factor in motivational control is based on its hypothesized role as a marker of cognitive conflict or discomfort. The relation between fatigue and energy – the need to understand the role of brain energy transformations in the fatigue process. Motivational control aspects of fatigue – the need to consider the alternative role of fatigue as an adaptive process helping to regulate goal-directed activity. Varieties of fatigue – the need to address the similarities, differences and connections between different types of fatigue: mental, physical, sleepiness.
