Abstract # 134:

Scheduled for Friday, June 19, 2015 11:15 AM-11:30 AM: (Cascade F) Oral Presentation


M. W. Campbell1,2,3, M. Suchak2,3,4,5, J. Watzek2,3,6 and F. B. de Waal2,3,5
1California State University - Channel Islands, One University Dr., Madera Hall, Camarillo, CA 93012, USA, 2Living Links Center, 3Yerkes National Primate Research Center, 4Canisius College, 5Emory University, 6Georgia State University

Cooperative events in the wild involve many variables that have not typically been tested when studying cooperation in captivity. We recently used free access to a device requiring 3 individuals to work at the same time to better model the richness of chimpanzee cooperative interactions in the wild. But, all 3 chimpanzees received the same reward, and in the wild resources are not always divided evenly. To incorporate unequal outcomes, we placed 3 grapes at two of the locations and 1 grape at the other location. When the apparatus was unoccupied, chimpanzees preferred to approach the locations with 3 rewards, which demonstrated understanding of the reward differences and motivation for the higher amount. The chimpanzees succeeded at the task almost 700 times in 20 1-hour sessions, showing tolerance for unequal outcomes. Looking at the mechanisms for this tolerance, access to the high value locations seemed to be determined by rank, which may have limited aggression. Low rank may have allowed acceptance of the lesser amount (a grape is still a preferred item) and relative distribution. For chimpanzees, rank may enable cooperation when rewards are moderately unevenly distributed. It remains to be seen how extreme inequity and effort may influence rates of cooperation.