Size Matters

A great deal of the work KI does to provoke innovation involves operating in groups and teams. We have nothing against individual genius; in fact we value and recognize that a single person’s vision can power an innovation effort. But in almost every field – and we work with many, from scientists, professors and teachers to aide organizations or NGO field workers – it is more often the deliberate mixing of minds and talents that results in a tangible, innovative outcome.

Except group work can be clunky and cumbersome. You have to spend longer clarifying the objectives, aligning resources and getting people on board. Sometimes, it can seem nearly impossible to achieve the consensus necessary to advance within a task. Groups are a powerful mechanism to produce innovative solutions, but getting to that product can be arduous, particularly if it’s not well facilitated.

How can group work be made more effective, and – dare we say – enjoyable? Clearly, there are many factors at play, but the number of people in a group can make a difference. Too big and it’s too hard to incorporate everyone’s best thinking and steer toward a decision. Too small and there might not be enough diversity of thinking. Add to that a noticeable trend of larger teams being assembled to address highly complex research questions, even though research shows that smaller teams will be more innovative.

At an Ideas Lab, we invite a good-sized group to explore an issue in depth and generate new research ideas. Depending on a number of factors – budget, funding, complexity of the issue, courage of the funder – there might be anywhere between 16 and 40 participants. But, we limit the activities we do as a full group. Our session design will include several activities for smaller round-table groups to define and discuss the scope of the challenge, usually in groups of 5-7 people. We never based this on any particular marker; it’s simply emerged organically as a sub-group size that seems to work.

Midway through the Sandpit process, when we stop engineering the group mixes, and let participants gravitate to the subjects and colleagues they choose, the same grouping magic seems to apply. The groups often self-calibrate to a number that hovers around 5 to 7 members. Sometimes smaller groups form and do fine, but rarely will larger ones succeed.

There are a number of different research studies, theories, formulas, and even a law about the optimal size for a well functioning group. The answer is pretty consistent: somewhere between 5 and 9 people. In software development, the term 7 plus/minus 2 comes up often. This might be borrowed from a communication theory about how many words or data points a person can retain, or it could just be a coincidence. But it holds true: we’ve found that if there are too many people around the table, the activity tends to be dominated by the louder personalities. It’s hard for everyone to get “air time” and some participants will choose to clam up rather than press themselves too fiercely into a discussion or a brainstorming. On the other hand, if you have too few people in the group, then there may not be enough diversity of perspectives to ignite a provocative discussion or generate novel ideas.

There’s further research that points toward a significant improvement in productivity if the number of members in a group is odd rather than even. This could be simply about having a tie-breaker, which is often helpful in decision making. With the exception of situations where people need to be able to split into working pairs – and even then a trio can usually work – there seems to be a case for keeping your total head count small, and at an odd integer.

We cannot omit the two-pizza rule. According to’s Jeff Bezos, if your team can eat more than two pizzas at a meeting, it might be too large.

There’s probably no hard and fast rule on group size, and certainly the nature of the task informs the numbers and the skill-set required in a team. And for generating new ideas, it’s not only size that matters, assembling the right people from different disciplines or departments is another thing to consider. It’s the alchemy of diverse members of the group that spurs new thinking. Still, if within a project you can keep the members of your working teams to a handful, chances are the group will work easier, faster, and with more novel results. And everyone can have a second slice.


Know further: How bigger is not necessarily better for team science. Why small teams are better than large ones. And how large teams develop science, and small teams disrupt it. More on the two-pizza rule here and here. Then there’s the Dunbar rule. There’s an interesting and constructive debate about the perfect group of 8-12. (Do read the comments on this post to get the full discussion.) Listen to a Podcast about the optimal team size.