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]
Outliers (book) While writing the book, Gladwell noted that "the biggest misconception about success is that we do it solely on our smarts, ambition, hustle and hard work."[4] In Outliers, he hopes to show that there are a lot more variables involved in an individual's success than society cares to admit,[4] and he wants people to "move away from the notion that everything that happens to a person is up to that person".[2] Gladwell noted that, although there was little that could be done with regard to a person's fate, society can still impact the "man"-affected part of an individual's success.[2] When asked what message he wanted people to take away after reading Outliers, Gladwell responded, "What we do as a community, as a society, for each other, matters as much as what we do for ourselves. It sounds a little trite, but there's a powerful amount of truth in that, I think."[2]