Proctor, Darby

Assistant Professor, Psychology
Psychology, School of

Humans sometimes make economic decisions that go against their own self interests. Why, for example, do people gamble when everyone knows they are going to lose money? In my research, I look for the evolutionary origins of these decision-making biases. It may be that these patterns of behavior were useful in our evolutionary past. In order to explore these types of issues, I research decision-making in nonhuman primates. I am particularly interested in how decision-making processes are influenced by the social dynamics within groups.

Currently, I am researching a number of topics within behavioral economics with the animals housed at the Brevard Zoo. At the zoo, my work is conducted with spider monkeys and ring-tailed lemurs.

I teach courses in the animal behavior concentration for psychology undergraduates. 

Educational Background

B.A. University of Florida

M.S.M. University of Florida

Ph.D. Georgia State University

Additional Duties

Co-Chair, School of Psychology Diversity Committee

Current Research

Behavioral economics and decision-making in nonhuman primates.

Selected Publications

Peer-Reviewed Articles

Proctor, D., Williamson, R. A., Latzman, R. D., Brosnan, S. F., & de Waal, F. B. M. (2014). Gambling primates: reactions to a modified Iowa Gambling Task in humans, chimpanzees and capuchin monkeys. Animal Cognition, 17, 983-995. doi:10.1007/s10071-014-0730-7

Proctor, D., Williamson, R. A., de Waal, F. B. M., & Brosnan, S. F. (2013). Chimpanzees play the ultimatum game. Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1220806110

Proctor, D., & Brosnan, S. F. (2013). Visual processing speed in capuchin monkeys (Cebus apella) and rhesus macaques (Macaca mulatta). International Journal of Comparative Psychology, 26, 166-175.

Salwiczek, L. H., Prétôt, L., Demarta, L., Proctor, D., Essler, J., Pinto, A. I., . . . Bshary, R. (2012). Adult cleaner wrasse outperform capuchin monkeys, chimpanzees and orangutans in a complex foraging task derived from cleaner–client reef fish cooperation. PloS One, 7(11), e49068.

Proctor, D. P., Lambeth, S. P., Schapiro, S. J., & Brosnan, S. F. (2011). Male chimpanzees' grooming rates vary by female age, parity, and fertility status. American Journal of Primatology, 73(10), 989-996. doi:10.1002/ajp.20964

Horner, V., Proctor, D., Bonnie, K. E., Whiten, A., & de Waal, F. B. M. (2010). Prestige affects cultural learning in chimpanzees. PloS One, 5(5), e10625. Retrieved from

Campbell, M. W., Carter, J. D., Proctor, D., Eisenberg, M. L., & de Waal, F. B. M. (2009). Computer animations stimulate contagious yawning in chimpanzees. Proceedings of the Royal Society B: Biological Sciences, 276(1676), 4255-4259. doi:10.1098/rspb.2009.1087

Reviews, Commentaries and Chapters

Brosnan, S. F., de Waal, F. B. M., & Proctor, D. (2015). Reciprocity in non-human primates. In S. Preston (Ed.), The Interdisciplinary Science of Consumption. Oxford: Oxford University Press.

Proctor, D., Williamson, R. A., de Waal, F. B. M., & Brosnan, S. F. (2013). Reply to Henrich and Silk: Toward a unified explanation for apes and humans. Proceedings of the National Academy of Sciences, 110(33), E3050. doi:10.1073/pnas.1309100110

Proctor, D., Williamson, R. A., de Waal, F. B. M., & Brosnan, S. F. (2013). Reply to Jensen et al.: Equitable offers are not rationally maximizing. Proceedings of the National Academy of Sciences, 110(20), E1838. doi:10.1073/pnas.1304306110

Proctor, D., Brosnan, S. F., & de Waal, F. B. M. (2013). How fairly do chimpanzees play the ultimatum game? Communicative & Integrative Biology, 6(3), e23819. Retrieved from

Proctor, D. (2013). Animal Friendships by Anne Innis Dagg. The Quarterly Review of Biology, 88(3), 246-247. doi:10.1086/671517

Proctor, D., & Brosnan, S. F. (2011). Political primates: What other primates can tell us about the evolutionary roots of our own political behavior. In P. Hatemi & M. McDermott (Eds.), Man is by Nature a Political Animal: Evolution, Biology and Politics (pp. 47-71). Chicago: University of Chicago Press.