This paper discusses the similarities and differences between cooperative learning and group contingencies. Cooperative learning refers to any methods in which students work together to help one another learn, while group contingencies refer to rewarding students based on the performance of a group. Research on the achievement effects of cooperative learning finds that these methods are effective primarily when they incorporate group contingencies, when groups are rewarded based on the average of their members' individual learning performances. The use of group contingencies within cooperative learning is hypothesized to motivate students to do a good job of explaining concepts and skills to their groupmates, and elaborated explanation is the principal behavior found to account for achievement gains in cooperative learning.