A Game-Theoretic Analysis of the ESP Game ∗ PRELIMINARY DRAFT : COMMENTS WELCOME

In recent years, there has been a great deal of progress in “Games with a Purpose,” interactive games that users play because they are fun, with the added benefit that they are doing useful work in the process. The ESP game, developed by von Ahn and Dabbish [24], is an example of such a game devised to label images on the web. Since labeling images is a hard problem for computer vision algorithms and can be tedious and time-consuming for humans, the ESP game provides humans with incentive to do useful work by being enjoyable to play. We present a simple game-theoretic model of the ESP game and characterize the equilibrium behavior in our model. Our equilibrium analysis supports the fact that users appear to be coordinating on low effort words. We provide an alternate model of utility and show that equilibrium behavior in this model achieves more desirable outcomes, from the system designer’s perspective. We also give sufficient conditions for coordinating on high effort words to be a BayesianNash equilibrium. Our results suggest the possibility of formal incentive design in achieving desirable system-wide outcomes in this area of “human computation” in complementing existing considerations of robustness against cheating and human factors.