Honesty mediates the relationship between serotonin and reaction to unfairness

Hidehiko Takahashi, Harumasa Takano, Colin F. Camerer, Takashi Ideno, Shigetaka Okubo, Hiroshi Matsui, Yuki Tamari, Kazuhisa Takemura, Ryosuke Arakawa, Fumitoshi Kodaka, Makiko Yamada, Yoko Eguchi, Toshiya Murai, Yoshiro Okubo, Motoichiro Kato, Hiroshi Ito, Tetsuya Suhara

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


How does one deal with unfair behaviors? This subject has long been investigated by various disciplines including philosophy, psychology, economics, and biology. However, our reactions to unfairness differ from one individual to another. Experimental economics studies using the ultimatum game (UG), in which players must decide whether to accept or reject fair or unfair offers, have also shown that there are substantial individual differences in reaction to unfairness. However, little is known about psychological as well as neurobiological mechanisms of this observation. We combined a molecular imaging technique, an economics game, and a personality inventory to elucidate the neurobiological mechanism of heterogeneous reactions to unfairness. Contrary to the common belief that aggressive personalities (impulsivity or hostility) are related to the high rejection rate of unfair offers in UG, we found that individuals with apparently peaceful personalities (straightforwardness and trust) rejected more often and were engaged in personally costly forms of retaliation. Furthermore, individuals with a low level of serotonin transporters in the dorsal raphe nucleus (DRN) are honest and trustful, and thus cannot tolerate unfairness, being candid in expressing their frustrations. In other words, higher central serotonin transmission might allow us to behave adroitly and opportunistically, being good at playing games while pursuing self-interest. We provide unique neurobiological evidence to account for individual differences of reaction to unfairness.

Original languageEnglish
Pages (from-to)4281-4284
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number11
Publication statusPublished - 2012 Mar 13
Externally publishedYes


  • Decision-making
  • Fairness
  • Positron emission tomography

ASJC Scopus subject areas

  • General


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