Experiments with N-Person Social Traps II

Abstract

A version of the Tragedy of the Commons was played by 16 four-person groups, 2 three-person groups, and 1 two-person group. Calculation of individually rational equilibria for the seven-round game was out of the question. The collectively rational strategy, on the other hand, is salient: No one is to draw from the common resource pool for the first six rounds, allowing the pool to double each round; then each is to claim an equal share of the pool, which has increasedby by a factor of 64. The game was presented under two conditions: minimal and full instructions, the latter including the disclosure of the collectively rational strategy. None of the four-person groups and neither of the two three-person groups achieved the optimal result. Only the single two-person group cooperated all the way, refraining from drawing from the pool until the last round and harvesting $38.40 on the final round. This pair was given the full instructions. Full instructions did have a positive effect, however, raising the level of cooperation as measured by several indices.