Randall Peterson, founding director of the Leadership Institute at London Business School, studies coworker dynamics. He says lately, the idea of head-to-head competition for advancement has gone out of style in favor of a more cooperative ideal. In reality, he says, interpersonal relationships at work can be both. Sometimes you cooperate closely with colleagues. Sometimes you compete directly with them. And sometimes it’s most effective to work independently. He explains how to deal with each scenario. And he shares how managers can help their teams find the right balance. Peterson is a coauthor of the HBR article “When to Cooperate with Colleagues and When to Compete.”