Zero-sum conditions can turn in-group attachment into out-group hostility.

Evidence

Previous researchers such as Brewer (2001) have theorized that ingroup and out-group attitudes become negatively correlated under zero-sum conditions. When the welfare of the in-group can only be achieved at the expense of the out-group, in-group positivity can lead to out-group hostility. — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 1109

Categorization

• corroborated: 2 independent passages support this claim — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 1109