Punishing or helping: The influence of acute stress on third-party decision-making

In modern society, acute stress has become one of the main risk factors affecting human mental health and quality of life. Stress not only has a profound impact on the brain and cognition, but also affects human prosocial behaviors and social interactions. Acute stress has been implicated in modulating various social behaviors, including trust and empathy. However, it remains unclear how stress influences the third-party altruistic decision, especially in the face of conflicts between altruistic decisions and self-interest. When facing with a violation of justice, people show high probability of self-sacrifice to restore justice, but the optimal decision of the impact of stress on social decision-making in different circumstances is unclear. To address this question, we used a third-party intervention paradigm to assess participants' choice preferences after exposure to physical stress. In the third-party intervention task, participants could transfer MUs from their endowment to punish a norm violator or help the victim, and they could also leave the MUs to themselves. After the decision-making task was completed, participants were also asked to complete an analogous scenario task, including two crime scenarios: A robbery scenario and a traffic accident scenario. They were asked to put themselves in these situations and make calls as soon as possible based on priority, that is, call 110, the police, (i.e., punish offenders); call 120, the First Aid Center, (i.e., help victims); and call for themselves (i.e., defend their own interests). First, we found that selfish choices focused on the condition of fair offers. Second, compared with the moderate unfair condition, the serious unfair condition increased punishment and help behavior. Additionally, for the trade-off between the two prosocial choices under the condition of moderate unfairness, the participants in the stress group tended to increase the punishment behavior and reduce the help behavior, when compared with the control group. We also found that the increase of punishment behavior was not only reflected in the choice preference, but also in the intensity of punishment. The participants in the stress group punished more, consistent with the "fight or flight" pattern, which is considered to be the typical human response to stress. However, under the serious unfairness condition, there was no significant difference between the stress group and the non-stress group. In the scenario task, although there was no significant difference between the two groups in the three options, the stress group evaluated the accident scene to be more serious. These findings suggest that when the third-party helping and punishment as an optional prosocial behavior, stressed individuals are accustomed to choosing punishment behavior. This study provides evidence and explanations for studying the effects of stress on prosocial behavior.