Perceived fatigue does not alter effort-based decision making but does undermine confidence in the ability to perform physical actions

Abstract

Fatigue may affect the decision to deploy effort (cost) for a given rewarded outcome (benefit). However, it remains unclear whether these fatigue-associated changes can be attributed to simply feeling fatigued. To investigate this question, twenty-two healthy males made a series of choices between two rewarded options: a fixed, no effort option, where no physical effort was required to obtain a set, low reward vs. a variable, effortful option, in which both the physical effort requirements (i.e. different durations of a sustained contraction performed in the lower limbs) and rewards (i.e. greater monetary incentives) was varied. Effort-based choices were made under two conditions: (1) a rested (control) state, (2) a pre-induced state of perceived fatigue, evoked through physical exertion in the upper-limbs, thus controlling for the physical manifestation of fatigue (i.e. decline in muscular force production in the lower limbs) on the decision process. Though prior physical exertion increased the perception of fatigue, participants choices did not significantly differ between control and fatigue conditions. Across both conditions, participants demonstrated an anticipated aversion to effort, with greater effort requirements reducing the decision to engage in actions associated with higher rewards. However, in the fatigue state only, decision time was prolonged and self-reported confidence in individuals’ ability to perform high effort actions was reduced. The findings suggest that a perceived state of fatigue does not necessarily alter cost/benefit comparisons within effort-based decisions, but may introduce greater uncertainty within choice and reduce self-confidence. These findings evidence altered evaluative processes during decision making under conditions of fatigue.