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Heterogeneous networks do not promote cooperation when humans play a Prisoner's Dilemma.
Proc Natl Acad Sci U S A. 2012 Aug 07; 109(32):12922-6.PN

Abstract

It is not fully understood why we cooperate with strangers on a daily basis. In an increasingly global world, where interaction networks and relationships between individuals are becoming more complex, different hypotheses have been put forward to explain the foundations of human cooperation on a large scale and to account for the true motivations that are behind this phenomenon. In this context, population structure has been suggested to foster cooperation in social dilemmas, but theoretical studies of this mechanism have yielded contradictory results so far; additionally, the issue lacks a proper experimental test in large systems. We have performed the largest experiments to date with humans playing a spatial Prisoner's Dilemma on a lattice and a scale-free network (1,229 subjects). We observed that the level of cooperation reached in both networks is the same, comparable with the level of cooperation of smaller networks or unstructured populations. We have also found that subjects respond to the cooperation that they observe in a reciprocal manner, being more likely to cooperate if, in the previous round, many of their neighbors and themselves did so, which implies that humans do not consider neighbors' payoffs when making their decisions in this dilemma but only their actions. Our results, which are in agreement with recent theoretical predictions based on this behavioral rule, suggest that population structure has little relevance as a cooperation promoter or inhibitor among humans.

Authors+Show Affiliations

Instituto de Biocomputación y Física de Sistemas Complejos, Universidad de Zaragoza, 50018 Zaragoza, Spain.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

22773811

Citation

Gracia-Lázaro, Carlos, et al. "Heterogeneous Networks Do Not Promote Cooperation when Humans Play a Prisoner's Dilemma." Proceedings of the National Academy of Sciences of the United States of America, vol. 109, no. 32, 2012, pp. 12922-6.
Gracia-Lázaro C, Ferrer A, Ruiz G, et al. Heterogeneous networks do not promote cooperation when humans play a Prisoner's Dilemma. Proc Natl Acad Sci U S A. 2012;109(32):12922-6.
Gracia-Lázaro, C., Ferrer, A., Ruiz, G., Tarancón, A., Cuesta, J. A., Sánchez, A., & Moreno, Y. (2012). Heterogeneous networks do not promote cooperation when humans play a Prisoner's Dilemma. Proceedings of the National Academy of Sciences of the United States of America, 109(32), 12922-6. https://doi.org/10.1073/pnas.1206681109
Gracia-Lázaro C, et al. Heterogeneous Networks Do Not Promote Cooperation when Humans Play a Prisoner's Dilemma. Proc Natl Acad Sci U S A. 2012 Aug 7;109(32):12922-6. PubMed PMID: 22773811.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Heterogeneous networks do not promote cooperation when humans play a Prisoner's Dilemma. AU - Gracia-Lázaro,Carlos, AU - Ferrer,Alfredo, AU - Ruiz,Gonzalo, AU - Tarancón,Alfonso, AU - Cuesta,José A, AU - Sánchez,Angel, AU - Moreno,Yamir, Y1 - 2012/07/06/ PY - 2012/7/10/entrez PY - 2012/7/10/pubmed PY - 2012/10/16/medline SP - 12922 EP - 6 JF - Proceedings of the National Academy of Sciences of the United States of America JO - Proc Natl Acad Sci U S A VL - 109 IS - 32 N2 - It is not fully understood why we cooperate with strangers on a daily basis. In an increasingly global world, where interaction networks and relationships between individuals are becoming more complex, different hypotheses have been put forward to explain the foundations of human cooperation on a large scale and to account for the true motivations that are behind this phenomenon. In this context, population structure has been suggested to foster cooperation in social dilemmas, but theoretical studies of this mechanism have yielded contradictory results so far; additionally, the issue lacks a proper experimental test in large systems. We have performed the largest experiments to date with humans playing a spatial Prisoner's Dilemma on a lattice and a scale-free network (1,229 subjects). We observed that the level of cooperation reached in both networks is the same, comparable with the level of cooperation of smaller networks or unstructured populations. We have also found that subjects respond to the cooperation that they observe in a reciprocal manner, being more likely to cooperate if, in the previous round, many of their neighbors and themselves did so, which implies that humans do not consider neighbors' payoffs when making their decisions in this dilemma but only their actions. Our results, which are in agreement with recent theoretical predictions based on this behavioral rule, suggest that population structure has little relevance as a cooperation promoter or inhibitor among humans. SN - 1091-6490 UR - https://www.unboundmedicine.com/medline/citation/22773811/abstract/Heterogeneous_networks_do_not_promote_cooperation_when_humans_play_a_Prisoner's_Dilemma_ L2 - http://www.pnas.org/cgi/pmidlookup?view=long&pmid=22773811 DB - PRIME DP - Unbound Medicine ER -