Before revision:  We find that this simple extension of the game allows cooperation to flourish in well-mixed populations that adhere to either direct or indirect reciprocity. In combination with network reciprocity , however, the exit option is less conducive to cooperation.
After revision:  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.