Model: Motivational Factors for Complex Work
In is book Drive: The Surprising Truth About What Motivates Us, Daniel H. Pink identified three vital sources of extrinsic motivation for individuals engaged in something more complex than simple, straightforward tasks.
Many people have heard of these three factors via this lively video created by RSA Animate.
BTW, I would point out that these factors are strongly correlated with some of the Core Design Principles for the Efficacy of Groups, with Self-Determination Theory and with the the DRAMMA List of Psychological Needs.