Sarah F. Brosnan
Georgia State University, Departments of Psychology, Philosophy & Neuroscience
Keeling Center for Comparative Medicine & Research, MD Anderson Cancer Center
The human sense of fairness is an evolutionary puzzle; why do we put so much value on what we receive relative to others? One answer to this question emerges from studying other species. Although fairness itself is hard to study, it can be translated empirically into how individuals respond to different reward distributions and studying other species’ reactions can tell us something about the evolution of our own behavior. Indeed, humans are not alone in disliking inequity; many species protest receiving less than a partner for the same task, and this tendency occurs primarily in species that cooperate, indicating a link between the two behaviors. I hypothesize that this response acts as a partner choice mechanism that allows individuals to recognize good cooperative partners. However, a full sense of fairness requires not only this, but also that individuals notice and seek to equalize outcomes to their own detriment. There is less evidence of this latter reaction in nonhuman species, although it has been documented in our closest relatives, the apes. If the inequity response functions as a partner choice mechanism, this reaction likely reflects an attempt to forestall one’s partner’s dissatisfaction and its negative impact on future cooperation. Therefore, it is likely that the evolution of this response, combined with advanced abilities at inhibition and planning, allowed the development of a full sense of fairness in humans, which allows for the extensive cooperation we see in our own species.
Sarah Brosnan is a Distinguished University Professor of Psychology, Philosophy and Neuroscience and Co-Director of the Language Research Center at Georgia State University. She studies decision-making in humans and other primates, particularly decisions relating to cooperation and inequality, and how those decision processes evolved. She is a Fellow of the APA and SESP, and an Editor of Proceedings of the Royal Society, Series B. She has published in top journals, including Nature, Science, and PNAS and is funded by NSF and several foundations. Her book, “Cooperation and Conflict: The interaction of opposites in shaping social behavior,” co-edited with Walt Wilczynski, was published by Cambridge University Press in 2021. You can learn more about her research at http://www.sarah-brosnan.com