Abstract
For mental stress assessments, we conduct basic research to determine the relationships between stress and time-variant biosignals fluctuation triggered by visual tasks (named trigger task). Our goal is to devise a suitable and quantitative index of mental stress for individual users based on an understanding of the fluctuation of time-variant signals of heart rate and respiration with their dependence on the trigger task. Experiments elucidate the relationships between subjective scores of mental stress (GHQ28) and an objective index derived from two biosignals, RR intervals of ECG and respiration signals, under a trigger task. The experiments use a visual search task and a maze task as the trigger task because the stress raised by these tasks can be controlled. The results show, except for a few non-sensitive subjects, a positive correlation between subjective score and biosignal index, which is LF/HF ratio of PCA score from both biosignals with small user dependency. We also clarify that the indices of the subjects whose GHQ28 score is under half are sensitive (in terms of stress) to the trigger task used. This paper demonstrates the possibility of quantitatively measuring mental stress by using the proposed biosignal index. In addition, for accurate stress measurement it is necessary that the trigger task suit the individual.
