A novel approach to the physiological measurement of mental workload.

While performing a visuo-motor task under incrementally-varied levels of difficulty, individuals were probed with a variety of novel, task-irrelevant, auditory stimuli. To determine the effect of task load on cerebral-cortical processing of these stimuli, event-related potentials were recorded while participants performed the task. We found that N1, P2, P3 and late positive potential (LPP) component amplitudes were inversely related to task-difficulty. This suggests that a variant of the oddball paradigm - in which the stimulus stream comprises novel sounds - is capable of providing a reliable index of mental workload.