Résumé
Using a simple decision-theoretic approach, we formalize how agents with different kinds of intrinsic motivations react to the introduction of monetary incentives. We contend that empirical results supporting the existence of a crowding-out effect under various legal procedures hide a more complex reality, where some individuals contribute thanks to these additional monetary incentives while others reduce their contributions. Our approach allows us to study the theoretical ability of the self selection mechanism (Mellström and Johannesson in J Eur Econ Assoc 6:845–863, 2008; Beretti et al. in Kyklos 66(1):63–77, 2013) to reduce the likelihood to backfire against the cause it is meant to promote. This mechanism consists of a monetary payment for the pro-social behavior and it offers agents the choice to either keep the money for themselves or to direct it to a charity. We show that this legal procedure dominates others more classical procedures because it taps wisely into the motivational heterogeneity of individuals. It uses a self-selection mechanism to match adequate monetary incentives with individuals’ types regarding intrinsic motivations. It may even turn a situation subject to crowding-out into a crowding-in outcome.