The likes that bind: Even novel opinion sharing can induce opinion-based identification.

Research has found that psychological groups based on opinion congruence are an important group type. Previous research constructed such groups around opinions potentially connected to pre-existing identities. We strip away the socio-structural context by using novel opinions to determine whether opinion congruence alone can be a category cue which can foster identification and whether such group identification mediates the relationship between opinion exposure and opinion polarization. We assess this across two pre-registered online interactive experiments. Study 1 (N = 1168) demonstrate that opinion congruence fostered stronger identity than minimal groups. Study 2 (N = 505) demonstrate that opinion congruence fostered stronger identification than non-opinion congruence. The relationship between opinion exposure and opinion polarization occurs through group identification in both. Results demonstrate that (novel) opinions can be self-categorization cues informing identification and influencing opinion polarization.