And yet They Tire: Cognitive Fatigue Facilitates Task Disengagement and Worsens Performance

Most scientists consider the ego depletion effect—worsened task performance after prior cognitive demand due to the exhaustion of a specific and limited resource—invalid. Yet, the negative effect of prior task engagement on self-control performance is a salient human experience. In the current study we aim to dissociate the effect of prior engagement on self-control performance from a limited resource account by applying recent advancements in fatigue literature to self-control empirically (the psychobiological model of endurance). The present study (N = 321) utilized understanding garnered from these recent advancements to overcome shortcomings in prior designs by (1) using an adaptive and longer (1h) fatigue induction and (2) the option to actively disengage from the main task in a dual-task design, allowing the theoretical influence prior task engagement has on motivation to influence performance through changes in persistence. Findings illustrated that participants that completed the fatigue induction protocol showed large post-induction differences in subjective fatigue (d = 0.83, BF10 > 1,000) and shorter persistence (d = -0.31, BF10 = 8.66), as well as lower performance (d = -0.31, BF10 = 9.21) in the main task, even when controlling for persistence differences, as compared to their control counterparts. Exploratory analysis further highlighted the predictive value of subjective post-induction fatigue and showed that performance is impaired, even when controlling for persistence. As suggested by recent findings in the fatigue literature, the present study supports the transition of self-control research away from a limited resource account and towards a perceived fatigue account.