MASTOC is a replication of the Tragedy of the Commons by G. Hardin, programmed in NetLogo 4.0.4, based on behavioral game theory and Nash solution. It allows the simulation of socio-psychological dispositions of agents towards cooperative behavior, i.e. reciprocity, feelings of fairness, cooperativeness, conformity and risk aversion. Agent behavior is determined via Nash solution of a game biased by dispositions, using a nash calculation extension specifically programmed or NetLogo. NOTE: A version that does not require the Nash extension is now also online.