The interaction resembles a repeated PD because people are cheating the experimenter :D The ending effect happens all the time in experiments. If people play t

The interaction resembles a repeated PD because people are cheating the experimenter :D The ending effect happens all the time in experiments. If people play the repeated prisoner's dilemma, they'd cooperate UNTIL the last round. If people play the public good game, they'd contribute generously UNTIL the last round. Because if the prioner's dilemma and public good game are played one shot, the rational thing to do is to cheat right away (defect / not contribute). Being cooperative (in hope to make the world a better place) goes against the selfish motives. So, at the last round, because there is no tomorrow, it's just like the game is played one-shot, people'd cheat. The theory of game goes too far to say that, if people are rational, they work the game backward (backward induction) and at the 9th round, they'd cheat, and at the 8th round, they'd cheat...-> they'd cheat right from the first round. But experiments show that people are myopic or at least dont cheat right in the first round, they wait until last round. Because of experiments, theorists have to add the social image. Social image can be built in the first 9 round, but in the last round, not anymore.