The Anterior Insula Tracks Behavioral Entropy during an Interpersonal Competitive Game

Abstract

In competitive situations, individuals need to adjust their behavioral strategy dynamically in response to their opponent's behavior. In the present study, we investigated the neural basis of how individuals adjust their strategy during a simple, competitive game of matching pennies. We used entropy as a behavioral index of randomness in decision-making, because maximizing randomness is thought to be an optimal strategy in the game, according to game theory. While undergoing functional magnetic resonance imaging (fMRI), subjects played matching pennies with either a human or computer opponent in each block, although in reality they played the game with the same computer algorithm under both conditions. The winning rate of each block was also manipulated. Both the opponent (human or computer), and the winning rate, independently affected subjects' block-wise entropy during the game. The fMRI results revealed that activity in the bilateral anterior insula was positively correlated with subjects' (not opponent's) behavioral entropy during the game, which indicates that during an interpersonal competitive game, the anterior insula tracked how uncertain subjects' behavior was, rather than how uncertain subjects felt their opponent's behavior was. Our results suggest that intuitive or automatic processes based on somatic markers may be a key to optimally adjusting behavioral strategies in competitive situations.

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© 2015 Takahashi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Received: May 7, 2014; Accepted: March 2, 2015; Published: June 3, 2015. This study was supported by a Grant-in-Aid for Scientific Research on Innovative Areas "Founding a creative society via collaboration between humans and robots (No. 4101)" (24118708), Grant-in-Aid for Scientific Research on Innovative Areas "The study on the neural dynamics for understanding communication in terms of complex hetero systems (No. 4103)" (21120010 and 24120717), Grant-in-Aid for Young Scientists (B) No. 23700321, and Tamagawa University Global Center of Excellence grant from the Ministry of Education, Culture, Sports, Science and Technology, Japan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors thank Ralph Adolphs for his helpful comments on our manuscript, and Tomoki Haji for technical support. Author Contributions: Conceived and designed the experiments: HT KI TO. Performed the experiments: HT KI. Analyzed the data: HT KI MM. Contributed reagents/materials/analysis tools: HT KI MM. Wrote the paper: HT KI MM KM TO. Data Availability: All relevant data are within the paper and its Supporting Information files. Competing interests: The authors have declared that no competing interests exist.

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