Social exclusion decreases prosocial behavior.

TLDR

Seven experiments manipulated social exclusion by informing participants they would later be alone or that others had rejected them. Social exclusion substantially reduced prosocial behavior, causing lower donations, reduced willingness to volunteer, less helpfulness after mishaps, and decreased cooperation in mixed‑motive games; this effect was mediated by reduced empathy and persisted regardless of cost, recipient, or experimenter awareness.

Abstract

In 7 experiments, the authors manipulated social exclusion by telling people that they would end up alone later in life or that other participants had rejected them. Social exclusion caused a substantial reduction in prosocial behavior. Socially excluded people donated less money to a student fund, were unwilling to volunteer for further lab experiments, were less helpful after a mishap, and cooperated less in a mixed-motive game with another student. The results did not vary by cost to the self or by recipient of the help, and results remained significant when the experimenter was unaware of condition. The effect was mediated by feelings of empathy for another person but was not mediated by mood, state self-esteem, belongingness, trust, control, or self-awareness. The implication is that rejection temporarily interferes with emotional responses, thereby impairing the capacity for empathic understanding of others, and as a result, any inclination to help or cooperate with them is undermined.