4 research outputs found
Clustering in large networks does not promote upstream reciprocity
Upstream reciprocity (also called generalized reciprocity) is a putative
mechanism for cooperation in social dilemma situations with which players help
others when they are helped by somebody else. It is a type of indirect
reciprocity. Although upstream reciprocity is often observed in experiments,
most theories suggest that it is operative only when players form short cycles
such as triangles, implying a small population size, or when it is combined
with other mechanisms that promote cooperation on their own. An expectation is
that real social networks, which are known to be full of triangles and other
short cycles, may accommodate upstream reciprocity. In this study, I extend the
upstream reciprocity game proposed for a directed cycle by Boyd and Richerson
to the case of general networks. The model is not evolutionary and concerns the
conditions under which the unanimity of cooperative players is a Nash
equilibrium. I show that an abundance of triangles or other short cycles in a
network does little to promote upstream reciprocity. Cooperation is less likely
for a larger population size even if triangles are abundant in the network. In
addition, in contrast to the results for evolutionary social dilemma games on
networks, scale-free networks lead to less cooperation than networks with a
homogeneous degree distribution.Comment: 5 figure
Evolution of cooperation driven by zealots
Recent experimental results with humans involved in social dilemma games
suggest that cooperation may be a contagious phenomenon and that the selection
pressure operating on evolutionary dynamics (i.e., mimicry) is relatively weak.
I propose an evolutionary dynamics model that links these experimental findings
and evolution of cooperation. By assuming a small fraction of (imperfect)
zealous cooperators, I show that a large fraction of cooperation emerges in
evolutionary dynamics of social dilemma games. Even if defection is more
lucrative than cooperation for most individuals, they often mimic cooperation
of fellows unless the selection pressure is very strong. Then, zealous
cooperators can transform the population to be even fully cooperative under
standard evolutionary dynamics.Comment: 5 figure
Transient nature of cooperation by pay-it-forward reciprocity
Humans often forward kindness received from others to strangers, a phenomenon called the upstream or pay-it-forward indirect reciprocity. Some field observations and laboratory experiments found evidence of pay-it-forward reciprocity in which chains of cooperative acts persist in social dilemma situations. Theoretically, however, cooperation based on pay-it-forward reciprocity is not sustainable. We carried out laboratory experiments of a pay-it-forward indirect reciprocity game (i.e., chained gift-giving game) on a large scale in terms of group size and time. We found that cooperation consistent with pay-it-forward reciprocity occurred only in a first few decisions per participant and that cooperation originated from inherent pro-sociality of individuals. In contrast, the same groups of participants showed persisting chains of cooperation in a different indirect reciprocity game in which participants earned reputation by cooperating. Our experimental results suggest that pay-it-forward reciprocity is transient and disappears when a person makes decisions repeatedly, whereas the reputation-based reciprocity is stable in the same situation
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Reputation Effects in Public and Private Interactions
We study the evolution of cooperation in a model of indirect reciprocity where people interact in public and private situations. Public interactions have a high chance to be observed by others and always affect reputation. Private interactions have a lower chance to be observed and only occasionally affect reputation. We explore all second order social norms and study conditions for evolutionary stability of action rules. We observe the competition between âhonestâ and âhypocriticalâ strategies. The former cooperate both in public and in private. The later cooperate in public, where many others are watching, but try to get away with defection in private situations. The hypocritical idea is that in private situations it does not pay-off to cooperate, because there is a good chance that nobody will notice it. We find simple and intuitive conditions for the evolution of honest strategies