This research is concerned with the influence of fatigue on effort and associated cardiovascular (CV) responses in people confronted with challenges. The work assumes that behavior is sustained by energy and other performance resources that are temporarily depleted the longer and more vigorously people perform. The more resource-depleted (i.e., fatigued) people become with respect to a particular type of activity (e.g., math), the less capable they should feel in relation to relevant challenges (e.g., balancing a checkbook) and the more difficult those challenges should appear to be. Based on intuition, one might expect that perceptions of difficulty that result from fatigue would lead people to lower their effort and display reduced CV arousal as a result. However, a recent formal analysis of effort intensity suggests something different. Specifically, it suggests that the perceptions should have a different impact depending on (1) the difficulty of the challenge at hand, and (2) the importance of meeting that challenge. In theory, the key is whether fatigue causes people to move from a point of believing success is possible and worthwhile to a point of believing it is not. If difficulty and importance conditions are such that success appears possible and worthwhile to a non-fatigued group, but impossible or excessively difficult to a fatigued group, effort and associated CV responses should be greater in the non-fatigued group. The reason is because those in the non-fatigued group should exert the required amount of effort, whereas those in the fatigued group should withhold their effort. If difficulty and importance conditions are such that success seems possible and worthwhile to a fatigued group as well as to a non-fatigued group, effort and associated CV responses should be greater in the fatigued group. The reason in this case is because those in the fatigued group should have to exert extra effort to compensate for their relative lack of performance resources (i.e., for their fatigue). Finally, if difficulty and importance conditions are such that success appears impossible or excessively difficult to a non-fatigued group as well as to a fatigued group, effort and associated CV responses should be equivalent for the groups as they both should withhold effort. This somewhat counterintuitive perspective on fatigue influence is noteworthy in part because it offers insight into when fatigue should and should not impair performance in real world (e.g., education, work) settings. It also is noteworthy because it highlights a condition under which chronic fatigue may pose a health risk. Specifically, chronic fatigue may pose a health risk when it leads people to strive especially hard and, as a consequence, manifest exaggerated CV responses.
Five studies will be conducted over four years. The central purpose will be to evaluate the possibility that the influence of fatigue on effort and CV response to challenge varies depending on the difficulty and importance of success. It will be achieved by manipulating difficulty and importance variables and assessing the impact of those manipulations on responses of people who have been fatigued to different degrees. A further purpose of the studies will be to evaluate the idea that fatigue influence extends only to tasks relevant to the performance system that has been depleted. This will be achieved by assessing responses to tasks strongly and weakly related to the activity used to induce fatigue. To the degree that fatigue effects are task specific, they should be found only on the strongly related tasks. Because investigators have hypothesized recently that self-regulatory (i.e., restraint or inhibitory) activity may draw on a special performance resource that is not involved in sustaining other behavior, special attention will be devoted to comparing responses obtained in relation to tasks involving strong regulatory components with responses obtained in relation to tasks involving weak regulatory components.
