  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, in real life, reputations 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. Our
results show that low reputation works as a signal of untrustworthiness,
whereas medium or high reputation are not taken into account by participants
for orienting their choices. We also find that 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, we find that, when reputation is pivotal to selection, then a
substantial proportion of would-be-defectors turn into cooperators. Taken
together, these results provide insights on the characteristics of reputation
and on the way in which humans make use of it when selecting partners but also
when knowing that they will be selected.
