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]
Encomienda The encomienda was strongly based on the encomendado's tribal identity. Mixed-race (Mestizo) individuals, for example, could not by law be subjected to the encomienda. This moved many Amerindians to deliberately seek to dilute their tribal identity and that of their descendants as a way for them to escape the service, by seeking intermarriage with people from different ethnicities, especially Spaniards or Creoles. In this way the encomienda somewhat weakened Amerindians' tribal identification and ethnicity, which in turn diminished the pool of available encomendados.