Dynamic, yet stable: separating within- and between-person components of collective action in support of a disadvantaged outgroup and its antecedents

Despite an increasing interest in the drivers of intergroup solidarity, the within-person longitudinal relationships between advantaged group members’ engagement for disadvantaged groups and its postulated antecedents remain scarcely tested. In the context of the refugee crisis following Russia’s invasion of Ukraine, we conducted a three-wave longitudinal survey (N_T1 = 804, N_T2 = 702, and N_T3 = 624) assessing Poles’ (the advantaged group) willingness to act for Ukrainians (the disadvantaged group), together with three hypothesized predictors—moral convictions, intergroup contact, and politicized identity. Employing a random intercept cross-lagged panel model that separates between- from within-person variance, we found that within-person changes in moral convictions and friendship contact directly predicted subsequent action intentions. Contrary to past theorizing, politicized identity emerged as consequence rather than an antecedent of collective action. Superficial intergroup contact indirectly predicted engagement intentions by facilitating cross-group friendship. We discuss the implications of our findings for current models of collective action.