Kai Otsubo
Kai Otsubo

Kai Otsubo

I am a Japanese social psychologist interested in collective phenomena that emerge from social interactions among many individuals. My current research focuses on intergroup conflict, large-scale cooperation among strangers, and their evolution in human history.

Recent Activity

  • I uploaded a preprint on the hump-shaped strategy in social dilemmas to arXiv.

Affiliation

  • Graduate School of Humanities and Sociology, The University of Tokyo (Lab website)
  • Japan Society for the Promotion of Science

Career

  • 2025/04 - Research Fellow DC2, Japan Society for the Promotion of Science

Education

  • 2024/04 - Graduate School of Humanities and Sociology, The University of Tokyo
  • 2022/04 - 2024/03 Graduate School of Human-Environment Studies, Kyushu University
  • 2018/04 - 2022/03 School of Education, Kyushu University

Selected Publications

Preprint

  1. Otsubo, K.*, Kido, Y.*, & Mori, R. (2026). Partial exploiters sustain cooperation: the hump-shaped strategy stably coexists with unconditional cooperators. arXiv:2604.23293. link

    *co-first authors

Peer-reviewed articles

  1. Otsubo, K. & Yamaguchi, H. (in press). Intergroup aggressors: When and why do they acquire a positive reputation in the in-group? Social Psychological Bulletin.

  2. Kuge, H.*, Otsubo, K.*, Hattori, K., Urakawa, M., & Yamada, Y. (2025). Attraction depending on the level of abstraction of the character descriptions. Collabra: Psychology, 11(1). link

    *co-first authors

  3. Otsubo, K., Nawata, K., & Yamaguchi, H. (2024). Conformity-based out-group aggression: Does an in-group audience intensify out-group aggression as a result of conformity? Japanese Psychological Research. link

  4. Otsubo, K., Masuda, Y., & Yamaguchi, H. (2023). "Watching eyes" do not strengthen the behavioral intention of donating blood: A high-powered pre-registered replication study. Letters on Evolutionary Behavioral Science, 14(1), 26-31. link

  5. Otsubo, K., & Yamaguchi, H. (2023). No significant effect of mortality salience on unconscious ethnic bias among the Japanese. BMC Research Notes, 16:91. link

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