Collaborative hierarchy maintains cooperation in asymmetric games

Alberto Antonioni,Marco Tomassini,Angel Sánchez,Katherine A Cronin,María Pereda

doi:10.1038/s41598-018-23681-z

Abstract

The interplay of social structure and cooperative behavior is under much scrutiny lately as behavior in social contexts becomes increasingly relevant for everyday life. Earlier experimental work showed that the existence of a social hierarchy, earned through competition, was detrimental for the evolution of cooperative behaviors. Here, we study the case in which individuals are ranked in a hierarchical structure based on their performance in a collective effort by having them play a Public Goods Game. In the first treatment, participants are ranked according to group earnings while, in the second treatment, their rankings are based on individual earnings. Subsequently, participants play asymmetric Prisoner’s Dilemma games where higher-ranked players gain more than lower ones. Our experiments show that there are no detrimental effects of the hierarchy formed based on group performance, yet when ranking is assigned individually we observe a decrease in cooperation. Our results show that different levels of cooperation arise from the fact that subjects are interpreting rankings as a reputation which carries information about which subjects were cooperators in the previous phase. Our results demonstrate that noting the manner in which a hierarchy is established is essential for understanding its effects on cooperation.

Highlights

While cooperation is common in many species[1,2,3], humans show this trait to a dramatically larger extent
We begin the presentation of our results by addressing the level of cooperation during Phase I in the Selfish (or Competitive) Hierarchy (SH) and Collaborative Hierarchy (CH) treatments; this phase was not included in the Random Hierarchy (RH) treatments
We must take into account that in SH treatments homo economicus individuals only benefit from maximizing their individual earnings, i.e. contributing no points to the group common pool, while in CH treatments their individual utility function corresponds to the maximization of their group payoff, i.e. contributing all the points of their round endowment

Summary

Introduction

While cooperation is common in many species[1,2,3], humans show this trait to a dramatically larger extent. Once not all individuals have the same strategic options and/or the consequences of their actions differ, those in a superior position can reap more benefits from cooperative actions at the expense of their partners, which in turn may lead the latter to stop cooperating It has been shown recently[18] that this is the case in experiments with humans designed to setups employed with primates[19,20]: Lower ranked subjects contribute less to a common goal when they benefit less than their partners. We contribute to the knowledge of cooperation on hierarchical structure by considering the case in which one’s ranking arises through competition with all others as in[18], or through some amount of cooperation We study these issues by means of a novel experimental design, which, as we will see below, allow us to shed light on hitherto unexplored facets of cooperative behavior. We employ a setting for testing the impact of hierarchy formation in short, but not one-shot, interactions, avoiding the direct reciprocity mechanism present for longer time encounters

Methods

Results

Conclusion