What is the Optimum Team Size?

Back in the days when I studied group dynamics the research indicated that teams of 5-7 were “optimal” in the sense that teams of this size did better in lab experiments at solving problems than either smaller or larger groups. However I’ve recently seen business writing that states that optimum team size is 4-6 people. The authors didn’t mention the research behind this statement, but they are writers whom I respect and I am inclined to believe them. Being a data guy, though, I’d like to see the research. Does anyone know where this number (4-6) comes from?

In any event, both estimates include 5-6, so maybe that’s the size to shoot for.

UPDATE:

I found this article about this topic. While the numbers in the article are all over the place, the 5-6 number looks like it holds up pretty well. Of course, as everyone emphasizes, the number of members is just one of many criteria, and not the most important criteria. Still, if you team isn’t functioning well the team size is one place to look for the problem.