Abstract
Cooperation among unrelated individuals in social-dilemma-type situations is a key topic in social and biological sciences. It has been shown that, without suitable mechanisms, high levels of cooperation/contributions in repeated public goods games are not stable in the long run. Reputation, as a driver of indirect reciprocity, is often proposed as a mechanism that leads to cooperation. A simple and prominent reputation dynamic function through scoring: contributing behaviour increases one's score, non-contributing reduces it. Indeed, many experiments have established that scoring can sustain cooperation in two-player prisoner's dilemmas and donation games. However, these prior studies focused on pairwise interactions, with no experiment studying reputation mechanisms in more general group interactions. In this paper, we focus on groups and scores, proposing and testing several scoring rules that could apply to multi-player prisoners' dilemmas played in groups, which we test in a laboratory experiment. Results are unambiguously negative: we observe a steady decline of cooperation for every tested scoring mechanism. All scoring systems suffer from it in much the same way. We conclude that the positive results obtained by scoring in pairwise interactions do not apply to multi-player prisoner's dilemmas, and that alternative mechanisms are needed.
Highlights
Social dilemmas are situations where the optimal decision from the perspective of a self-interested individual conflicts with what is optimal for the group collectively
As we extend scoring mechanisms to group interactions more generally, and to multi-player prisoner’s dilemmas (PD) in particular, we increase the degree of freedom regarding the scoring rules that may apply
We observe a steady decline in cooperation; the decay occurs in much the same way, independent of the order in which the different treatments were played
Summary
Social dilemmas are situations where the optimal decision from the perspective of a self-interested individual conflicts with what is optimal for the group collectively. The common feature of these interactions is that in the absence of a suitable mechanism [6,7] and given insufficient foresight by the players [8,9], the only stable outcome coincides with the socially undesirable one, i.e. absence of cooperation.. Direct reciprocity assumes that a player would cooperate with another person expecting him to do the same in return [16]; under indirect reciprocity, instead, a person does not expect the recipient of his help to reciprocate, but he expects that someone else will [5]: ‘the recipients of an act of kindness are more likely to help in turn, even if the person who benefits from their generosity is somebody else’ [17]
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