Nudges and Monetary Incentives: A Green Partnership?

Shifting individual behaviour is an important tool for addressing environmental issues and there is a wide literature evaluating interventions to encourage pro-environmental behaviour. One important but under-researched area is the effect of combining interventions to affect behaviour. In this paper, we evaluate the effects of two interventions – monetary incentives and nudges – on nature restoration volunteering. We use a two-by-two treatment design to evaluate the individual and combined effects of the interventions in a field experiment setting. We find that the monetary incentive significantly increases volunteering behaviour, despite concerns incentives may crowd out motivation, but that nudging alone is ineffective at shifting behaviour. However, there are considerable positive synergies between the monetary incentive and nudge. The monetary incentive becomes more than twice as effective when it is combined with a nudge. We find support for our theoretical prediction that this synergy arises because the nudge reduces motivational crowding out effects from the incentive. Our results have important policy implications, showing that concerns around motivation crowding out from monetary incentives could be mitigated by simple, low-cost nudges.