The Event Related Cortical Potential as an Index of Task Workload

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Abstract
This paper describes an investigation which assessed the feasibility of the event related brain potential (ERP) to provide an index of operator workload in adaptive man-machine systems. The characteristics and requirements of such systems are described and some limitations of secondary task workload measures enumerated. The results of an experiment are then presented in which ERPs were recorded from 10 subjects, while the difficulty of a concurrent tracking task was varied. Subjects performed either a one or a two dimensional compensatory tracking task, while ERP's were elicited by presenting discrete auditory stimuli. The amplitude of the P300 complex, a component of the ERP, elicited by the stimuli, decreased from the control condition (no tracking) to the tracking conditions. An ERP based measure of sequential processing of the stimuli was further affected as tracking difficulty was increased from 1 to 2 dimensions. An algorithm for obtaining an on-line ERP based measure of workload is then described.