We investigated how differently people punish a free-rider in three experiments. Experiment 1 was conducted to examine how individual levels of trust and self-fairness influence their punishing behavior in a 5-person social dilemma. The results showed that trustful and unfair people, as well as distrustful and fair people, punish a free-rider more. To account for these results, we carried out a vignette-type study in Experiment 2, in which participants rated how likely they were to engage in a variety of punishing behaviors that typically happen in the real world. A factor analysis indicated that people usually assign two different types of meanings to punishing behaviors. One is "Vengeance," which unfair people, regardless of their levels of trust, tend to inflict; the other is "Warning," which tends to be favored by fair people. The results of Experiment 3, another vignette study, showed that observers also consider Vengeance as unfair and Warning fair. These findings imply that participants assigned one of the two meanings to their punishments in Experiment 1 depending on their levels of trust.
