Not just babble: Opening the black box of communication in a voluntary contribution experiment

We let subjects in a voluntary contribution experiment make non-binding numerical announcements about their “possible” contributions and, in some treatments, send written promises to contribute specific amounts. We find that announcements were responded to both by others’ announcements and by real play, for example announcements led to costly punishment when found to be misleading. We also find that adding pre-play announcements to treatments...