gasilvac> It is one of my main objectives to model a population that
gasilvac> can be characterized in principle by its three behavior
gasilvac> strategies enabling their members to imitate adaptive
gasilvac> behavior in their successive interaction. These strategies
gasilvac> can be so described: 1. Cooperative individuals always ready
gasilvac> to cooperate with those members they interact with, provided
gasilvac> they interact with other cooperators, they will benefit from
gasilvac> this interaction. 2. Defectors or individuals that never
gasilvac> cooperate with those they interact with, always intent on
gasilvac> exploiting their partners. 3. Punishers or individuals that
gasilvac> rather than cooperating they punish those they cooperate
gasilvac> with, provided they can be described as defectors in previous
gasilvac> encounters. In acting like this, they have to invest some
gasilvac> sort of resources whenever a defective behavior takes place.
In the NetLogo Models Library, look under
Social Science -> Unverified -> Prisoner's Dilemma -> PD N-Person Iterated.