Approval Voting Behavior in Doodle Polls

Doodle is a simple and popular online system for scheduling events. It is an implementation of the approval voting mechanism, where candidates are the time slots and each responder approves a subset of the slots. We analyze all the Doodle polls created in the US from JulySeptember 2011 (over 340,000 polls), consisting of both hidden polls (where you cannot see other people’s votes) and open polls (where you can see all the previous responses). By analyzing the differences in behavior in hidden and open polls, we gain unique insights into strategies that people apply in natural voting settings. Responders in open polls are more likely to approve slots that are very popular or very unpopular, but not intermediate slots. We show that this behavior is inconsistent with models that have been proposed in the voting literature, and propose a new model based on combining personal and social utilities to explain the data.