Linguistic Harbingers of Betrayal: A Case Study on an Online Strategy Game

Proceedings of the 53rd Annual Meeting of the Association for Computational Linguistics and the 7th International Joint Conference on Natural Language Processing, pages 1650–1659, Beijing, China, July 26-31, 2015. c⃝2015 Association for Computational Linguistics Linguistic Harbingers of Betrayal: A Case Study on an Online Strategy Game Vlad Niculae,1 Srijan Kumar,2 Jordan Boyd-Graber,3 Cristian Danescu-Niculescu-Mizil1 1Cornell University, 2University of Maryland, 3University of Colorado vlad@cs.cornell.edu, srijan@cs.umd.edu, Jordan.Boyd.Graber@colorado.edu, cristian@cs.cornell.edu Abstract Interpersonal relations are fickle, with close friendships often dissolving into en- mity. In this work, we explore linguis- tic cues that presage such transitions by studying dyadic interactions in an on- line strategy game where players form al- liances and break those alliances through betrayal. We characterize friendships that are unlikely to last and examine temporal patterns that foretell betrayal. We reveal that subtle signs of imminent betrayal are encoded in the conversational patterns of the dyad, even if the victim is not aware of the relationship’s fate. In particular, we find that lasting friend- ships exhibit a form of balance that man- ifests itself through language. In contrast, sudden changes in the balance of certain conversational attributes—such as positive sentiment, politeness, or focus on future planning—signal impending betrayal. 1 Introduction A major focus in computational social science has been the study of interpersonal relations through data. However, social interactions are compli- cated, and we rarely have access all of the data that define the relationship between friends or enemies. As an alternative, thought experiments like the prisoner’s dilemma (Axelrod and Dion, 1988) are used to explain behavior. Two prisoners—denied communication—must decide whether to cooper- ate with each other or defect. Such simple and elegant tools initially helped understand many real world scenarios from pricing products (Rosenthal, 1981) to athletes doping (Buechel et al., 2013). Despite its power, the prisoner’s dilemma remains woefully unrealistic. Cooperation and betrayal do not happen in a cell cut off from the rest of the world. Instead, real interactions are mediated by communication: promises are made, then broken, and met with recriminations. To study the complex social phenomenon of be- trayal, we turn to data and observe the players of Diplomacy (Sharp, 1978), a war-themed strategy game where friendships and betrayals are orches- trated primarily through language. Diplomacy, like the prisoner’s dilemma, is a repeated game where players choose to either cooperate or betray other players. Diplomacy is so engaging that it is played around the world, not only casually as a board game but also over the Internet and in formal settings such as world championships.1 Players converse throughout the game and victory hinges on enlisting others’ support through persuasive- ness and cunning duplicity. To illustrate the social relations that carry out throughout the game, con- sider the following exchange between two Diplo- macy allies: Germany: Can I suggest you move your armies east and then I will support you? Then next year you move [there] and dismantle Turkey. I will deal with England and France, you take out Italy. Austria: Sounds like a perfect plan! Happy …

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