How to hire voluntary helpers? We shed new light on this question by reporting a field experiment in which we invited 2,859 students to help at the 'ESA Europe 2012' conference. Invitation emails varied non-monetary and monetary incentives to convince subjects to offer help. Students could apply...

This paper investigates the effect of different communication channels on promise-making and promise-keeping in a helping situation. Four treatments differ with respect to the communication channel employed to solicit unincentivized cooperation, i.e., face-to-face, phone call and two different...

This paper investigates the effect of different communication channels on promise-making and promise-keeping in a helping situation. Four treatments differ with respect to the communication channel employed to solicit unincentivized cooperation, i.e., face-to-face, phone call and two different...

This paper investigates the effect of different communication channels on promise-making and promise-keeping in a helping situation. Four treatments differ with respect to the communication channel employed to solicit unincentivized cooperation, i.e., face-to-face, phone call and two different...

This paper investigates the effect of different communication channels on promise-making and promise-keeping in a helping situation. Four treatments differ with respect to the communication channel employed to solicit unincentivized cooperation, i.e., face-to-face, phone call and two different...