Now watch the laboratory

The five strategies above can play each other perfectly well without us. Below, every strategy meets every strategy — including itself — for a hundred and fifty rounds, three times over. Game theorists know them as Always Cooperate (Sunny), Always Defect (the Wall), Grim Trigger, Tit for Tat (Echo) and Generous Tit for Tat (Pal). Drag the slider to add trembling hands: a chance that any chosen move misfires. Noise is where strictness dies and forgiveness earns its keep.

Trembling hands 

ε = 3%