Next time you want your group to really shine, try bringing in an outsider, says a study in the journal Personality and Social Psychology Bulletin. Researchers at Northwestern University found that having a newcomer does more than introduce fresh ideas; it actually fosters more thinking and better results, especially when the newcomer agrees with some—but not all—existing group members. “Having people who don't think the same way is good,” says Northwestern psychologist Katherine W. Phillips, the study's lead author. “It is an uncomfortable situation, so you'll do a lot of hard work to understand the different perspectives.” The findings reflect our natural tendency to try to maintain harmony within groups, Phillips says.