"As human beings, we tend to favor people we think are like us or have something in common with us—and we’re often wary of people who are different. 

"Evolution made us this way so that we could find allies against outside threats. The problem comes when this old instinct to prefer our “in-group” leads us to discriminate, dehumanize, or act violently toward others we perceive as “the other” or members of the “out-group.”

"Surprisingly, it doesn’t take much for us to create or expand in-groups. Studies have shown that even minimal similarities—like wearing the same-colored shirt—can prime us to prefer members of our in-group in relation to out-group members.

"What allows us to get past that tendency to be so easily biased for and against people? A new study suggests one step: focus on the need to cooperate."

Article: Just Thinking About Cooperation Can Make You Less Prejudiced