Skills of social interaction are the top predictor of team effectiveness:

The most important factor in group effectiveness turned out not to be what everybody thinks – cohesion, motivation, leadership. Instead, it’s the social sensitivity of the team members, their skills of social interaction. That’s what encourages those patterns of “idea flow,” to use Pentland’s term. Those three elements of interaction were about as important as all other factors—individual intelligence, technical skills, members’ personalities, and anything else you could think of—put together.