Genetic Evidence for Multiple Biological Mechanisms Underlying In-Group Favoritism

G. J. Lewis, T. C. Bates

Research output: Contribution to journalArticlepeer-review


In-group favoritism is ubiquitous and associated with intergroup conflict, yet is little understood from a biological perspective. A fundamental question regarding the structure of favoritism is whether it is inflexibly directed toward distinct, “essentialist” categories, such as ethnicity and race, or is deployed in a context-sensitive manner. In this article, we report the first study (to our knowledge) of the genetic and environmental structure of in-group favoritism in the religious, ethnic, and racial domains. We contrasted a model of favoritism based on a single domain-general central affiliation mechanism (CAM) with a model in which each domain was influenced by specific mechanisms. In a series of multivariate analyses, utilizing a large, representative sample of twins, models containing only the CAM or essentialist domains fit the data poorly. The best-fitting model revealed that a biological mechanism facilitates affiliation with arbitrary groups and exists alongside essentialist systems that evolved to process salient cues, such as shared beliefs and ancestry.
Original languageEnglish
Pages (from-to)1623-1628
JournalPsychological Science
Issue number11
Publication statusPublished - 1 Nov 2010


  • in-group favoritism
  • ethnocentrism
  • religion
  • genetics
  • twins


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