COEXISTENCE OF COOPERATION AND DEFECTION IN PUBLIC GOODS GAMES

The production of public goods by the contribution of individual volunteers is a social dilemma because an individual that does not volunteer can benefit from the public good produced by the contributions of others. Therefore it is generally believed that public goods can be produced only in the pre...

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Bibliographic Details
Published in:Evolution 2011-04, Vol.65 (4), p.1140-1148
Main Authors: Archetti, Marco, Scheuring, István
Format: Article
Language:English
Subjects:
Cooperation
Cooperative Behavior
Evolution
Evolutionary biology
Game Theory
Group size
Humans
Linear transformations
mixed equilibrium
Models, Psychological
prisoner's dilemma
Prisoners
Prisoners dilemma
Public good
Public goods
Step functions
volunteer's dilemma
Volunteerism
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Summary:The production of public goods by the contribution of individual volunteers is a social dilemma because an individual that does not volunteer can benefit from the public good produced by the contributions of others. Therefore it is generally believed that public goods can be produced only in the presence of repeated interactions (which allow reciprocation, reputation effects and punishment) or relatedness (kin selection). Cooperation, however, often occurs in the absence of iterations and relatedness. We show that when the production of a public good is a Volunteer's Dilemma, in which a fixed number of cooperators is necessary to produce the public good, cooperators and defectors persist in a mixed equilibrium, without iterations and without relatedness. This mixed equilibrium is absent in the N-person Prisoner's Dilemma, in which the public good is a linear function of the individual contributions. We also show that the Prisoner's Dilemma and the Volunteer's Dilemma are the two opposite extremes of a general public goods game, and that all intermediate cases can have a mixed equilibrium like the Volunteer's Dilemma. The coexistence of cooperators and defectors, therefore, is a typical outcome of most social dilemmas, which requires neither relatedness nor iterations.
ISSN:0014-3820
1558-5646
DOI:10.1111/j.1558-5646.2010.01185.x