Divergent effects of oxytocin on eye contact in bonobos and chimpanzees

• Brooks, James

  Wildlife Research Center, Kyoto University･Kumamoto Sanctuary, Kyoto University

• Kano, Fumihiro

  Wildlife Research Center, Kyoto University･Kumamoto Sanctuary, Kyoto University

• Sato, Yutaro

  Wildlife Research Center, Kyoto University･Kumamoto Sanctuary, Kyoto University

• Yeow, Hanling

  Wildlife Research Center, Kyoto University･Kumamoto Sanctuary, Kyoto University

• Morimura, Naruki

  Wildlife Research Center, Kyoto University･Kumamoto Sanctuary, Kyoto University

• Nagasawa, Miho

  School of Veterinary Medicine, Azabu University

• Kikusui, Takefumi

  School of Veterinary Medicine, Azabu University

• Yamamoto, Shinya

  Wildlife Research Center, Kyoto University･Institute for Advanced Study, Kyoto University

Abstract

Oxytocin has drawn significant research attention for its role in modulating mammalian social behavior. Despite generally conserved roles, oxytocin can function differently even in closely related species. Previous studies have shown that bonobos and chimpanzees, humans’ two closest relatives, demonstrate considerable behavioral differences, including that bonobos look more at others’ eyes than chimpanzees. Oxytocin is known to increase attention to another’s eyes in many mammalian species (e.g. dogs, monkeys, and humans), yet this effect has not been tested in any nonhuman great ape species. This study examined how intranasally-administered oxytocin affects eye contact in bonobos and chimpanzees using eye tracking. Following administration of either oxytocin or saline control with a nebulizer, chimpanzees (n = 6) and bonobos (n = 5) were shown images of conspecific faces while their eye movement was recorded. Oxytocin changed the eye-looking behavior of bonobos and chimpanzees differently. We found that oxytocin increased eye contact in bonobos but not chimpanzees; while one chimpanzee showed an increase, interestingly, 5 out of 6 chimpanzees showed decreased looking to the eyes compared to the mouth, suggesting moderate eye avoidance. Given the importance of eye contact in their social interactions, our results suggest that oxytocin may play modulatory roles in bonobos’ and chimpanzees’ species-specific social behavior and underscore the importance of oxytocin in hominid social evolution.

Journal

• Psychoneuroendocrinology

  Psychoneuroendocrinology 125 105119-, 2021-03

  Elsevier BV

Keywords

• Oxytocin
• Eye contact
• Bonobos
• Chimpanzees
• Species differences
• Social attention

Details

• CRID: 1050569160001171200
• NII Article ID: 120006951772
• ISSN: 03064530
• DOI: 10.1016/j.psyneuen.2020.105119
• HANDLE: 2433/260851
• Web Site: https://api.elsevier.com/content/article/PII:S0306453020305424?httpAccept=text/xml
• Web Site: https://api.elsevier.com/content/article/PII:S0306453020305424?httpAccept=text/plain
• Text Lang: en
• Article Type: journal article
• Data Source:
  • IRDB
  • Crossref
  • CiNii Articles
  • KAKEN