“At the core of most successful organizations are people who work well together,” Adrienne Sanders writes in Stanford Business.

“Happy collaborators are typically more productive and are less apt to look elsewhere for employment. But what are the circumstances that lead people to want to team up over and over again?”

New research by Stanford’s Daniel McFarland suggests that the reasons people continue to collaborate with others in their professional networks are quite different from the motives that led them to begin those relationships in the first place.

“Relationships, including professional partnerships, often begin because two (or more) individuals who work in the same place, see one another often, and have a lot in common. It’s easy to relate to someone the same age who shares your background and values. Beyond that, some people choose to associate with others in hopes of boosting their status or paycheck. ”

“But they often stay in these relationships due to ‘tie inertia,’ which is essentially a tendency to stay with what is known out of a sense of familiarity and commitment. This sense of obligation is strengthened if the people have invested a great deal of time and other resources in the partnership. It stays strong when partners have multiple types of association — they co-advise students and co-publish research, for example — because they know each other more deeply, and also because they have more resources to share."

He adds: "To form and sustain these ties, pairs of colleagues must interact frequently to share knowledge."

In short, McFarland says that people initiate relationships due to “opportunity and preference selection” but stay in them out of a sense of “obligation and complementary experience.”