Mike Griffiths asserts that when everyone on a team is recognised and treated as a volunteer their productivity far exceeds that of team members working for reward. He uses the diagram below to illustrate the scale of an individual's contribution to the team. (I've included Mike's descriptions):
Undermining/Resistance: People negatively impact the project, either intentionally or through misguided objectives and actions, their presence on the team actually has a net drain on project productivity.
Passive Compliance: People do generally work on to-do items, but without much thought and without any passion for the task or goal. (This is all too common in large organizations where for team members feel like cogs in a machine they have very little say in.)
Active Participation and Committed Dedication: This is where the good work starts getting done. People are engaged personally instead of merely by job obligation and are truly thinking about how best to solve problems and find new solutions. With brain engaged and a sense of ownership for task, the net contribution to the project are orders of magnitude higher than Passive Compliance contributors.
Passionate Innovation: This occurs when the task becomes the all consuming passion for those involved. Usually witnessed in start-ups and by partners in a business who's vision is being executed, passionate innovation can bring exceptional results and solutions.
Mike says that an individual's level of contribution is voluntary. Individuals choose where they want to operate on the scale. Extrinsic motivation probably causes them to turn up. A shared vision, belief in the goal/s and a sense of belonging to the team might cause them to contribute somewhere between active participation and committed dedication. But add intrinsic motivation to the mix and more individuals might work with passionate innovation.