The Limits of Moral Wiggle Room: Plausible Deniability in Public Good Games

Although in the lab we often assume a deterministic relationship between contributions to public goods and their returns, in real life this relationship is often uncertain: consider corruption or inefficiencies in governments, or areas where our knowledge is limited such as climate change mitigation. Rational individuals may change their contributions to respond to this uncertainty, but we may also observe a reduction in contributions if people take advantage of the plausible deniability about one’s actions that this uncertainty creates. The reduction of prosocial behaviour in the presence of plausible deniability was documented in Dana et al. (2007) and has since been widely replicated in two-person non-strategic settings. We test whether people exploit uncertainty in public good games (PGG) by using it as an excuse to free-ride. In two online studies that entail 5 between-subjects treatments, we varied whether the marginal per capita returns (MPCR) were certain or uncertain, and whether this uncertainty could give participants plausible deniability for their low or zero contributions. We found no change in free riding or average contributions across treatments, suggesting that cooperation under uncertainty is accurately captured by the standard PGGs with certain MPCR, and that uncertainty need not hamper cooperation in social dilemmas.