Replicating and extending evidence for the unilaterality of group loyalty

Intergroup competition was a powerful selection force shaping human coalitional psychology. Individuals presenting multiple loyalties among competing groups represent a threat for defection. Thus, there is likely to be a social norm that loyalty should be unilateral among competing groups. Four studies provided evidence supporting this notion, however some of the results have been challenged and suggested to be products of methodological confounds. Also, some participants reported being confused by some of the experimental content, thus providing inaccurate responses. The current study is a modified replication of the survey project (Study 3), controlling for the suggested methodological confounds and revising instructions to clarify participant tasks. The original effects were reproduced, increasing the confidence in the interpretation of results. In addition, data were gathered in an additional set of items that were original to this study. These items directly tested the relative mutual exclusivity of loyalties based on the relationships among teams. Results from these items provide further evidence for a social norm of unilateral group loyalty.