Behind the Scenes of Duolingo.

With over 100 million users, Duolingo is the most popular education app in the world in Android and iOS. In the first part of this talk, we will describe the motivation for creating Duolingo, its philosophy, and some of the basic techniques used to successfully teach languages and keep users engaged. The second part will focus on the machine learning and natural language processing algorithms we use to model student learning. Proceedings of the 8th International Conference on Educational Data Mining 3 Proceedings of the 8th International Conference on Educational Data Mining 4 Personal Knowledge/Learning Graph George Siemens University of Texas Arlington and Athabasca University gsiemens@gmail.com Ryan Baker Teachers College Columbia University baker2@exchange. tc.columbia.edu Dragan Gasevic Schools of Education and Informatics University of Edinburgh dragan.gasevic@ed.ac.uk