On the largest lyapunov exponents of finger plethysmogram and heart rate under anxiety, fear, and relief states

We investigated the largest Lyapunov exponents (LLEs) of finger plethysmogram (FPG) and heart rate (HR) under anxiety, fear and relief states and compared each measured LLEs with the HR. We devised a task in which the participants experienced the emotions of anxiety, fear, and relief. FPG and HR were recorded during the task, and chaos analysis was applied to FPG to calculate the LLEs. Our results showed significant positive correlations between the LLEs of FPG and the degrees of anxiety and fear. In addition, the degree of relief showed a significant negative correlation with the LLEs of FPG. However, no significant correlation was observed between HR and the degrees of three emotions. These results suggest that the LLEs of FPG are a more sensitive psychological index than the HR.