who has coined the concept of in group and out group
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]
Primary and secondary groups People in a secondary group interact on a less personal level than in a primary group. Since secondary groups are established to perform functions, peopleâ€™s roles are more interchangeable. A secondary group is one you have chosen to be a part of. They are based where many people can meet close friends or people they would just call acquaintances. Secondary groups are groups in which one exchanges explicit commodities, such as labour for wages, services for payments, etc. Examples of these would be employment, vendor-to-client relationships, etc.