Effects of task difficulty and time-on-task on mental workload

Abstract

Twelve subjects performed a tracking task and a memory search task simultaneously on a computer screen. The dual task continued for approximately 10 min and was repeated three times, interrupted by a short break for subjective ratings: the NASA Task Load Index (NASA-TLX) and the Check List of Mental Condition. Event related potentials (ERP) evoked by the presentation of memory task stimuli were also recorded. All the subjects participated in three experimental sessions, which varied in difficulty of tracking task. Results demonstrated that the NASA-TLX and ERP were sensitive only to the change in task difficulty and were not affected by time-on-task or interaction between task difficulty and time-on-task.