People play economic games. Researchers force them to do this in order to identify people’s propensities for different types of social behavior. They gather small groups of subjects and give them fictitious money, which can be invested in joint projects in the hope of making a real profit or saved, while receiving income from the investments of other group members. There are always significantly more cooperators in such games than individual players, and approximately half of the players, when making contributions, are guided by how much other participants invest, and only a quarter of the participants never give a penny for joint projects.