Complexity of heart rate variability during moral judgement of actions and omissions

Abstract

Recent research strongly supports the idea that cardiac activity is involved in the organisation of behaviour, including social behaviour and social cognition. The aim of this work was to explore the complexity of heart rate variability, as measured by permutation entropy, while individuals were making moral judgements about harmful actions and omissions. Participants (N = 58, 50% women, age 21-52 years old) were presented with a set of moral dilemmas describing situations when sacrificing one person resulted in saving five other people. In line with previous studies, our participants consistently judged harmful actions as less permissible than equivalently harmful omissions (phenomenon known as the "omission bias"). Importantly, the response times were significantly longer and permutation entropy of the heart rate was 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. We discuss the obtained results from the positions of the system-evolutionary theory and propose that heart rate variability reflects complexity of the dynamics of neurovisceral activity within the organism-environment interactions, including their social aspects. This complexity can be described in terms of entropy and our work demonstrates the potential of permutation entropy as a tool of analyzing heart rate variability in relation to current behaviour and observed cognitive processes.

Keywords: Clinical psychology; Complexity; Functional systems; Heart rate variability; Moral judgement; Neurovisceral integration; Permutation entropy; Psychology; Social cognition.

Figure 1

Experimental procedure. Participants answered a set of questions about their general health and recent intake of food, liquids and drugs. Then they were explained the details of the experimental procedure and given instructions. After filling a demographic questionnaire, participants were presented with a moral dilemma task containing 30 moral scenarios, which contrasted harmful actions and omissions, harms intended as the means to a goal and harms foreseen as the side effect of a goal, as well as harms involving physical contact and harms without physical contact. Heart rate was recorded throughout the duration of the experiment. Heart rate complexity was analyzed for Action, Omission, Means, Side effect, Contact and No contact trials.

Figure 2

Comparisons between Action vs Omission, Means vs Side effect, and Contact vs No contact trials: (a) Responses to moral dilemmas given as permissibility ratings of harmful actions and omissions on a scale from 1 = ‘Forbidden’ to 7 = ‘Obligatory’; (b) Response times in ms, from presentation of a moral scenario to giving a response by pressing the ‘next’ key; (c) Median value of the last 15 RR-intervals prior to a response; and (d) PE values calculated for sequences of the last 15 RR-intervals prior to a response. Paired-samples t-tests, ∗∗p < 0.01, ∗∗∗p < 0.001; Wilcoxon matched pairs tests, exact ^{# #}p < 0.01, ^{# # #}p < 0.001.