Some social scientists say that in-group/out-group biases are hard-wired into the human brain. Even without overt prejudice, it is cognitively convenient for people to sort items into categories and respond based on what is usually associated with those categories: a form of statistical discrimination, playing the odds.

Organizational structures that allow divisions and departments to own their turf and people with long tenure to take root creates the same hardened group distinctions as Congressional redistricting to produce homogeneous voting blocs - all of which makes it easier to resist compromise, let alone collaboration.

Tribalism reflects strong ethnic or cultural identities that separate members of one group from another, making them loyal to people like them and suspicious of outsiders, which undermines efforts to forge common cause across groups.

Rosabeth Moss Kanter Quotes