The nature and measurement methods of mental workload(MWL) for human cognitive activity at man-machine interface (MMI) were firstly discussed from the viewpoint of human information process model. Then, am model VDT experiment which simplifies the actual human-computer-interaction situation at MMI, was conducted for several subjects, where two subjects participated in experiment series and tried to solve the same cognitive task in competition. Adopted experimental parameters were (i) different kinds of cognitive task, and (ii) cycle time of information display, to see the influence on MWL characterisitics from psycho-physiological viewpoint. A special processing unit for eye camera was developed and used for measuring subjects¡Ç eye movement characterisitics.
Concerning data analysis, total number of display presentation until problem solving (ie., total information needed for problem solving) was assumed as anchoring objective measure for MWL, and the investigations were conducted from two aspects;(i)global interpretation on MWL characteristics seen in the subjects¡Ç behavior from viewpoint of human information process model, and (ii) applicability of MWL by means of biocybernetic method.
As regards to applicability of biocybernetic method, the nature of MWL characterisitics was first divided into two aspects: (i) efficiency of visual information acquisition, and (ii) difficulty of inner cognitive process to solve problem, both in time pressure situation. Then, the data analysis results for eye movement characterisitics were correlated to (i), while for heart rate characterisitics, (ii).