  Badges are commonly used in online platforms as incentives for promoting
contributions. It is widely accepted that badges "steer" people's behavior
toward increasing their rate of contributions before obtaining the badge. This
paper provides a new probabilistic model of user behavior in the presence of
badges. By applying the model to data from thousands of users on the Q&A site
Stack Overflow, we find that steering is not as widely applicable as was
previously understood. Rather, the majority of users remain apathetic toward
badges, while still providing a substantial number of contributions to the
site. An interesting statistical phenomenon, termed "Phantom Steering,"
accounts for the interaction data of these users and this may have contributed
to some previous conclusions about steering. Our results suggest that a small
population, approximately 20%, of users respond to the badge incentives.
Moreover, we conduct a qualitative survey of the users on Stack Overflow which
provides further evidence that the insights from the model reflect the true
behavior of the community. We argue that while badges might contribute toward a
suite of effective rewards in an online system, research into other aspects of
reward systems such as Stack Overflow reputation points should become a focus
of the community.
