This book adopts a social-psychological perspective in studying natural groups, focusing on relationships between groups that have been living in the same environment for a long time. A theoretical model is proposed concentrating on norm violation as a triggering factor of attributions and reactions between two social groups. In an elaboration of this framework, called Norm Violation Theory, this process is conceptualized as being affected by a number of social-psychological context factors: identification with their own group, intergroup attitudes, perceived differences in power, and feelings of fraternal relative depravation. Each of these factors can influence the manifestation of negative intergroup behaviour and contribute to a possible escalation of conflict. The theory also proposes that norms of redress, existing between groups embedded within an overall cultural or organizational entity, become operative as soon as an escalating process is set in motion.