A Service of Leibniz-Informationszentrum econstor Wirtschaft Leibniz Information Centre Make Your Publications Visible. zbw for Economics Zegners, Dainis; Sunde, Uwe; Strittmatter, Anthony Working Paper On the Causes and Consequences of Deviations from Rational Behavior CESifo Working Paper, No. 8341 Provided in Cooperation with: Ifo Institute – Leibniz Institute for Economic Research at the University of Munich Suggested Citation: Zegners, Dainis; Sunde, Uwe; Strittmatter, Anthony (2020) : On the Causes and Consequences of Deviations from Rational Behavior, CESifo Working Paper, No. 8341, Center for Economic Studies and Ifo Institute (CESifo), Munich This Version is available at: http://hdl.handle.net/10419/219159 Standard-Nutzungsbedingungen: Terms of use: Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Documents in EconStor may be saved and copied for your Zwecken und zum Privatgebrauch gespeichert und kopiert werden. personal and scholarly purposes. 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Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, If the documents have been made available under an Open gelten abweichend von diesen Nutzungsbedingungen die in der dort Content Licence (especially Creative Commons Licences), you genannten Lizenz gewährten Nutzungsrechte. may exercise further usage rights as specified in the indicated licence. www.econstor.eu 8341 2020 June 2020 On the Causes and Consequences of Deviations from Rational Behavior Dainis Zegners, Uwe Sunde, Anthony Strittmatter Impressum: CESifo Working Papers ISSN 2364-1428 (electronic version) Publisher and distributor: Munich Society for the Promotion of Economic Research - CESifo GmbH The international platform of Ludwigs-Maximilians University’s Center for Economic Studies and the ifo Institute Poschingerstr. 5, 81679 Munich, Germany Telephone +49 (0)89 2180-2740, Telefax +49 (0)89 2180-17845, email [email protected] Editor: Clemens Fuest https://www.cesifo.org/en/wp An electronic version of the paper may be downloaded · from the SSRN website: www.SSRN.com · from the RePEc website: www.RePEc.org · from the CESifo website: https://www.cesifo.org/en/wp CESifo Working Paper No. 8341 On the Causes and Consequences of Deviations from Rational Behavior Abstract This paper presents novel evidence for the prevalence of deviations from rational behavior in human decision making – and for the corresponding causes and consequences. The analysis is based on move-by-move data from chess tournaments and an identification strategy that compares behavior of professional chess players to a rational behavioral benchmark that is constructed using modern chess engines. The evidence documents the existence of several distinct dimensions in which human players deviate from a rational benchmark. In particular, the results show deviations related to loss aversion, time pressure, fatigue, and cognitive limitations. The results also demonstrate that deviations do not necessarily lead to worse performance. Consistent with an important influence of intuition and experience, faster decisions are associated with more frequent deviations from the rational benchmark, yet they are also associated with better performance. JEL-Codes: D010, D900, C700, C800. Keywords: rational strategies, artificial intelligence, behavioural bias. Dainis Zegner Uwe Sunde Rotterdam School of Management LMU Munich Erasmus University / The Netherlands Munich / Germany [email protected] [email protected] Anthony Strittmatter University of St. Gallen / Switzerland anthony [email protected] May 26, 2020 The authors thank K. Anders Ericsson, Armin Falk, Daniel Goller, Matthias Lang, David Smerdon, Andreas Steinmayr, and audiences at the CRC TRR 190 Meeting in Tutzing for useful comments. Uwe Sunde gratefully acknowledges financial support of the Deutsche Forschungsgemeinschaft (CRC TRR 190 Rationality and Competition). Anthony Strittmatter gratefully acknowledges the hospitality of CESifo. “I don’t believe in psychology. I believe in good moves.” (Bobby Fischer) 1 Introduction Traditionally, economists have focused on a rational decision maker – the “homo eco- nomicus” – to model human behavior. The observation of various deviations of behavior from the benchmark of optimizing rational decision making has motivated an entire field, behavioral economics. Research in this field has identified a plethora of different, partly distinct and partly interacting, behavioral biases, which are related to cognitive lim- itations, stress, limited memory, preference anomalies, and social interactions, among others. These biases are typically established by comparing actual behavior against a theoretical benchmark, often in simplistic, unrealistic, or abstract settings that are unfa- miliar to the decision makers. Field evidence for behavioral biases among professionals is still scarce, mostly because of the difficulty to establish a rational benchmark in complex real-world settings. Consequently, most contributions focus on documenting a behav- ioral deviation in one particular dimension. This makes it often difficult to compare the behavioral biases documented in the literature. Moreover, deviations from rational behavior are usually seen as being related to suboptimal performance. However, this connotation often rests on a priori reasoning or value judgments because it is typically even harder or impossible to identify the consequences of deviations from the rational benchmark than the deviations themselves. This paper breaks new ground in the documentation of behavioral deviations from the rational benchmark, as well as of their causes and consequences, by investigating the behavior of professional chess players. Conceptually, chess is ideally suited to address the research question about the typology and emergence of behavioral deviations from the rational benchmark. First, chess provides a clean and transparent decision environment that allows observing individual choices in a sequential game of perfect information. Second, chess players are typically seen as the prototypes of rational, forward-looking strategic behavior. This is even more the case for professional chess players participating 1 in tournaments with high stakes and incentives to win a game. Third, chess provides a unique source of information about behavior at extremely high resolution and accuracy. Fourth, the availability of chess engines makes it possible to construct a clean rational benchmark for behavior. We develop a new methodology for identifying deviations from rational behavior as well as their implications for performance that makes use of artificial intelligence tech- niques embodied in modern chess engines. This methodology is based on the fact that chess engines provide a detailed quantitative and objective evaluation of a given config- uration of pieces on the board in terms of the associated winning odds for each player, and of the complexity of a decision in terms of a precise measure of the difficulty of identifying the optimal move in a given configuration. Importantly, the logic of chess engines is based on the notion of mutually best responses, thus applying rational de- cision making. Using this, we compare the actual moves of human decision makers to the best conceivable move in the respective configuration. This best conceivable move is determined by a “super chess engine” whose performance exceeds that of the best humans by far. To construct a rational benchmark, we also replicate each configuration observed in a large data set of chess games and determine the decision of a “restricted chess engine” that still plays mutual best response, but that is comparable in terms of playing strength to human players and simulates play against another chess engine of similar strength. Like the human decisions, these replicated decisions of the restricted chess engine are then evaluated in comparison to the moves suggested by the super chess engine. This makes it possible to identify deviations of human behavior from the ratio- nal benchmark, as well as the consequences of these deviations for performance using within-person variation at the level of individual moves. The comparison of the relative performance of humans to that of a comparably strong chess engine identifies deviations from fully rational behavior by decision makers that are experts in the respective decision environment. This methodology allows us to investigate the exact circumstances and factors that lead individual players to deviate from rational behavior. In particular, the detailed information about the evaluation of 2 a given configuration, the time left for decision making, complexity, and the time used for a given move provides a unique possibility to decompose different candidates for behavioral biases within the same person and game. Moreover, the difference between the relative performance of humans in comparison to the super chess engine and the relative performance of the restricted engine in comparison to the super chess engine shed light on the consequences of the behavioral deviations on performance. This allows us to investigate not only whether humans