We are taught that the optimal team size for a Scrum team is 7 plus or minus 2. We hear about it in our Certified ScrumMaster Training and from others. It is something that I often took for granted. After all, that was the Scrum rule! My own experiences have backed it up seeing the dynamic of groups larger than 7+-2 changing quickly, especially evident in the Daily Scrum. But, other than my experiences, why? It isn’t just because Ken Schwaber and Jeff Sutherland said so ..
In 1956, George A. Miller of Harvard University published a paper in Psychological Review that talked about this. In his paper, The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information he talks about how the number of objects that an average human can hold in working memory is 7 plus or minus 2.
In a 2006 blog entry, Pete Abilla, in his article Team Dynamics: Size Matters Redux, he adds some additional insight into the complexity of communication as more people are added to the mix.