Abstract # 131:

Scheduled for Friday, June 19, 2015 11:00 AM-11:15 AM: (Cascade F) Oral Presentation


J. Watzek1, M. Suchak2, S. M. Berman1 and F. de Waal1
1Living Links, Yerkes National Primate Research Center, Emory University, 2409 Taylor Ln, Lawrenceville, GA 30043, USA, 2Canisius College
     In any cooperative investment, there is a risk of leaving empty-handed. While cooperation in primates has attracted considerable research, little is known about the extent to which they assess outcomes before they invest. In this study, we examined whether chimpanzees are sensitive to changes in reward certainty. A captive group of 13 animals had simultaneous access to a cooperative task that required three individuals to pull a tray baited with food toward them. Potential rewards were clearly visible to the chimpanzees. Reward rates were manipulated across thirty 60-minute test sessions so that each location was baited independently, with a probability of either 0, .2, .4, .6, .8, or 1. Within a session, reward rates were the same for all three locations. Cooperation increased significantly, yet not proportionally with higher reward rates, indicating that success was not determined by reward contingencies alone, MANOVA Lambda=1.08, F(10,48)=5.58, p<.001, eta2=.54. Specifically, chimpanzees switched positions less frequently in sessions with certain outcomes (guaranteed gains or losses for all partners) than those with uncertain outcomes, ANOVA F(5,24)=6.07, p=.001, eta2=.56. These results underscore that chimpanzees flexibly respond to potential risks and benefits before they engage in cooperative efforts. By assessing outcomes prior to investing, chimpanzees ensure successful and efficient cooperation.