This dissertation aimed to detect and distinguish between minimal conditions for the interindividual-intergroup discontinuity effect. To date, research has focused onmoderators (e.g., Wildschut et al., 2003) and explanations (e.g, Wildschut & Insko, 2007) for the robust phenomenon that intergroup interactions are less cooperative than interindividual interactions. Here, “groups” were mainly treated as aggregates of positively interdependent actors, indicating an interdependence-based perspective of group formation. In bringing together research on interindividual-intergroup discontinuity and social identity theory (Tajfel & Turner, 1979, 1986) it has been reasoned that the effect is also in line with an identity-based perspective of group formation. Furthermore, it has been argued that interdependence-based and identitybased processes were typically confounded in previous research on interindividualintergroup discontinuity. The aim of the present thesis was to disentangle the effects of interdependencebased and identity-based group formation on the emergence of the discontinuity effect. It was hypothesized that mere identity-based group formation may be sufficient to decrease actors’ cooperation in mixed-motive situations, and therefore, to account for interindividual-intergroup discontinuity. Moreover, it was hypothesized that part of the classical discontinuity effect may be attributed to identity-based group processes.