Cooperation without Memory or Space: Tags, Groups and the Prisoner's Dilemma

A Recent [14] model demonstrated that image scoring produces high cooperation between strangers in the Prisoner’s Dilemma (PD). Here we outline a simpler approach in which players – which are either pure cooperators or defectors – can sustain cooperation with strangers by biasing game interactions towards others with the same tags (arbitrary bit strings representing “cultural markers” [11]). In our model there is no requirement for knowledge of past performance or recognition of individual players. Unlike spatial models [13] reproduction of strategies is population wide. Contrary to previous tag models [15] cooperation is demonstrated in the single round game.