Many systems involve the allocation of rewards for achievements, and these rewards produce a set of incentives that in turn guide behavior. Such effects are visible in many domains from everyday life, and they are increasingly forming a designed aspect of participatory on-line sites through the use of badges and other reward systems. 
We consider several aspects of the interaction between rewards and incentives in the context of collective effort, including a framework for reasoning about on-line user activity in the presence of milestones and badges, and some recent applications of this framework that we have pursued on sites including Stack Overflow and Coursera. We then consider the role of behavioral biases in reasoning about progress toward long-range goals, and to this end we propose a graph-theoretic framework for analyzing procrastination and other forms of planning behavior that are inconsistent over time. 
The talk includes joint work with Ashton Anderson, Dan Huttenlocher, Jure Leskovec, and Sigal Oren.

Video Recording