Social identity as the basis of group entitativity: Elaborating the case for the "science of social groups per se"

In his seminal 1958 paper Campbell focused on the question of whether social aggregates such as groups can be considered to be real and have the same status as physical entities. He argued that the domain of psychology is considered more “real” than that of sociology because in the former the biological boundary of the person defines the psychological entity. Where groups are involved there is no clear-cut diagnosed entity. In defense of the position that groups are real, Campbell highlighted four general principles that define when discrete elements are perceived as part of a whole (common fate, similarity, proximity, and pregnance). He then applied these to physical objects (such as rats, stones, teacups) and to social groups. Campbell concluded that the social group can be considered an entity, and this perception therefore opens up the possibility of there being a “separate level of analysis from the biological and psychological” (p. 24) and a “science of social groups per se” (p. 24).