Think global, act local: Preserving the global commons.

Oliver P. Hauser,Martin A. Nowak,Achim Hendriks,David G. Rand

doi:10.1038/srep36079

Abstract

Preserving global public goods, such as the planet’s ecosystem, depends on large-scale cooperation, which is difficult to achieve because the standard reciprocity mechanisms weaken in large groups. Here we demonstrate a method by which reciprocity can maintain cooperation in a large-scale public goods game (PGG). In a first experiment, participants in groups of on average 39 people play one round of a Prisoner’s Dilemma (PD) with their two nearest neighbours on a cyclic network after each PGG round. We observe that people engage in “local-to-global” reciprocity, leveraging local interactions to enforce global cooperation: Participants reduce PD cooperation with neighbours who contribute little in the PGG. In response, low PGG contributors increase their contributions if both neighbours defect in the PD. In a control condition, participants do not know their neighbours’ PGG contribution and thus cannot link play in the PD to the PGG. In the control we observe a sharp decline of cooperation in the PGG, while in the treatment condition global cooperation is maintained. In a second experiment, we demonstrate the scalability of this effect: in a 1,000-person PGG, participants in the treatment condition successfully sustain public contributions. Our findings suggest that this simple “local-to-global” intervention facilitates large-scale cooperation.

Highlights

Preserving global public goods, such as the planet’s ecosystem, depends on large-scale cooperation, which is difficult to achieve because the standard reciprocity mechanisms weaken in large groups
Previous experiments have found cooperation to be sustainable, in which group members interact in pairs with a large fraction of other members of the group, is untenable when groups are large. Does this reasoning imply that reciprocity cannot maintain cooperation in large groups? Here we show that the answer is “no.” We demonstrate that coupling a large repeated group cooperative dilemma to a sparse network of repeated pairwise reciprocal interactions averts the “tragedy of the commons,” and sustains cooperation in groups an order of magnitude larger than those studied previously
We observed significantly higher average contributions in the treatment compared to the control

Summary

Introduction

Preserving global public goods, such as the planet’s ecosystem, depends on large-scale cooperation, which is difficult to achieve because the standard reciprocity mechanisms weaken in large groups. We observe that people engage in “local-to-global” reciprocity, leveraging local interactions to enforce global cooperation: Participants reduce PD cooperation with neighbours who contribute little in the PGG. Everyone in the group is individually better off not contributing, and the “tragedy of the commons” ensues[2,3] To address this collective failure of cooperation, mechanisms have been proposed to promote cooperation in pairwise games or small groups[3,4,5]. The problem can be addressed by adding the opportunity for group members to punish or reward each other based on their contributions[11,26] Such pairwise interactions allow people to target their reciprocity and can stabilise cooperation in small groups.

Methods

Results

Conclusion