...Tasks such as document relevance assessment or image clustering can be represented in game form to achieve comparable label quality at significantly lower cost and high user satisfaction.
Citing:
If you use GeAnn, please refer to C. Eickhoff, C. G. Harris, A. P. de Vries and P. Srinivasan. "Quality through Flow and Immersion: Gamifying Crowdsourced Relevance Assessments". In SIGIR 2012