Since Mancur Olson's “Logic of collective action” it is common conviction in social sciences that in large groups the prospects of a successful organization of collective actions are rather bad. Following Olson's logic, the impact of an individual's costly contribution becomes smaller if the...

The dynamics of behavior observed in standard public-good experiments can be explained by imperfect conditional cooperation combined with social learning (Fischbacher and Gächter, 2010). But it is unclear what determines first-round contributions. We argue that first-round contributions depend...