Two different types of mental fatigue produce different styles of task performance

Fatigue is a common symptom in modern society. To clarify the mechanisms underlying fatigue, we examined task performances and subjective scale scores associated with two different types of mental fatigue. The study group consisted of 20 healthy participants, who performed 0-back or 2-back test trials for 30 min as a fatigue-inducing task session. Just before and after the session, they completed advanced trail making test (ATMT) for 30 min and completed subjective scales to measure fatigue, sleepiness, and other factors. After the 0-back or 2-back task session, impairment of task performance was significant as assessed by increased error count in ATMT. In contrast, although task performance as assessed by mean reaction time during the 2-back task trials did not change over time, longer reaction time was observed over time during the 0-back task trials. After the 0-back task session, subjective levels of fatigue and sleepiness were increased; while after the 2-back task session, although subjective level of fatigue was increased, that of sleepiness was not altered. Two different types of mental fatigue produce different styles of task performance. We present a new conceptual hypothesis regarding the mechanism underlying the association between mental fatigue and task performance.