ASSESSMENT OF MENTAL WORKLOAD WITH TASK-IRRELEVANT AUDITORY PROBES

A study was performed to examine the utility of an ERP-based irrelevan t probe technique for the assessment of variations in mental workload. Ten highly trained Navy radar operators performed a simulated radar-m onitoring task which varied in the density and type of targets to be d etected and identified. This task was performed in the presence of a s eries of irrelevant auditory probes which the radar operators were ins tructed to ignore. Prior to performing the radar-monitoring task the s ubjects performed a block of auditory detection trials in which they w ere asked to respond to the occurrence of one of two low probability t ones and ignore the other low probability tone along with a higher pro bability standard tone. ERPs were recorded from the occurrence of the tones in both the baseline and low and high workload radar-monitoring conditions. The amplitude of the N100, N200, and early and late mismat ch negativity (MMN) components decreased from the baseline to the low load radar-monitoring task and again with an increase in the difficult y of the radar-monitoring task. P300 amplitude was sensitive only to t he introduction of the radar-monitoring task. These results are interp reted with respect to the phenomenon of attentional capture and sugges t that the ERP-based irrelevant-probe technique might prove an effecti ve method for the nonintrusive evaluation of increases in mental workl oad in complex tasks.