Human behavior in Prisoner's Dilemma experiments suppresses network reciprocity

TL;DR

This study reveals that human behavior in Prisoner's Dilemma experiments results in consistent cooperation levels across different network structures, challenging previous beliefs about network influence.

Contribution

It demonstrates that real human behavior overrides network effects, showing cooperation levels are similar in structured and well-mixed populations.

Findings

Human behavior leads to uniform cooperation levels across networks.

Network structure does not significantly influence cooperation in human experiments.

Behavioral heterogeneity explains cooperation outcomes better than network topology.

Abstract

During the last few years, much research has been devoted to strategic interactions on complex networks. In this context, the Prisoner's Dilemma has become a paradigmatic model, and it has been established that imitative evolutionary dynamics lead to very different outcomes depending on the details of the network. We here report that when one takes into account the real behavior of people observed in the experiments, both at the mean-field level and on utterly different networks the observed level of cooperation is the same. We thus show that when human subjects interact in an heterogeneous mix including cooperators, defectors and moody conditional cooperators, the structure of the population does not promote or inhibit cooperation with respect to a well mixed population.