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In-Depth Information
taken into account and the role of information reliability in a market-like simu-
lation scenario was addressed. Analogously, Giardini and colleagues [8] showed
that reputation was a means to punish untruthful informers
without bearing the
costs of further retaliation
, at the same time protecting the system from collaps-
ing. In addition, for certain percentages of cheating rates, in both studies, the
authors showed that reputation played a relevant role in enhancing the quality
of production in an artificial cluster of interacting firms.
3 The Model
Moving from the simulation framework developed in [4], we designed a simulation
platform in NetLogo in order to compare the performance of costly punishment
and reputation spreading in mixed populations in which different types of agents
play a Public Good Game (PGG), the classical experimental model used to
investigate social dilemmas [17]. In this game, agents decide whether to free-
ride or to contribute
1
a fixed amount (a contribution of 1 unit) to a public
pool. The sum of all the contributions is multiplied by a benefit factor (set
to 3 in the current model
2
) and the resulting quantity is divided amongst all
the participants in the group, without considering their contributions. This is a
classic public good where free-riding would be the utility maximizing strategy
at the individual level; however, if all agents adopted that strategy, this would
result in the overexploitation of resources and in a worse outcome at the group
level (the so-called
Tragedy of the Commons
[14]).
Algorithm 1.
Description of punisher's behaviors
for
Number of Timesteps
do
Random group formation of the population;
Agents take First Stage decision;
Gather and Distribution of the Public good in each group;
First Stage Decisions are made public within the group;
Agents make Second Stage decision;
Punishment Execution;
end for
Agents are either non-reactive or reactive types. In the former category we find
Cooperators
(C), who always contribute to the common pool, and
Free-riders
(FR), who never contribute to the common pool. Reactive agents change their
1
Note that the decision in this framework is binary whether to cooperate or not.
In other works, specially in those of experimental economics, this decision has to
be taken in a continuum, deciding how much to contribute from a total amount of
money common to all agents.
2
According to the game design, in order for contribution to be irrational for a utility-
maximizer individual, the tokens in the pot must be multiplied by an amount smaller
than the number of players and greater than 1.
