Detecting Defectors When They Have Incentives to Manipulate Their Impressions

  • Toko Kiyonari Aoyama Gakuin University
Keywords: cheater detection, cooperation, prisoner’s dilemma


We examined if naive observers can distinguish defectors from cooperators even when defectors may be motivated to present themselves positively. In Study 1, 150 participants played a “semi-sequential” Prisoner’s Dilemma Game (PDG) with real monetary incentives, half as first players and half as second players. First players decided to cooperate or defect, and second players made the same decision without knowing the first player’s choice. The first player was given a chance to present a video message to the second player before the latter made their decision. After the PDG, players played a separate one-shot, semi-sequential Stag Hunt Game (SHG), a coordination game where cooperation is the best choice insofar as the other also cooperates. In this game, the first player was not given a chance to send a video message. When the players had incentives to hide intentions or manipulate impressions of themselves, even motivated judges (whose monetary gain depended on the accuracy of cheater/cooperator detection) could not distinguish defectors from cooperators in either the PDG or SHG. However, they were able to discriminate “hard-core defectors” who defected in both games. In Study 2, however, in which judges had no monetary incentives to detect targets’ choices, participants were unable to discern even hard-core defectors. The contents of the messages did not provide help discerning defectors.