Four studies evaluated the effects of shared and differential earnings on the choice between individual and partial-altruism contingencies. The experimental situation consisted of solving a puzzle on two synchronized computer screens. Thirty two college students were assigned to sixteen dyads, four in each experiment. Ex- periment 1 compared differential to non-differential exchange of points. Experiment 2 compared individual to shared administration of points under non-differential exchange. In Experiment 3, conditions were the same as in Experiment 2, but with differential exchange of points. Experiment 4 was like Experiment 3, but participants were located in separate rooms. Results showed that most dyads preferred to respond to the social contingency in which both participants were affected. However, sharing and differential exchange of earnings did not seem to affect choice. Verbal agreements within dyads, prior to solving the task, seem to be the common factor accounting for choice of the social contingency. Results are discussed in terms of the relationship between language and social behavior.