By observing variability in chimpanzees' responses to inequity, Sarah Brosnan, PhD, and Frans de Waal, PhD, both researchers in Yerkes' Division of Psychobiology and the Yerkes-based Living Links Center, determined the chimpanzees' responses depended upon the strength of their social connections. This is the first demonstration that nonhuman primates' reactions to inequity parallel the variation in human responses to unfair situations based on the quality of the relationship. This novel finding appears January 26 on the Proceedings of the Royal Academy of Sciences, Series B web site, www.journals.royalsoc.ac.uk. The finding also will appear in the journal's February 7 print edition.

Coupled with data from the authors' previous fairness-related research in capuchin monkeys, released in fall 2003, Brosnan and de Waal's current research provides new insight into the role social environment and relationships play in human decision-making. In their previous study, the researchers identified for the first time a sense of fairness in nonhuman primates and correlated that finding to human economic decision-making.

"Human decisions tend to be emotional and vary depending on the other people involved," said Brosnan. "Our finding in chimpanzees implies this variability in response is adaptive and emphasizes there is not one best response for any given situation but rather it depends on the social environment at the time."

In the current study, Drs. Brosnan and de Waal made food-related exchanges with chimpanzees from groups that had lived together either their entire lives or a relatively short time (less than eight years). Animals were paired to determine how they would react when their partners received a superior reward (grapes) instead of a less-valued reward
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Contact: Kelly Thompson
kthomp8@emory.edu
404-727-9254
Emory University Health Sciences Center
25-Jan-2005