Primary and Secondary Task Analysis of Step Tracking: An Event-Related Potentials Approach

Abstract

The utility of the Event Related Brain Potential for the evaluation of task load was investigated. Subjects performed a discrete step tracking task with either first or second order control dynamics. In different conditions, the subject covertly counted auditory probes, visual probes, or tracking target steps presented in a Bernoulli series. In a fourth experimental condition subjects performed the primary tracking task without a secondary task. In the auditory condition, an increase in the difficulty of the primary task produced a decrease in the amplitude of the P300 elicited by the secondary count task. The introduction of the primary task in the visual condition resulted in an initial reduction in P300 amplitude but increasing task difficulty failed to attenuate the P300 further. A positive relationship between primary task difficulty and P300 amplitude was obtained in the step conditions. Furthermore, this effect did not require that the step changes be counted. The results are addressed in terms of the relative advantages of primary and secondary ERP workload assessment techniques.