The Role of Non-Binding Pledges in Social Dilemmas with Mitigation and Adaptation

This study presents experimental results on the role that non-binding pledges have on the ability of groups to manage a threat of probabilistic group damages in two separate environments. We focus on an environment where in addition to collective mitigation, agents can work autonomously to protect themselves from the damages if they occur (adaptation). The tension is that mitigation and adaptation investments are strategic substitutes. We test the hypothesis that non-binding pledges are more effective in a world with both mitigation and adaptation strategies, compared to mitigation only. First-period results show that (i) consistent with previous literature, pledges in a mitigation-only environment do not increase average investments in collective mitigation, but (ii) when both mitigation and adaptation opportunities exist, pledges lead to higher investment in collective mitigation, lower investment in adaptation and increased efficiency. Although the average treatment effect disappears over time as the amount pledged decreases, pledges remain significant predictors of mitigation investments over the course of the experiment.