Small groups perform best when they operate collaboratively, and not merely as drones subordinated to a leader. The team leader’s job is to establish the conditions that enable team members to collaborate competently; the leader needs to spell out exactly where teams should end up, but not dictate the step-by-step process of getting there. Leaders who act boldly and intelligently can make significant differences in teams’ effectiveness—but no matter how the leaders act, teams become less effective as they grow in size. Ideal team size, Hackman says, is about six people; performance problems increase exponentially as team size increases beyond that, and the impact of leadership becomes quickly diffused.
via theatlantic.com