Is the perceived cost of effort influenced by the subjective sensation of fatigue?

Abstract

Mental fatigue has many repercussions on the everyday life of patients as well as healthy individuals. Mental fatigue is observed following prolonged cognitive activity. Our hypothesis is that the subjective reported mental fatigue has an influence on the perception of the cost of a task and thus influences behaviour. In this study, we used a modified version of the neuro-economical Westbrook N-back task to analyse participants’ behaviour: we asked them to make a choice between an easy and a difficult task, each with a different reward. Our results showed that, when faced with 2 options, subjects prefer the option with the lowest cost/benefit ratio: the harder the difficult option, the more likely subjects will choose the easy option, even if it has a smaller reward. To make comparisons of their behaviour between the fatigue and the control condition, participants started either with 2 hours of emotionally-neutral documentaries (control) or with a variant of the Stroop task (mental fatigue). We observed that mental fatigue alters the perception of mental effort cost but we could not show a significant difference in behaviour between control and fatigue sessions. We propose that this lack of effect could be due to the effort cost of the difficult option being too low compared to the reward. We consequently propose some improvements to the experimental procedure.Master [60] en kinésithérapie et réadaptation, Université catholique de Louvain, 201