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ScientificAmerican.com <http://scientificamerican.com/>           

January 26, 2005
                
*Chimps' Sense of Justice Found Similar to Humans'*
                
Inequities big and small can lead people to believe that life is indeed 
not fair. But how humans respond to unfair situations depends on the 
social circumstances: inequality among friends and family, for instance, 
is less disturbing than it is among strangers. The results of a new 
study indicate that the same is true for chimpanzees, a finding that 
sheds light on how our sense of fairness evolved.

In the fall of 2003 Sarah Brosnan and Frans de Waal of the Yerkes 
National Primate Research Center in Atlanta determined that capuchin 
monkeys don't like being subjected to treatment they deem unjust. In the 
new work, the researchers tested the reactions of pairs of chimpanzees 
to exchanges of food that varied in quality. The animals received either 
a grape, which they coveted, or a less appealing cucumber, and they 
could see what their partner obtained. In pairs of chimps that had lived 
together since birth, the individual given the cucumber was less likely 
to react negatively to the situation than was the short-changed member 
of a pair that did not know each other as well. Indeed, chimps in the 
short-term social groups refused to work after their partner received a 
better reward for the same job. "Human decisions tend to be emotional 
and vary depending on the other people involved," Brosnan says. "Our 
findings 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."

Further experiments to investigate reactions to unfair situations are 
ongoing at the center in the hopes of understanding why we humans make 
the decisions we do. "Identifying a sense of fairness in two closely 
related nonhuman primate species implies it could have a long 
evolutionary history," Brosnan remarks. The findings will be published 
in the February 7 edition of the /Proceedings of The Royal Society B: 
Biological Sciences./ --/Sarah Graham/