Experimental Verification of Psychophysiological Index of Excitement

Abstract

There is a demand for the objective evaluation of emotion. Thus, ρ_min has previously been suggested as a psychophysiological excitement index to meet this demand in various applications. ρ_min is the minimum value of the cross-correlation coefficient between the respiratory sinus arrhythmia components of heart rate variability (HRV) and the respiratory wave, considering the lag time. In this study, the feasibility of using this index was verified in an experiment in which the ρ_min values of the physiological responses of individuals playing games, which were classified according to the level of difficulty, were analyzed. Three major results were obtained in the analyses. First, the ρ_min values of the responses changed significantly while playing the game. Second, the ρ_min values of the responses changed linearly with the game's level of difficulty, and the rank correlation was found to be significant. Finally, the variation in the ρ_min value corresponded with the subjects' self-reported excitement scores. The HR and indexes of the autonomic nerve activities were investigated simultaneously by means of the HRV spectrum; however, no change or correlation with the game's difficulty level was found. The feasibility of using ρ_min values as the psychophysiological index of excitement was therefore verified.