Chimps don't just get mad, they get even

Humans are the most cooperative species on the planet, and the most punitive. This is no coincidence. When I promise to take a friend to the airport to catch an early-morning flight, I have to overcome the temptation to sleep an extra couple of hours. My motivation to follow through on my promise is influenced by my awareness of the consequences: my friend will miss her plane, and I will feel guilty. My friend will probably be angry with me, and she may refuse to help me the next time I ask. Worse yet, she may tell other people what I did, and they may share her outrage and anger. The threat of these kinds of sanctions helps to sustain cooperation within dyads and larger groups (1–4). There is now considerable interest in the evolution of cooperation and punishment in human societies, and there have been a number of efforts to explore the phylogenetic origins of cooperative motives in other primates (4–8). Virtually all of the work on other primates has focused on the willingness to provide benefits to conspecifics. In this issue, Jensen et al. (9) turn the tables and examine chimpanzees' propensity to impose sanctions on familiar group members who commit transgressions.

To study chimpanzees' propensity for punitive behavior, Jensen et al. (9) devised an ingenious experimental protocol in which one chimpanzee was given the opportunity to respond to the loss or inaccessibility of valued food items by pulling a rope that caused a platform to collapse and the food to fall out of reach. This setup allowed the researchers to examine how chimpanzees responded when food was inaccessible or taken away from them, how they responded to disparities in outcomes between themselves and others, and their sensitivity to the role others played in …

*E-mail: jsilk{at}anthro.ucla.edu