Chaotic Analysis of Finger Plethysmograms for Evaluation Emotion Induced by Exposure to Fragrance

Fragrance influences the psychophysiological state of a person; the volume of fingertip plethysmography is consequently affected by the aspiration of aroma. Further, it may be uncomfortable depending on the amount of odor that you inhales. In this study, to observe changes in emotions during aroma aspiration, the flow of scent was continuously directed into the nose of participants quantitatively and directly. Subsequently, the stimulation threshold during aroma inhalation and change in emotions were evaluated through a questionnaire and fingertip plethysmography. We developed a fragrance generator to ensure quantitative aroma flow and participants were asked to subjectively evaluate aroma intensity and the level of comfort in real time. The results confirmed the chaotic nature of the time series data of fingertip plethysmographs. Moreover, it was confirmed that the Largest Lyapunov Exponent (LLE), which provides an indication of the amount of fluctuation, corresponds to the subjective evaluation of comfort/discomfort. The value of the index decreases during pleasure and increases during discomfort. In other words, it was confirmed that the pulse wave fluctuated when the participants were experiencing discomfort.