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Do Birds of a Feather Flock Together?

The Relationship between Similarity and Altruism in Social Networks

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.

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Acknowledgments

This research is supported by the SOCIALNETS Project, funded by an EU-FP7 grant. RD’s research is also supported by the British Academy Centenary Research Project and by an ERC Advanced Grant. Thanks also to Susanne Shultz, and Thomas Pollett for statistical advice.

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Correspondence to Oliver Curry.

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Curry, O., Dunbar, R.I.M. Do Birds of a Feather Flock Together?. Hum Nat 24, 336–347 (2013). https://doi.org/10.1007/s12110-013-9174-z

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Keywords

  • Cooperation
  • Altruism
  • Emotional closeness
  • Similarity
  • Homophily
  • Social networks