Is social identity belief independent?

In this paper we aim to disentangle the effects on in-group favoritism driven by beliefs from those stemming from group identity, with the final goal of testing the relative power of three potential explanations of this bias: The Beliefs Driven Explanation (BDE), the Group Identity Explanation (GIE) and the Belief-mediated Group Identity Explanation (BGE). The BDE suggests that in-group favoritism is only driven by the desire not to let others’ expectations down. The GIE claims that people have a preference, per se, for members of their group. According to the BGE, people also have a preference for members of their group, but this is mediated by their second-order beliefs. To this aim, we built an experimental design able to produce exogenous variations in both group membership and expectations, hence providing a genuine test for the rationale of in-group bias. The results of our experiment suggest that beliefs per se are not a significant explanation of in-group favoritism and hence do not provide support to the BDE. Our experimental evidence does not provide support also to the BGE. We conclude that our experiment suggests to single out the GIE as the most powerful explanation of social identity.