Author ORCID Identifier

Date of Award

Fall 12-12-2022

Degree Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Sarah Brosnan

Second Advisor

Michael Beran

Third Advisor

Sarah Barber

Fourth Advisor

Erin Tone

Fifth Advisor

Marcela Benitez


For group-living species like humans and nonhuman primates, the ability to navigate social encounters and quickly process threats from others is a critical skill for maintaining group cohesion. Rapid detection of threatening stimuli, referred to as an attentional bias toward threat, is adaptive in that fast threat detection can lead to greater survival outcomes. Despite this fitness benefit, the evolutionary roots of attentional bias formation are not well understood. The present study used a comparative perspective to investigate attentional biases toward threat and the social factors associated with them in capuchin monkeys. I explored the hormonal mechanisms of attentional biases, specifically baseline fecal cortisol levels, indicative of stress levels, as well as the influence of oxytocin, a hormone implicated in social bond formation and affiliation. Attentional biases were determined using a dot-probe task that measured capuchins’ latency to respond to a target after viewing pairs of threatening and neutral conspecific faces or non-face stimuli. In study one, I examined (1) whether capuchins show attentional biases toward social or nonsocial stimuli and whether cortisol level predicted attentional bias formation. In study two, I investigated (2) the influence of manipulated oxytocin on attentional bias toward threat. In the final study, I examined (3) the relationship between social integration and attentional bias formation using social network analysis. Results suggest that as a group, capuchins do not show attentional biases toward threatening faces or non-face stimuli. Although cortisol and dominance were significant predictors of individual attentional bias, the effect size was small, making the relationship not likely to be biologically meaningful. Oxytocin did not influence attentional bias scores on unscrambled faces or objects. Lastly, individuals with high closeness centrality showed attentional biases toward unfamiliar threatening faces, indicating that socially connected individuals had rapid threat detection of out-group members compared to less-integrated individuals. Taken together, capuchins show individual differences in their propensity to exhibit attentional biases toward threat, but as a group they do not show robust evidence of attentional bias toward threatening faces or objects when assessed using a dot probe task.


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