Moderate cardiac vagal tone predicts more cooperation in highly sensitive individuals.

Cooperation, as a mutual collaboration, is a defining feature of human social life. Individual characteristics can influence cooperation. Recent studies have shown a quadratic relationship between cardiac vagal tone (CVT), an index of self‐regulation, and prosocial behaviors. Individual differences in cooperation might also vary as a function of people's environmental sensitivity (ES), i.e., may be influenced by individual differences in the perception and processing of inner and external stimuli. We tested the direct and interactive effect of CVT and ES on cooperative behaviors in two independent samples. We measured heart rate and engagement in cooperative acts in 80 young adults (M = 23.61; SD = 1.60) who were also asked to self‐report on ES. We found an inverted‐U relationship between CVT and cooperative behaviors. ES, on the other hand, did not predict differences in cooperative behaviors but moderated the relationships between CVT and cooperation, although the magnitude of this result was small. Specifically, only among individuals with higher ES cooperative behaviors change as a function of CVT. Highly sensitive individuals with lower or higher CVT, were less cooperative than low sensitive ones. Subsequently, we replicated the same study design in a second sample of 88 undergraduate students (M = 23.69; SD = 4.91). Once again, we found evidence supporting the presence of an inverted‐U relationship between CVT and cooperative behaviors, and we also found that ES moderated the relationships between the quadratic CVT term and cooperation. Our findings add new evidence on physiological self‐regulation as an underlying mechanism of prosocial behaviors, in particular cooperation. In two independent samples, our results showed a quadratic relationship between cardiac vagal tone (CVT) and cooperation. We found that this relationship is moderated by environmental sensitivity (ES). Specifically, only among individuals with higher ES, cooperative behaviors change as a function of CVT. To make the world more cooperative, people should learn how to regulate especially when they are highly sensitive. [ABSTRACT FROM AUTHOR]