Determinants of mental fatigue: The roles of cognitive control and dynamic difficulty adjustments: Proceedings of the 11th Meeting of the Expertise and Skill Acquisition Network

Introduction: Mental fatigue due to sustained engagement in cognitively demanding tasks can impair performance, yet understanding of its contributing factors remains limited. We developed computer-based protocols manipulating (a) cognitive-control load and (b) dynamic difficulty adjustments to examine their effects on fatigue development and task performance.
Methods: A between-subject multi-task experimental design (n = 72) compared (a) lower versus higher cognitive-control loads, and (b) higher cognitive-control load with fixed difficulty versus dynamic difficulty, where task speed adapted in real time to match fluctuations in performance. Task performance, subjective, and physiological fatigue indicators were assessed.
Results: Perceived fatigue increased over time across all conditions. Higher cognitive-control load impaired performance accuracy by 11% and slowed responses by 59% relative to lower load, accompanied by increased blink rate over time, indicating a decline in visual engagement. Dynamic difficulty adjustments sustained visual engagement, reduced accuracy by 24%, and accelerated responses by 20%, resulting in a 29% faster fatigue onset compared with fixed difficulty.
Conclusion: Both higher cognitive-control demands and dynamic difficulty adjustments contribute to mental fatigue and impair performance accuracy, with the latter promoting task engagement and accelerating fatigue onset. This study introduces a novel, time-efficient fatiguing protocol that reflects the dynamic demands of real-world high-performance activities. It also provides theoretical and practical guidance for applying engagement-focused strategies in skill acquisition to enhance effective learning while managing fatigue.