Author ORCID Identifier

Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Sarah F Brosnan

Second Advisor

Sarah J Barber

Third Advisor

Michael J Beran

Fourth Advisor

Kevin M Swartout


Humans are an exceptionally prosocial species, but prosocial behavior is seen across the animal kingdom. Despite widespread observation of such behaviors, however, phylogenies of prosocial behavior have been difficult to establish, and little is known surrounding the proximate mechanisms in animals. This is in part because comparative experimental studies of prosocial behavior have had inconsistent results. There are likely many factors contributing to the variations in prosocial behavior, but the context within which a decision is made may be of particular importance, including experimental design, the social context, and the behavior of the partner. Recent research efforts have also begun to identify effects of immediately prior experiences on prosocial behavior. This dissertation specifically explores the effects of varying the nature of experiences (cooperative, competitive, or non-social tasks) and the outcomes of those experiences (whether a food reward was obtained or not) on subsequent prosocial choices in capuchin monkeys. Monkeys in this study did not overall choose to prosocially provision a partner more when their partner was present than when they were absent, despite demonstrating comprehension of the apparatus contingencies in a knowledge control following testing. Prosocial behavior also did not differ based on the nature or outcome of the prior experience. A measure of displacement behaviors (as a proxy of negative affect) was, however, related to how often subjects selected the prosocial option. Subjects showed increased negative affect after losing a competition compared to winning it, and an interaction with dominance such that any type of competitive experience was more negative than non-social experiences for monkeys who are subordinate to their partner. Finally, partner behavior during the prosocial task did not directly influence prosociality, but there were significant interactions between partner behavior and prior experiences in predicting prosocial choices. While capuchin monkeys did not overall behave prosocially in this study, one possibility is that they received too much training prior to testing that obscured interpretation of the task as a prosocial choice. This may indicate that prosocial behavior is context specific and/or a relatively weak effect. Future research into the interaction of affect and prosocial behavior may prove fruitful.


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