In the past, typically teams would be assigned to work on tasks for several weeks or months, the team’s members would be fully dedicated to one project at a time, and they would be physically located together. All of these made understanding the team boundaries a relatively simple and straightforward task. In those situations – where membership is clear – teams found it is easy to establish a shared understanding of their task and processes, and to form an “esprit de corps”. Such teams functioned efficiently and effectively because team members’ understandings were aligned.Today, this esprit de corps may start to falter even in cases where there exists a clearly articulated organisational chart showing the team’s make-up and where the project launch included clear communication about who’s working with whom. The issue is that the model of the team that governs your team member’s day to day interactions is not, in fact, that organisational chart hanging on the wall, but rather the model of the team that person holds between their ears. We base our actions on our mental representations – representations that are socially constructed, and can evolve over time. As a result, some weeks down the line you may discover that information is being shared with people you consider outside the team, or your team’s group-level cognition and collective intelligence is failing to capture critical information. These consequences and more can arise because we are unaware of the differing models of membership held in our teams.