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Bonobos (Pan paniscus) vocally protest against violations of social expectations

Clay, Zanna; Ravaux, Lucie; de Waal, Frans B.M.; Zuberbühler, Klaus

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Lucie Ravaux

Frans B.M. de Waal

Klaus Zuberbühler


Research has shown that great apes possess certain expectations about social regularities and both perceive and act according to social rules within their group. During natural and experimentally induced contexts, such as the inequitable distribution of resources, individuals also show protesting behaviors when their expectations about a social situation are violated. Despite broad interest in this topic, systematic research examining the nature of these expectations and the communicative signals individuals use to express them remains scant. Here, we addressed this by exploring whether bonobos (Pan paniscus) respond to violations of social expectations in naturally occurring social interactions, focusing on the vocal behavior of victims following socially expected and unexpected aggression. Expected aggression included conflicts over a contested resource and conflicts that were provoked by the victim. Unexpected aggression was any spontaneous, unprovoked hostility toward the victim. For each conflict, we also determined its severity and the composition of the nearby audience. We found that the acoustic and temporal structure of victim screams was individually distinct and varied significantly depending on whether or not aggression could be socially predicted. Certain acoustic parameters also varied as a function of conflict severity, but unlike social expectation, conflict severity did not discriminate scream acoustic structure overall. We found no effect of audience composition. We concluded that, beyond the physical nature of a conflict, bonobos possess certain social expectations about how they should be treated and will publicly protest with acoustically distinctive vocal signals if these expectations are violated.


Clay, Z., Ravaux, L., de Waal, F. B., & Zuberbühler, K. (2016). Bonobos (Pan paniscus) vocally protest against violations of social expectations. Journal of Comparative Psychology, 130(1), 44-54.

Journal Article Type Article
Acceptance Date Sep 28, 2015
Online Publication Date Feb 1, 2016
Publication Date Feb 1, 2016
Deposit Date Apr 19, 2017
Publicly Available Date Jun 24, 2019
Journal Journal of Comparative Psychology
Print ISSN 0735-7036
Electronic ISSN 0735-7036
Publisher American Psychological Association
Peer Reviewed Peer Reviewed
Volume 130
Issue 1
Pages 44-54
Related Public URLs


Accepted Journal Article (838 Kb)

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© 2016 APA, all rights reserved. This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.

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