Basic research on measurement of mental work load utilizing physiological information

Various definitions and models have been proposed to evaluate mental work load, for example, task time analysis method and secondary task method based on single channel model. However, an evaluating method utilizing physiological information has been comparatively newly proposed. Therefore, this method has not been adequately examined with respect to its relation to be here to fore proposed methods and to its practical usefulness in evaluating mental work load. In this study comparison was made of various evaluating methods, i.e. task time analysis method, secondary task method, method utilizing physiological information, and subjective score method with emphasis on the method utilizing physiological information when a modeled experiment was conducted. In evaluating the regression by the experimental results, the adopted standard was time shared fraction (TSF), which was computed as the relative required time compared to actual permitted time based on the single channel model. The main results can be summarized as follows: (1) The evaluated TSF value is a useful index if it can be computed, because it reflects the individual ability of each subject, is proportional to the amount of given information, and is most faithful to the definition of single channel model. (2) The TSF value is significantly correlated to the value obtained by existing secondary task method and subjective score method. Thus, this result justifies the above mentioned (1). (3) In the adopted physiological indicators of this experiment, SRRP (skin resistance reflex pulse rate) has the strongest correlation to TSF value. Furthermore, this SRRP is relatively not affected by individual difference and is significantly correlated to subjective score and secondary task in the constant condition of atmospheric temperature and subject's arousal level and in the repetitive task.