{"title":"Capuchin monkeys' responses to inequity in a group context","authors":"Mayte Martínez , Sarah F. Brosnan","doi":"10.1016/j.anbehav.2025.123257","DOIUrl":null,"url":null,"abstract":"<div><div>Noticing how ones' outcomes compare to your partner’s can help you decide who to cooperate with, promoting cooperative relations that are beneficial for both. As such, understanding how animals respond to unequal outcomes is key to uncovering evolutionary roots of cooperation and fairness. Recent research has demonstrated that various animal species respond negatively when they receive less preferred rewards than a partner for completing the same task, often refusing the reward or withdrawing from the task. While most studies on inequity aversion focus on dyadic contexts, which ensure experimental control, these settings do not capture the complexity of natural social environments and may limit partner choice. In this study, we explored responses of brown capuchin monkeys, <em>Sapajus</em> [<em>Cebus</em>] <em>apella</em>, to inequity in a more naturalistic group context, extending their well-documented inequity aversion from dyadic contexts. We compared both food refusals and the number of trades in a token exchange task across various conditions (advantageous and disadvantageous inequity, contrast and equity) involving different combinations of food values. Considering refusals, as in dyadic studies, brown capuchin monkeys were sensitive to disadvantageous inequity, refusing low-value rewards when their partners received higher-value rewards, but rarely rejecting medium- or high-value food. Unexpectedly, we found a negative response to contrast and advantageous inequity, neither of which had been observed in previous studies. In contrast, the number of exchanges capuchins initiated was driven by food value, with no effect of what their partner received. We discuss various factors, such as group dynamics and constraints of the tasks that may explain differential responses in group versus dyadic contexts pointing to new research directions. This study highlights the importance of more naturalistic conditions to achieve a nuanced understanding of the impact of the social context on primate decision making.</div></div>","PeriodicalId":50788,"journal":{"name":"Animal Behaviour","volume":"226 ","pages":"Article 123257"},"PeriodicalIF":2.3000,"publicationDate":"2025-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Animal Behaviour","FirstCategoryId":"99","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0003347225001848","RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"BEHAVIORAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Noticing how ones' outcomes compare to your partner’s can help you decide who to cooperate with, promoting cooperative relations that are beneficial for both. As such, understanding how animals respond to unequal outcomes is key to uncovering evolutionary roots of cooperation and fairness. Recent research has demonstrated that various animal species respond negatively when they receive less preferred rewards than a partner for completing the same task, often refusing the reward or withdrawing from the task. While most studies on inequity aversion focus on dyadic contexts, which ensure experimental control, these settings do not capture the complexity of natural social environments and may limit partner choice. In this study, we explored responses of brown capuchin monkeys, Sapajus [Cebus] apella, to inequity in a more naturalistic group context, extending their well-documented inequity aversion from dyadic contexts. We compared both food refusals and the number of trades in a token exchange task across various conditions (advantageous and disadvantageous inequity, contrast and equity) involving different combinations of food values. Considering refusals, as in dyadic studies, brown capuchin monkeys were sensitive to disadvantageous inequity, refusing low-value rewards when their partners received higher-value rewards, but rarely rejecting medium- or high-value food. Unexpectedly, we found a negative response to contrast and advantageous inequity, neither of which had been observed in previous studies. In contrast, the number of exchanges capuchins initiated was driven by food value, with no effect of what their partner received. We discuss various factors, such as group dynamics and constraints of the tasks that may explain differential responses in group versus dyadic contexts pointing to new research directions. This study highlights the importance of more naturalistic conditions to achieve a nuanced understanding of the impact of the social context on primate decision making.
期刊介绍:
Growing interest in behavioural biology and the international reputation of Animal Behaviour prompted an expansion to monthly publication in 1989. Animal Behaviour continues to be the journal of choice for biologists, ethologists, psychologists, physiologists, and veterinarians with an interest in the subject.