Proceedings of the 54th Annual Meeting of the Association for Computational Linguistics, pages 1848–1858, Berlin, Germany, August 7-12, 2016. c 2016 Association for Computational Linguistics A Trainable Spaced Repetition Model for Language Learning Burr Settles∗ Duolingo Pittsburgh, PA USA burr@duolingo.com Brendan Meeder† Uber Advanced Technologies Center Pittsburgh, PA USA bmeeder@cs.cmu.edu Abs