Sarah Brosnan

Ph.D., Emory University, 2004
Associate Professor
Member, Cognitive Sciences Program
Member, NBN Program
Associate Professor, Philosophy 
Associate Member, Neuroscience Institute
710 Urban Life, 404-413-6301
Language Research Center, 404-241-8164


My research interests lie in the intersection of complex social behavior and cognition. More specifically, I am interested in mechanisms underlying cooperation, reciprocity, inequity, and other economic decisions in nonhuman primates from an evolutionary perspective. This includes, but is not limited to, questions of what decisions individuals make and how they make these decisions, how their social or ecological environments affect their decisions and interactions, and under what circumstances they can alter their behaviors contingent upon these inputs.

One of my current projects is an NSF funded investigation comparing three species of nonhuman primates and humans in their response to a cooperative economic game.  Often, these studies are not comparable due to methodological differences, minimizing the effectiveness of the comparative approach and providing little insight into the evolution of the behaviors.  We are currently investigating whether these species will cooperate when given the opportunity to do so and how factors such as partner identity, equity in payoffs, and the context of the task affect their performance.  This research is being done jointly at the Language Research Center of GSU and with Bart Wilson at the Interdisciplinary Center for Economic Science of George Mason University.

A second major interest of mine is the evolution of responses to inequity.  This requires animals to take in to account both their own and others’ rewards or procedures, and makes subjective assessments of their outcome based upon these changing parameters, and likely involves emotional responses as well as conscious decision making.  In the past I have demonstrated this phenomenon in both capuchin monkeys and chimpanzees, as well as demonstrating that subjects take account of both the rewards and their partners’ behaviors and that social context affects reactions.  I have also investigated the flip side of inequity, or how individuals respond when they are advantaged, to more fully integrate this research with the human literature.  Currently we are working on assessing how group dynamics affect the response, how control of the situation alters responses, and the relative impact of inequity towards the self versus inequity towards another, as well as extending this research to other species. 

Finally, I am interested in barter, or exchange, behavior in nonhuman primates.  I have investigated how capuchin monkeys and chimpanzees understand the barter interaction, and ongoing work assesses their abilities to utilize a barter efffectively.  The exchange paradigm can also be effectively used to investigate other behaviors such as inequity and endowment effects.  I currently have several ongoing projects investigating barter and using the paradigm as a tool to investigate other pheneomena.

External Grants


NSF “Discovering solutions to games of conflict and trust” with co-PIs Bart Wilson and Michael Beran ($475,217, in total costs)


NICHD “The emergence of self-control: Comparative behavioral and neurobiological assessments” with PI Michael Beran and co-PI Rebecca Williamson (NIH P01HD060563)


NSF CAREER Award “Understanding responses to inequitable
outcomes” (SES 0847351)


 NSF Human Social Dynamics grant “Understanding of strategic
economic interactions through cross-species analysis” with co-PIs Bart Wilson & Michael Beran (SES 0729244)


Edited Volumes

Brosnan, SF & Bshary, R (2010). “Cooperation & Deception: From Evolution to Mechanisms” Issue 365 of the Philosophical Transactions of the Royal Society Series B

Selected Peer Reviewed Publications

Brosnan, SF, Parrish, A, Beran, MJ, Flemming, T, Heimbauer, L, Talbot, C, Lambeth, SP, Schapiro, SJ, Wilson, BJ (2011) Responses to the assurance game in monkeys, apes, and humans using equivalent procedures. PNAS, 10(8), 3442-3447. doi: 10.1073/pnas.1016269108.

Talbot, C, Williams, L, & Brosnan, SF (2011) Squirrel monkeys’ response to inequitable outcomes indicates a behavioral convergence within new world monkeys. Biology Letters. doi: 10.1098/rsbl.2011.0211.

Brosnan, SF (2011) Property in non-human primates. New Directions for Child & Adolescent Development. H. Ross & O. Friedman (Eds.) 132: 9-22.

Hopper, LM, Schapiro, SJ, Lambeth, SP & Brosnan, SF (2011) Conservation of socially learnt preferences by chimpanzees. Animal Behavior. DOI: 10.1016/j.anbehav.2011.03.002.

Brosnan, SF (2011) A hypothesis of the co-evolution of cooperation and inequity. Frontiers in Decision Neuroscience, 5:43, doi: 10.3398/fnins.2011.00043.

Brosnan, SF (2011) An evolutionary perspective on morality. Journal of Economic & Behavioral Organization 77, 23-30. doi:10.1016/j.jebo.2010.04.008

Brosnan, SF, Flemming, T., Talbot, C. F., Mayo, L., & Stoinski, T (2011) Responses to inequity in orangutans. Folia Primatologica, 82: 56-70. DOI: 10.1159/000328142.

