A good way to start a negotiation is the common enemies negotiating strategy. What is the common enemies negotiating strategy? It’s something I first learned of when I interviewed Stuart Diamond about his win-win negotiation philosophy. To establish rapport with someone, or curry their favor, talk to them about a common enemy – lawyers or the New York Yankees, for example. Establishing a common enemy builds trust quickly. Try it next time you’re on an airplane or waiting in line outside a bar. It works. You probably already do it and just didn’t have a name for it.

A Personality and Social Psychology Bulletin study, which was brought to my attention by New York Magazine, confirms the value of establishing common enemies.

Lead researcher Jennifer Bosson and grad student Jonathan Weaver had undergrads complete a study for class credit. The students filled out forms that indicated the name of a professor they liked or disliked. A mediator gave them another student’s form and casually mentioned that the other student liked or disliked the same faculty member. The students with negative impressions of the same professor felt they shared a bond.

As Diamond noted in his interview with me, the other person in this scenario need not be a stranger. The other person can be your boss or a salesman or your girlfriend.

Bosson told me that, while she is not a negotiation expert, if Diamond is correct, then it does seem like finding a common enemy could facilitate effective negotiation.

“Our work suggests that people feel increased familiarity, liking and closeness to those with whom they discover a shared negative attitude of a third party — what you call a ‘common enemy,'” she says. “And if one of the keys to successful negotiation is establishing liking and trust with one’s negotiation partner, then it certainly seems like finding a common enemy could be an effective way to promote such liking.”

Bosson urges people to take caution before employing the strategy for gain. In the study, researchers knew beforehand who people disliked and, seemingly inadvertently, mentioned to them that another person shared the same negative attitude. In real-life situations you do not always know beforehand that your dislike will be shared.

“In expressing a dislike, one risks discovering that one’s conversation partner does not agree, and this can lead to reduced closeness and liking, which is the opposite of the desired outcome,” Bosson says. “Therefore, in negotiation situations, it’s perhaps best to try first to ascertain one’s partner’s dislikes before forging ahead with potentially unpopular opinions. One would not, for example, want to start badmouthing Sarah Palin only to discover that one’s negotiation partner is a huge Palin fan.”

In their recent article, Bosson and Weaver found evidence that common enemies makes a stranger feel more familiar. She says it’s socially appropriate to express positive attitudes toward others, whereas it’s less acceptable to express dislikes of other people. Therefore, expressed dislikes reveal more about the underlying character of the speaker. Any behaviors that violate social norms are interpreted as revealing more about the actor.

“In general, shared attitudes — both positive and negative — lead to increased liking for strangers, but we propose that shared negative attitudes provide an extra bit of perceived familiarity,” Bosson says. “You feel like you know just a little bit more about who this person is underneath when you learn that you both dislike the same third party. This heightened familiarity is enough to make people feel a little more liking and closeness toward the stranger; after all, we like what’s familiar.

Try the common enemies negotiating strategy next time you negotiate. Just make sure your boss is not a litigious Yankees fan first.

(Joe Donatelli is Senior Editor of Made Man. He recently wrote about Stuart Diamond’s Negotiating Strategy. E-mail him at jdonatelli[at]breakmedia.com.)