Like Humans, Chimps Reward Cooperation and Punish Freeloaders

From Scientific American:

New research published today in Proceedings of the National Academy of Sciences suggests that despite being prone to occasional violent behavior, chimps actually much prefer cooperating over competing. In fact, the work shows that chimps work together at similar rates as humans—and that when violence does occur among apes, it is often directed toward an individual that is not being a team player.

Working with 11 chimps housed in a large outdoor enclosure at the Yerkes National Primate Research Center at Emory University, researchers devised an experiment to assess cooperation, defined as two or more chimps working together to access a food reward. Initially two chimps had to team up, with one lifting a barrier and the other pulling in a tray baited with small pieces of fruit. Once cooperation between two subjects was established, another barrier was added, requiring a third chimp to pitch in if all three were to obtain the spoils.

Given that the apes had nearly 100 hours to obtain their reward in the presence of bystander chimps, there were plenty of chances for competition to arise. The authors defined “competition” as episodes of physical aggression, bullying a fellow chimp to leave the scene of the reward or freeloading—stealing the prizes of others without putting in the work of retrieving them.

Although the study only looked at a small number of individuals, the results were telling. In 94 hour-long test sessions, the chimps cooperated with one another 3,565 times—five times more often than they were in competition. In addition, the animals used a variety of strategies to punish competitive behaviors, such as preferentially working with their more communal and tolerant fellow animals.

When aggression did occur, it was often used to subdue the overly competitive or prevent freeloading, perhaps an even greater affront to the chimpanzee honor code. …

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