The role of frames, numbers and risk in the frequency of cooperation

We report on a simple experiment that addresses three factors in the frequency of cooperation: (1) framing, (2) the number of players and (3) the perceived risk of cooperating. We work with a (two-player) Prisoner’s Dilemma and with a three-player, two-strategy Public Good Game. We also consider a payoff schedule isomorphic with the latter but in a nonsocial setup. These themes have been separately studied by a large number of experimental papers, using diverse methodologies. Our experiment targets them in a common, clear-cut framework that minimizes confusion. We find three strong effects (a) framing; (b) the number of players (there is less cooperation in the three-person games than in the two-person ones); (c) the neutralization of risk (about 50% of participants cooperate when risk is neutralized). Both (a) and (c) go in the expected direction, but, in all three cases, the strength of the effect is surprising. Cooperators appear to be more motivated by efficiency or by Kantian reasoning than by altruism.