Permutation Entropy of the Heart Rate Reveals the Difference in Moral Judgment of Actions and Omissions

Recent research strongly supports the idea that cardiac activity is involved in the organization of social behavior and social cognition. The aim of this study was to explore the dynamics of heart rate irregularity, as measured by permutation entropy (PE), while individuals were making moral judgments about actions and omissions leading to serious physical harm to another person. The results have shown that participants (N = 58, 50% women, age 21–52 years old) judged harmful actions as less permissible than equivalently harmful omissions (phenomenon known as the “omission bias”). Importantly, the response times were significantly longer and PE values were higher when participants were evaluating harmful omissions, as compared to harmful actions. These results may be viewed as a psychophysiological manifestation of differences in causal attribution between actions and omissions, viewed by some authors as one of the bases for intuitive moral judgment. We discuss the obtained results from the positions of the system-evolutionary theory, which proposes that any behavior is based on co-operative activity of morphologically different cell groups distributed across the brain and the rest of the body that comprise functional systems. Thus, heart rate irregularity originates in co-operation of cardiovascular and other components of actualized functional systems, and reflects complexity of the dynamics of the organism-environment interactions, including their social aspects.