  The Web has enabled one of the most visible recent developments in
education---the deployment of massive open online courses. With their global
reach and often staggering enrollments, MOOCs have the potential to become a
major new mechanism for learning. Despite this early promise, however, MOOCs
are still relatively unexplored and poorly understood.
  In a MOOC, each student's complete interaction with the course materials
takes place on the Web, thus providing a record of learner activity of
unprecedented scale and resolution. In this work, we use such trace data to
develop a conceptual framework for understanding how users currently engage
with MOOCs. We develop a taxonomy of individual behavior, examine the different
behavioral patterns of high- and low-achieving students, and investigate how
forum participation relates to other parts of the course.
  We also report on a large-scale deployment of badges as incentives for
engagement in a MOOC, including randomized experiments in which the
presentation of badges was varied across sub-populations. We find that making
badges more salient produced increases in forum engagement.
