In this experiment you are a part of a group of players. In every game you will be asked to decide if you cooperate or do not cooperate with the group. If the group succeeds, every member of the group gets a bonus. If the group fails, every member of the group pays a cost. The probability of success is proportional to the number of cooperating members (that is, the more members choose to cooperate, the bigger the probability of group success is). Nevertheless, cooperation has a cost that you have to pay in order to cooperate.

Before deciding whether to cooperate or not, you may declare your presence to the group. Players do not know the number of players in the group, but they are informed how many players chose to declare their presence. The declaration of presence has no cost.

Before deciding whether to cooperate or not, you may declare your presence to the group. Players do not know the number of players in the group, but they are informed how many players chose to declare their presence. The declaration of presence has a cost, too.