After studying over 180 google teams they didn't find any evidence that the composition of the teams mattered (i.e. friends outside of work, male/female, introverts, extroverts, intelligence). Instead what they focused on were the “group norms” or unwritten rules of how the groups interacted with each other. There were two norms that were most important to a successful group.

1) Members spoke in roughly the same proportion, what the researchers call, ‘‘equality in distribution of conversational turn-taking.’’

2) Members all had “average social sensitivity”. They could understand how other team members felt based on non-verbal queues. The underperforming teams had low sensitivity amongst the team members.