When Nobody Wins Kyle Gorman and Charles Yang In memoriam Morris Halle. Abstract We argue that lexical gaps arise when language learners fail to find productive rules in a morphological domain. Using the Tolerance Principle as a formal model of productivity, we show that lexical gaps can be predicted on purely numerical grounds using lexical statistics, with case studies on Spanish, Polish, and Russian. The learnability approach taken here leads to simpler theories of morphology. Keywords Productivity · Lexical gap · Tolerance principle · Language acquisition · Corpus statistics · Computational linguistics 1 Introduction As young children vividly illustrate with their performance on the wug-test (Berko 1958), the ability to generalize linguistic patterns to novel items is a core property of language. It thus comes as a surprise when we stumble into a dark and dusty corner This chapter adapts and expands upon analyses first presented in chapter 5 of Yang (2016). We thank Margaret Borowczyk for assistance with Polish, and Jennifer Preys and Vitaly Nikolaev for assistance with Russian. We are also grateful for the comments and suggestions provided by Wolfgang Dressler, Gregory Stump, and the editors of the present volume. K. Gorman () Department of Linguistics, Graduate Center of the City University of New York, New York, NY, USA Google, Inc., New York, NY, USA e-mail: kbg@google.com; kgorman@gc.cuny.edu C. Yang Department of Linguistics, University of Pennsylvania, Philadelphia, PA, USA e-mail: charles.yang@ling.upenn.edu © Springer Nature Switzerland AG 2019 F. Rainer et al. (eds.), Competition in Inflection and Word-Formation, Studies in Morphology 5, https://doi.org/10.1007/978-3-030-02550-2_7 169