Ph.D., Emory University, 2004 Assistant Professor Member, Social/Cognitive Program Member, NBN Program sbrosnan@gsu.edu 404-413-6301 710 Urban Life 404-241-8164 Language Research Center My personal/lab webpage

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.

Representative Publications

Brosnan, Sarah F. (in press)  Inequity and Prosocial behavior in chimpanzees.  (ed. Elizabeth Lonsdorf, Steven Ross, and Tetsuro Matsuzawa) in The Chimpanzee Mind.  University of Chicago Press.

Vonk, Jennifer, Brosnan, Sarah, Silk, Joan B., Henrich, Joseph, Schapiro, Steven, Richardson, Amanda, Lambeth, Susan P., Povinelli, Daniel J. (submitted)  Chimpanzees do not take advantage of very low cost opportunities to deliver food to unrelated group members.  Animal Behaviour.

Van Wolkenten, Megan, Brosnan, Sarah F., and de Waal, Frans B. M. (submitted)  Inequity responses of monkeys modified by effort.  PNAS.

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

Brosnan, Sarah F. (2006)  At a crossroads of disciplines.  Journal of Social Justice 19: 218-227.

Brosnan, Sarah F., Freeman, Cassie, and de Waal, Frans B. M. (2006)  Equitable behavior, not reward distributions, affect capuchin monkey’s (Cebus apella) reactions in a cooperative task.  American Journal of Primatology 68: 713-724.

de Waal, Frans B. M. and Brosnan, Sarah F.  (2006)  Simple and complex social reciprocity in monkeys and apes.  In Cooperation in Primates and Humans: Mechanisms and Evolution  (ed. Peter Kappeler & Carel van Schaik).  Springer Press.

Brosnan, Sarah F. and de Waal, Frans B. M.  (2006)  Partial support for a non-replication: Commentary on Roma, Silberberg, Ruggiero, and Suomi (2006).  Journal of Comparative Psychology 120(1): 74-75.

Silk, Joan B., Brosnan, Sarah F., Vonk, Jennifer, Henrich, Joseph, Povinelli, Daniel, Richardson, Lambeth, Susan, Amanda, Mascaro, Jenny, and Schapiro, Steven.  (2006)   Animal Behavior: Chimpanzee choice and prosociality (Reply).  Nature 440: E6.

Brosnan, Sarah F.  (2006) An exploration of culture: Review of “The Cultured Chimpanzee:  Reflections on cultural primatology” by William McGrew.  American Journal of Primatology 68: 425-427.

Silk, Joan B., Brosnan, Sarah F., Vonk, Jennifer, Henrich, Joseph, Povinelli, Daniel, Richardson, Lambeth, Susan, Amanda, Mascaro, Jenny, and Schapiro, Steven.  (2005)   Chimpanzees are indifferent to the welfare of unrelated group members.  Nature 437: 1357-1359.

Brosnan, Sarah F. and de Waal, Frans B. M. (2005) A simple response to barter in chimpanzees (Pan troglodytes).  Primates 46: 173-182.

Brosnan, Sarah F., Schiff, Hillary C., and de Waal, Frans B. M. (2005)  Chimpanzees’ (Pan troglodytes) reactions to inequity during experimental exchange.  Proceedings of the Royal Society of London<, Series B 1560: 253-258.

Brosnan, Sarah F. and de Waal, F.B.M. (2005) A cross-species perspective on
 the selfishness axiom: Commentary on Henrich et. al.  Behavioral and Brain Sciences 28: 818.

Brosnan, Sarah F. and de Waal, Frans B. M. (2004) Reply to "Inequity aversion in capuchins". Nature 428: 140.

Brosnan, Sarah F. and de Waal, Frans B. M. (2004)  A concept of value during experimental exchange in brown capuchin monkeys.  Folia Primatologica 75: 317-330.

Brosnan, Sarah F. and de Waal, Frans B. M. (2004) Socially learned preferences for differentially rewarded tokens in the brown capuchin monkeys (Cebus apella).  Journal of Comparative Psychology 118 (2): 133-139.

Brosnan, Sarah F. and de Waal, Frans B. M. (2003) Monkeys reject unequal pay. Nature 425: 297-299.

Brosnan, Sarah F., Dugatkin, Lee A., and Early, Ryan L. (2003) Observational learning and predator inspection in guppies, (Poecilia reticulata). Ethology 109: 823-834.

Brosnan, Sarah F. and de Waal, Frans B. M. (2003) Regulation of vocalizations by chimpanzees finding food in the presence or absence of an audience. Evolution of Communication 4 (2): 211-224.

Brosnan, Sarah F. and de Waal, Frans B. M. (2002). Variations on tit-for-tat: Proximate mechanisms of cooperation and reciprocity. Human Nature 13 (1): 129-152.