Do Birds of a Feather Flock Together?: The Relationship between Similarity and Altruism in Social Networks

Hum Nat (2013) 24:336347

DOI 10.1007/s12110-013-9174-z

Do Birds of a Feather Flock Together?

The Relationship between Similarity and Altruism in Social Networks

Oliver Curry & Robin I. M. Dunbar

Published online: 24 July 2013# Springer Science+Business Media New York 2013

Abstract Cooperation requires that individuals are able to identify, and preferentially associate with, others who have compatible preferences and the shared background knowledge needed to solve interpersonal coordination problems. The present study investigates the nature of such similarity within social networks, asking: What do friends have in common? And what is the relationship between similarity and altruism? The results show that similarity declines with frequency of contact; similarity in general is a significant predictor of altruism and emotional closeness; and, specifically, sharing a sense of humor, hobbies and interests, moral beliefs, and being from the same area are the best predictors. These results shed light on the structure of relationships within networks and provide a possible checklist for predicting attitudes toward strangers, and in-group identification.

Keywords Cooperation . Altruism . Emotional closeness . Similarity. Homophily. Social networks

The simplest kind of cooperationmutualism, or collaborationoccurs in situations in which individuals are able to provide certain benefits to one another at no net cost to themselves. Collaboration requires that individuals are able to identify others not only with compatible preferences (for example, joint interest in a common project), but also with the shared background knowledge needed to solve interpersonal coordination problems. Coordination problems arise when individuals are uncertain about when, where or how to act in order to realise a mutual benefit. In game-theoretic terms, coordination problems occur when there are multiple, mutually beneficial equilibria, but where uncertainty exists about which equilibrium others will pick, and hence players face an equilibrium-selection problem. Humans face a vast array of such coordination problems in everyday life, the solutions to which often involve recourse to a body of

O. Curry (*)

Institute of Cognitive and Evolutionary Anthropology, University of Oxford,64 Banbury Road, Oxford OX2 6PN, UKe-mail: [email protected]

R. I. M. Dunbar

Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK

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shared expectations of behaviorvariously called norms, conventions, or social constructionswhich serve as guides to local equilibria. These shared expectations constitute...