The relationship between task value, mental fatigue, and motivation: The role of trait mindfulness

Mental fatigue is the core sensation arising during mental effort investment. It has been claimed that it is impacted by valuation processes and influences motivation. However, there is a scarcity of studies examining the interplay between subjective value of the task, mental fatigue, and the motivation to invest effort. We addressed this issue in the present study. We also examined how trait mindfulness relates to these processes. In an online study, participants (N = 241) filled the FFMQ and performed tasks which engaged mental effort. Participants answered questions regarding the main dependent variables, i.e., mental fatigue, value of the task, and motivation to invest effort. The results of mediation analyses showed a consistent negative relation between the perceived value and mental fatigue, and a negative relation between mental fatigue and motivation to invest further effort. We have also shown that trait mindfulness is positively related to the perceived value of the task, which further relates to lesser fatigue and finally higher motivation to invest effort, however, the mediation path through value only is the strongest and most reliable one. Overall, our results inform the current debate on mental fatigue origins and provide insight into the relationship between trait mindfulness and motivational processes.