The lessons of the prisoner's dilemma suggest that cooperation based on self-interest is most likely to occur when the number of people involved is:
few but they interact frequently. few but they interact rarely. many but they interact frequently. many but they interact rarely.
A tit-for-tat strategy recommends that one always begin an interaction with another person by being:
nice, but retaliate if the other plays mean. nice and turn the other cheek if the other plays mean. mean, but be nice if the other plays nice. mean and stay mean—you have to stab others in the back before they stab you.
