Hating the out-group

...psychologist Margo Monteith at the University of Kentucky in Lexington found that people can have prejudices against groups they know nothing about. She administered a test in which volunteers, under time pressure, had to associate a series of words with either "America" or a fictitious country she called "Marisat."

Volunteers more easily associated Marisat with such words as "poison," "death" and "evil," while associating America with "sunrise," "paradise" and "loyal."

"A large part of our self-esteem derives from our group membership," Monteith said. "To the extent we can feel better about our group relative to other groups, we can feel good about ourselves. It's likely a built-in mechanism."