Prisoner's dillema → a metaphor for the problems surrounding the evolution of cooperative behavior.
Consider only two kinds of players: those who allways cooperate and those who always defect.
Explore the consequences of placing these players in a two-dimensional spatial array.
Each player plays the game against each immediate neighbor, and after each site is occupied by the player (the owner or one of his neighbors) who score the highest total in the round.
Prisoner's Dillema standard form:
Two players which can choose either to cooperate (C) or defect (D) in any one encounter;
Both choose to cooperate → both get a pay-off of magnitude R;
DC or CD → D gets the game's biggest payoff T and C gets S;
Both choose to defect → both get P;
T > R > P > S.
Playing one time, D is better than C, but if playing in a sequence of encounters, D is unbeatable.