The Influence of Respiratory Sinus Arrhythmia and Time of Day on Decision Making and Risk Taking

Abstract

Humans make a wide variety of decisions every day - from which route to take to the store to which job offer to accept. It has recently been proposed that two different systems, one affective and intuitive (System 1), the other logical and deliberative (System 2) interact to guide decision making. Neuroimaging research has supported this hypothesis, but other physiological indices of emotion regulation have been largely unexplored in the context of decision making. Respiratory Sinus Arrhythmia (RSA) is an index of cardiac vagal control, and has been shown to mediate emotion regulation, and vary under stress. Both impaired sleep and the phase of the sleep/wake circadian schedule also influence the expression and regulation of emotion. Sleep deprivation has been shown to lead to poor decision-making, but the relationship between sleep/wake circadian rhythms and decision making has been largely unexplored. Physiological indicators of emotion regulation (such as RSA) are likely to interact with sleep/wake circadian rhythms to influence the strategies used in decision making. The present study found that while time of day did not have an independent influence on decision making or risk taking, these functions appear to fluctuate with body temperature, a physiological index of circadian phase, with optimal performance occurring at higher body temperatures. Furthermore, while RSA appears to be unrelated to decision making and risk taking, circadian phase may influence physiological responses to stress (as measured by RSA) at different times of the day. In particular, morning-types may be more reactive to stress in the evening than during the day. Further research is needed to validate and clarify these findings.