Perceived harmony, similarity and cooperation in 2 × 2 games: An experimental study

Game harmony is a generic game property describing how conflictual or non-conflictual the interests of players are. Simple and general game harmony measures can predict mean cooperation in 2 × 2 games such as the Prisoner’s Dilemma, the Chicken and trust games. Two measures can be simply computed from monetary payoffs; another, the similarity index, can also be justified by theories of similarity-based reasoning. When data from Oxford and Frankfurt–Oder are disaggregated across experiments, countries and learning history, and when the similarity index is a valid measure, parsimonious regressions can explain around half of the variance in mean cooperation rates.