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: (i) framing, (ii) the number of players and (iii) the perceived risk of cooperating. We work with a (two-player) Prisoner’s Dilemma and with a three-player, two-strategy Public Good Game. 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. We find three strong effects (a) Framing; (b) The number of players (there is less cooperation in the three-person games that 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.