In this paper, the authors examine the question of whether a collective activity can influence cooperation in a subsequent repeated one-shot prisoner's dilemma (PD) game. They conduct two series of experiments. The first consists of control experiments in which 30 periods of a PD game are played, with a random rematching of the pairs in every period. In a second series of experiments, subjects first play a donation game (DG) and then the PD game. In the DG, they collectively discuss the amount of a donation to a given charity, before putting the question to an individual and anonymous vote. Cooperation levels in the PD games preceded by the DG are significantly lower than those observed in the control experiment.