who gave the concept of ingroup and outgroup
Ingroups and outgroups The terminology was made popular by Henri Tajfel and colleagues during his work in formulating social identity theory. The significance of ingroup and outgroup categorization was identified using a method called the minimal group paradigm. Tajfel and colleagues found that people can form self-preferencing ingroups within a matter of minutes and that such groups can form even on the basis of seemingly trivial characteristics, such as preferences for certain paintings.[1][2][3][4][5]
Collective action Researchers Martijn van Zomeren, Tom Postmes, and Russell Spears conducted a meta-analysis of over 180 studies of collective action, in an attempt to integrate three dominant socio-psychological perspectives explaining antecedent conditions to this phenomenon â€“ injustice, efficacy, and identity.[2] In their resultant 2008 review article, an integrative Social Identity Model of Collective Action (SIMCA) was proposed which accounts for interrelationships among the three predictors as well as their predictive capacities for collective action.[2] An important assumption of this approach is that people tend to respond to subjective states of disadvantage, which may or may not flow from objective physical and social reality.