Brosnan, SF, Bshary, R, Salwiczek, L (2010) What makes cooperation complex? Philosophical Transactions of the Royal Society Series B, 365, 2699-2710. doi: 10.1098/rstb.2010.0154

Brosnan, SF, Houser, D, Xiao, E, Leimgruber, K, Chen, T, & de Waal, FBM (2010) Competing demands of prosociality & equity in monkeys. Evolution & Human Behavior. doi:10.1016/j.evolhumbehav.2010.02.003

Brosnan, SF, Talbot, C, Ahlgren, M, Lambeth, SP, & Schapiro, SJ. (2010) Mechanisms underlying the response to inequity in chimpanzees, Pan troglodytes. Animal Behaviour. doi:10.1016/j.anbehav.2010.02.019

Brosnan, SF, Newton-Fisher, NE, & van Vugt, M (2009) A melding of the minds: When primatology meets social psychology. Personality & Social Psychology Review. doi:10.1177/1088868309335127

Brosnan, SF & Beran, MJ (2009) Bartering behavior between conspecifics in chimpanzees, Pan troglodytes. Journal of Comparative Psychology 123, 181-194.

Brosnan, SF, Jones, OD, Lambeth, SP, Mareno, MC, Richardson, AS, & Schapiro, SJ (2007) Endowment effects in chimpanzees. Current Biology 17 (19): 1-4.

Van Wolkenten, Megan, Brosnan, SF, & de Waal, FBM (2007) Inequity responses of monkeys modified by effort. PNAS 104: 18854-18859.

Brosnan, SF (2006) Nonhuman species’ reactions to inequity & their implications for fairness. Journal of Social Justice 19: 153-185.

Brosnan, SF, Freeman, C, & de Waal, FBM (2006) Equitable behavior, not reward distributions, affect capuchin monkey’s (Cebus apella) reactions in a cooperative task. American Journal of Primatology 68: 713-724.

Silk, JB, Brosnan, SF, Vonk, J, Henrich, J, Povinelli, D, Richardson, A, Lambeth, SP, Mascaro, J, & Schapiro, SJ. (2005) Chimpanzees are indifferent to the welfare of unrelated group members. Nature 437: 1357-1359.

Brosnan, SF, Schiff, HC, & de Waal, FBM (2005) Chimpanzees’ (Pan troglodytes) reactions to inequity during experimental exchange. Proceedings of the Royal Society of London, Series B 1560: 253-258.

Brosnan, SF & de Waal, FBM (2004) Socially learned preferences for differentially rewarded tokens in the brown capuchin monkeys (Cebus apella). Journal of Comparative Psychology 118 (2): 133-139.

Brosnan, SF & de Waal, FBM (2003) Monkeys reject unequal pay. Nature 425: 297-299.

Brosnan, SF & de Waal, FBM (2002). Proximate mechanisms of cooperation & reciprocity. Human Nature 13 (1): 129-152.

Selected Chapters

Brosnan , SF (in press) Evidence for Moral Behaviors in Non-human Primates (ed. Markus Christensen and Carel van Schaik) in Empirically Informed Ethics. Morality Between Facts and Norms. Springer.

Proctor, D & Brosnan, SF (in press) Political Primates: What Other Primates Can Tell Us about the Evolutionary Roots of Our Own Political Behavior (ed. R McDermott & P Hatemi) in Endogenous Political Preferences in Humans. University of Chicago Press.

Brosnan, SF (2010) What do capuchin monkeys tell us about cooperation? (eds. DR Forsyth & CL Hoyt) in For the Greater Good of All:Perspectives on Individualism, Society, & Leadership in the Jepson Series on Leadership Studies. Palgrave Macmillan Publishers.

Brosnan, SF (2010) Prosocial behavior in chimpanzees. (eds. E Lonsdorf, S Ross, & T Matsuzawa) in The Chimpanzee Mind. University of Chicago Press.

Brosnan, SF (2008). Responses to inequity in nonhuman primatesresponses in Neuroeconomics: Decision Making and the Brain (ed. P Glimcher, E Fehr, C Camerer, R Poldrack). Elsevier, pp. 285-302.

Brosnan, SF (2008) Fairness & other-regarding preferences in non-human primates In Moral Markets: The critical role of values in the economy (ed. PJ Zak). Princeton, NJ, Princeton University Press, pp 77-106. Preprint available on SSRN at

Brosnan, SF (2008) How primates (including us!) respond to inequity. (ed. D Houser & D McCabe) in Neuroeconomics: Advances in Health Economics series. Emerald, pp 99-124.

de Waal, FBM & Brosnan, SF (2006) Simple & complex social reciprocity in monkeys & apes. In Cooperation in Primates & Humans: Mechanisms & Evolution (ed. P Kappeler & C van Schaik). Springer Press.

**New Phil Trans issue on "Cooperation & Deception: From evolution to mechanisms" edited by Sarah Brosnan & Redouan Bshary

Sarah F. Brosnan, Ph. D.
Assistant Professor of Psychology & Neuroscience
Language Research Center
Georgia State University
PO Box 5010, Atlanta, GA 30302-5010 USA
email:; phone: 404-413-6301; fax: 404-413-6207
Lab webpage:
Personal webpage:

Courier address:
140 Decatur Street, Suite 1151, Atlanta, GA 30303-3083