Cooperation in social situations can be driven by self-interest, especially when the potential rewards increase. A study on the centipede game found that people's social preferences can be categorized into selfish, altruistic, or reciprocal groups. When playing a repeated centipede game with increasing final payoffs, individuals tend to cooperate more within groups of similar social preferences. This suggests that cooperation can stem from self-interested reciprocity, even in situations where it may seem altruistic.