Study Finds Chimps, Bonobos Practice Reciprocal Gifting

Alan McStravick for – Your Universe Online

If your mother was anything like mine, you learned early on that it is better to give than to receive. There is something seemingly inherent in our biology that gives us a certain amount of joy when bestowing gifts and favors upon those we love and care for. But what about more casual relationships, such as with the neighbor or co-worker? Do we offer favors and gifts to them out of mere philanthropy or are we expecting a quid pro quo recompense? New research offered out of the University of California, Santa Barbara (UCSB) might shed a little light on this quirk of gift giving.

The team, lead by Adrian Jaeggi, a postdoctoral researcher in anthropology at UCSB, and a junior research fellow at the school’s SAGE Center for the Study of the Mind, has decided to explore this question of inter-relational reciprocity by examining the behaviors of chimpanzees and bonobos. Their results have been published in the current online issue of the journal Evolution & Human Behavior.

“The article focuses on the question of whether individuals do favors because they expect them to be reciprocated at some other time, and, more specifically, whether such exchanges have to happen immediately, or can take place over longer time spans,” Jaeggi explained. “We studied the question in chimpanzees and bonobos —— our two closest living relatives —— and looked at the exchanges of grooming and food sharing, which are two common types of favors among these apes.”

What Jaeggi and his team learned was interesting, on two fronts. Some of the results showed there was evidence of quid pro quo immediate exchanges between the primates. However, the stronger evidence discovered supported the idea that exchanges were made with an eye on the long term. The researchers found that calculated exchanges, ones made where a detailed score of past exchanges is kept, happen far less frequently in stable relationships.

“In the chimp group we studied, we knew there was a lot of this long-term exchange,”  Jaeggi said in a prepared statement. “We didn’t find any evidence for a short-term effect.”

Chimpanzees live in stable social groups, he continued, and have a relatively long life span. They recognize others in the group, form long-term relationships, and associate with individuals who have helped them in the past.

“In the wild, for example, chimps hunt for smaller monkeys, and they commonly share the meat. It’s similar to what hunters and gatherers do,” Jaeggi said. “Our experiment is meant to mimic the situation in which you have a large monopolized food item.”

Using grooming as the favor, the researchers studied whether or not a chimp that had just been groomed was more likely to share food with the pal who had groomed him. “That would provide evidence for keeping track of who has done a favor,” Jaeggi said. However, grooming releases endorphins, he added, and that general sense of wellbeing on the part of the food owner might lead to more indiscriminate food sharing.

“We found that sharing was predicted by who the chimps’ long-term friends and partners were,” he said. “Grooming just before didn’t play a role. Food owners didn’t share specifically with their groomers. Nor did the groomers act in return. They didn’t pay for the food, and they didn’t reward the food owner’s generosity afterward.”

On the other side of the hierarchical structure, however, live the bonobos. Where chimpanzees have established a dominance hierarchy, bonobos have no such social structure. This means that at any given time, bonobos are unable to recognize where they might fit within the group. Bonobos also don´t form coalitions like the chimpanzees.

“The food sharing situation sort of freaked them out,” said Jaeggi. “All of a sudden there´s all this food that´s owned by one individual, and they don´t really know what to do about it. They want to get it, but they don´t dare, because they don´t know what the consequence will be.”

Also of note from the study was how the bonobos engaged in the act of grooming more frequently. According to Jaeggi, this is most likely because they sought the calming effects of the endorphins. “And there we did see an effect of grooming on sharing,” he said. “Chimps would go and take food pretty confidently, but Bonobos were more reticent. They´d reach out and then groom. It seemed to be that they´d groom to release tension, and then there would be these short-term reciprocal exchanges.”

The researchers pointed out they believe, however, these short exchanges were more of a byproduct of the need to reduce tension rather than short-term contingencies that were used to establish a relational reciprocity.

“It´s really not qualitatively different from what people do,” Jaeggi commented. “They establish these lasting relationships, and within them, services are exchanged without the participants keeping close track of who´s doing what for whom.”

But if you´ve ever been in a less stable or casual relationship, you´ll probably recognize that we humans have the ability to keep tabs on what we give compared to what we receive. That scorecard style of reciprocity raises questions for Jaeggi and his team, regarding its purpose and how it came to be developed. “Maybe that´s something that´s more culturally learned.”

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