Acute Social Stress Influences Moral Decision-Making Under Different Social Distances in Young Healthy Men

Acute social stress has been shown to influence social decision-making. This study aimed to examine how social distance modulates the influence of acute social stress on young male moral decision-making. Sixty healthy male college students were randomly divided to be exposed to the Trier Social Stress Test (TSST) or a placebo version of the TSST (P-TSST) before they performed moral decision-making tasks. The results showed that participants under acute social stress showed obvious increases in subjective stress perception, negative affect, salivary cortisol, and alpha-amylase and made more altruistic choices for others compared to the control group. However, social distance regulates the promotion of this acute social stress, with the promotion effect being stronger in socially distant others. Furthermore, the interpersonal order difference of different social distances in altruistic decisions is smaller in low-conflict dilemmas than in high-conflict dilemmas. In addition, an increase in salivary cortisol was positively correlated with altruistic choices toward both acquaintances and strangers, whereas an increase in salivary alpha-amylase was only positively correlated with altruistic choices toward friends. The results suggest that social distance modulates the promotion of acute social stress on moral decision-making, which might stem from the divergent effects of cortisol and alpha-amylase.