0 someone who leaves a country, political party, etc., especially in order to join an opposing one: --
There was no way to know whether the defectors would fight for the opposition.
1 a person who leaves his or her own country or group to join an opposing one --
So the number of defectors will always increase and the population will eventually only consist of defectors.
Can punishment of defectors explain cooperation in social dilemmas?
Such defectors separate themselves from the body of the brethren.
These are just notations for expressing all possible combinations of contributors and defectors.
And second, they establish graduated enforcement mechanisms to allow potential defectors to learn about the costs of defection without being ostracized (at least, initially).
The initial success obtained by few defectors is quickly learned by the other agents, leading to lower and lower payoffs.
This is well illustrated in the case of night fishing being effectively restrained by kadakkodis endorsing fines and other punishments on defectors.
Cooperators cannot invade a population of defectors, since a single cooperator would see its payoff reduced to (near-)zero.