Eventually, all the important work is done before and after meetings by four or five influential members. As Parkinson would have it, and numerous studies now confirm, many hands do not make light work when it comes to teams. After devoting nearly 50 years to studying team performance, the late Harvard researcher J. Richard Hackman concluded that four to six members is the best team size for most tasks, that no work team should have more than 10 members, and that performance problems and interpersonal friction increase “exponentially as team size increases.”

These troubles arise because larger teams often place overwhelming “cognitive load” on individual members. As a group grows, each member devotes more time to coordination chores (and less time to actually doing the work), more hand-offs between the growing cast of members are required (creating opportunities for miscommunication and mistakes), and because each member must divide his or her attention among a longer list of colleagues, the team’s social glue weakens (and destructive conflict soars).

Melissa Valentine’s and Amy Edmondson’s study of a large hospital’s emergency department demonstrates the virtues of smaller teams. The crowd of 30 or so doctors and nurses who staffed the department at any given time were divided into multiple six-person “pods,” each led by a senior doctor or attending physician. After the change, information about patients flowed more quickly and accurately and personal relationships improved. Smaller teams reduced confusion and discomfort about who to ask for help and updates.

One nurse said: “Now there is much more of a sense of ownership of each other. I’ll say, ‘My pod isn’t running well. Where is my doctor?’ And he’ll be accountable to me. And the doctors will say, ‘Where are my nurses, who do I have today?’” People rarely, if ever, claimed each other in this way before the pods were implemented even if they were working together on many shared cases. A resident would have used more detached language like, “Who is this patient’s nurse?” – ignoring the relationship they themselves had with the nurse – rather than, “Where are my nurses?”

The pods also created big efficiency gains. Valentine and Edmondson analyzed data on 160,000 patients served by the department during the six months before the pods were created and the year after. After the pods, patient throughput time plummeted by about 40%, from about eight hours (8.34) to five hours (5.29) per patient, without increased staffing levels. This drop reflects not only a more efficient use of staff. Think of the patient's experience; five hours at the hospital sucks a lot less than eight.

The upshot is that many hands do not always make for light work, especially when it comes to team size. But some organizations encourage bloated teams with misguided incentives, rewarding managers more for growing their teams. When team members report that they are locked in dysfunctional conflict, suffering from indifference, making bad decisions, or missing deadlines, the first question we ask is “how big is the team?” If the answer is more than five or six members, especially more than than ten, some savvy subtraction or division can create striking improvements. As Valentine and Edmondson's research shows: Leaders become more effective. Efficiency improves. Interpersonal friction wanes. And strangers become friends.

Robert Sutton and Huggy Rao co-authored Scaling Up Excellence: Getting to More without Settling for Less. This piece is an edited excerpt from that book. They are also the co-directors of the new Designing Organizational Change Project at Stanford University. Robert Sutton is a professor at the Stanford University School of Engineering in Management Science and Engineering. Huggy Rao is a professor at the Stanford Graduate School of Business.