Partner selection supported by opaque reputation promotes cooperative behavior

Reputation plays a major role in human societies, and it has been proposed as an explanation for the evolution of cooperation. While the majority of previous studies equates reputation with a transparent and complete history of players' past decisions, reputations in real life are often ambiguous and opaque. Using web-based experiments, we explore the extent to which opaque reputation works in isolating defectors, with and without partner selection opportunities. We found that low reputation works as a signal of untrustworthiness, whereas medium or high reputations are not taken into account by subjects for orienting their choices. Reputation without partner selection does not promote cooperative behavior; that is, defectors do not turn into cooperators only for the sake of getting a positive reputation. Finally, in a third study, when reputation is pivotal to selection, then a substantial proportion of would-be-defectors turn into cooperators. Taken together, these results provide insights about the characteristics of reputation and about the way in which humans make use of it when selecting partners, and also when knowing that they will be selected.