Motivation Science, Vol 12(4), Dec 2026, 454-465; doi:10.1037/mot0000430
In real-world settings, performing successive tasks of varying difficulty and motivational value often leads to cognitive fatigue. Although several theories address issues related to the direction or initiation of goal-directed behavior, extensions grounded on motivational intensity theory specifically predict effort intensity. According to motivational intensity theory, for tasks with known and fixed difficulty, effort increases proportionally with perceived difficulty, as long as success is possible and the required effort is justified by success importance. The present study examined whether avoidance instruction—designed to elevate the upper limit of potential motivation—could modulate the relationship between cognitive fatigue and effort. Participants completed a sequential-task paradigm while effort-related cardiovascular responses, specifically the preejection period, were recorded. Consistent with our hypotheses, following a prolonged fatigue-induction period, participants in the avoidance-instruction condition exhibited a significant physiological rebound, exerting higher effort and achieving superior performance on a subsequent difficult task. In contrast, participants without avoidance instruction showed a decline in effort. Crucially, subjective fatigue remained high across groups, suggesting that although cognitive fatigue inflates perceived task difficulty, it does not necessarily lead to disengagement. Instead, sufficiently potent motivational stimuli, such as avoidance-based instruction, can justify the high mobilization of resources required to perform despite prolonged cognitive engagement. (PsycInfo Database Record (c) 2026 APA, all rights reserved)