Abstract
It is difficult for human operator to control complex and large system by hand, because the delay of system response could be long. Although some previous studies characterized the progress in the manual control from the view of the operator's performance, our previous study (Kobayashi et al., 2006) made the relation between the progress and the operator's mental activity clear based on background electroencephalogram (EEG). In this study, we tried to investigate the operator's mental activity when the control system is pitched into abnormal condition using the amplitude of theta waves (4-8Hz), and an experiment was conducted using a simulator. In this experiment, the background EEG was measured based on international 10-20 method while the subject controlled the on-screen target of the simulator. Participants were twelve male students ranging from nineteen to twenty-three years old. From the statistical result of their EEG data, we found that the amplitude of theta waves at frontal region was significantly high when they controlled the simulator under unexpected condition. Considering the relation between the results and the previous knowledge about theta waves, it was suggested that almost participants' concentration was getting higher because they tried to pay the attention to evaluating the abnormal system state. Consequently, an operator's cognitive process model under the unexpected system condition was represented through this study.
