In public good games, voluntary contributions tend to start of high and decline as the game is repeated. If high contributors are matched, however, contributions tend to stay high. We propose a formalization predicting that high contributors will selfselect into groups committed to charitable...

Are some individuals generally more pro-social than others? If so, socially beneficial commitments could serve as a costly screening device helping the pro-social to match. We present a public good game experiment in which subjects choose between two group types: in blue groups, subjects receive...