Evolutionary game theory — cooperation clusters vs defection
Cooperators
—
Defectors
—
Generation
0
■ Cooperate (C→C) ■ C→D next gen ■ Defect (D→D) ■ D→C next gen
Payoff matrix:
C vs C: R=1
C vs D: S=0
D vs C: T=b
D vs D: P=0
Each agent plays against 8 neighbors. At each generation, agents copy the strategy of their
highest-scoring neighbor (including themselves). Spatial structure enables cooperators
to form clusters that resist invasion — a key insight of Nowak & May (1992). Low temptation b
allows cooperation to survive; high b causes defection to sweep. Watch phase transitions at critical b ≈ 1.8.