This paper researches and describes the effects of fatigue on cognitive performance, including the effects noted on persons in the aviation arena. The term, "fatigue," has yet to be defined in a concrete fashion. Fatigue, as addressed in human performance literature, refers to "deterioration in human performance, arising as a consequence of several potential factors, including sleepiness." Sleepiness, in contrast, has a more precise definition: "Sleepiness, according to an emerging consensus among sleep researchers and clinicians, is a basic physiological state (like) hunger or thirst. Deprivation or restriction of sleep increases sleepiness and as hunger or thirst is reversible by eating or drinking, respectively, sleep reverses sleepiness" (Akerstedt, T., Gillberg, M, 1990).
