  We study the evolutionary dynamics of the prisoner's dilemma game in which
cooperators and defectors interact with another actor type called exiters.
Rather than being exploited by defectors, exiters exit the game in favour of a
small payoff. We find that this simple extension of the game allows cooperation
to flourish in well-mixed populations when iterations or reputation are added.
In networked populations, however, the exit option is less conducive to
cooperation. Instead, it enables the coexistence of cooperators, defectors, and
exiters through cyclic dominance. Other outcomes are also possible as the exit
payoff increases or the network structure changes, including network-wide
oscillations in actor abundances that may cause the extinction of exiters and
the domination of defectors, although game parameters should favour exiting.
The complex dynamics that emerges in the wake of a simple option to exit the
game implies that nuances matter even if our analyses are restricted to
incentives for rational behaviour.
