Evolving Cooperation

Active strategies:

Payoff: Mutual cooperation (R): 3

Payoff: Temptation defect (T): 5

Payoff: Sucker (S): 0

Payoff: Mutual defect (P): 1

Rounds per encounter: 5

Spatial structure (0=well-mixed): 0.7

PD condition: T > R > P > S (and 2R > T+S). In a well-mixed population, Defection dominates. Tit-for-Tat (Axelrod 1984 tournaments): cooperate first, then copy opponent. Spatial structure (Nowak & May 1992): cooperators cluster, resist defector invasion. Win-Stay Lose-Shift outperforms TFT in noisy environments. Evolution of cooperation requires: kin, reciprocity, network, group, or reputation mechanisms.