Cooperation and Contagion in Web-Based, Networked Public Goods Experiments

TL;DR

This study investigates how network topology influences cooperation in public goods games, finding that network structure has little effect and that cooperation is only contagious among direct neighbors, challenging existing theories.

Contribution

The paper provides empirical evidence from 113 web-based experiments showing that network topology does not significantly impact cooperation, and that cooperation contagion is limited to direct neighbors.

Findings

Network topology had no significant effect on cooperation levels.

Players respond to neighbors' contributions but do not always increase cooperation.

Cooperation contagion is limited to immediate neighbors.

Abstract

A longstanding idea in the literature on human cooperation is that cooperation should be reinforced when conditional cooperators are more likely to interact. In the context of social networks, this idea implies that cooperation should fare better in highly clustered networks such as cliques than in networks with low clustering such as random networks. To test this hypothesis, we conducted a series of web-based experiments, in which 24 individuals played a local public goods game arranged on one of five network topologies that varied between disconnected cliques and a random regular graph. In contrast with previous theoretical work, we found that network topology had no significant effect on average contributions. This result implies either that individuals are not conditional cooperators, or else that cooperation does not benefit from positive reinforcement between connected neighbors. We then tested both of these possibilities in two subsequent series of experiments in which artificial seed players were introduced, making either full or zero contributions. First, we found that although players did generally behave like conditional cooperators, they were as likely to decrease their contributions in response to low contributing neighbors as they were to increase their contributions in response to high contributing neighbors. Second, we found that positive effects of cooperation were contagious only to direct neighbors in the network. In total we report on 113 human subjects experiments, highlighting the speed, flexibility, and cost-effectiveness of web-based experiments over those conducted in physical labs.