It is believed that one of the principal effects of negative air ion is refreshing human psychological condition. Negative air ion can be observed in natural environments such as forest, fountain, and hot spring. In order to elucidate scientific reason of psychological effects by negative air ions, quantifying psychological effects will be important.
Healthy sixteen examinees (8 young candidates around 20 years, 8 old candidates around 60 years) are tested by SRS-18, blood pressure, questionnaire, and electroencephalogram. SRS-18, blood pressure, questionnaire was performed before and after experiment. Electroencephalogram was continuously measured during whole experiment and used for emotional spectrum analysis method (ESAM) calculation. Experiment was divided into three conditions (initial normal condition, negative air ion boosted condition at middle concentration, after ventilated condition) and three phases (accommodation, rest, calculation) at each condition.
At young group, excessive negative air ions increased human psychological concentration which is calculated by ESAM. At calculation phase, psychological concentration has a positive correlation with psychological stress (correlation factor 0.505). Otherwise at old aged group, no significant change was observed. It shows that sensitivity of negative air ions at old persons will be reduced. It also suggests that human sensitivity for negative air ion decreases with aging.
At rest phase of young group in negative air ion boosted condition, elementary emotions are balanced at ESAM. This shows that balancing among four elementary emotions is related with psychological effects of negative air ions.