Cooperation in animals has long been a major focus in evolutionary biology. In particular, reciprocal altruism, where helpful acts are contingent upon the likelihood of getting help in return, is especially intriguing because it is open to cheaters. In a new study published this week in the open-access journal PLoS Biology, Claudia Rutte and Michael Taborsky demonstrate the first evidence for generalized reciprocal cooperation in non-humans. The authors show that rats who received help in the past were more likely to help another unknown partner.
Although many models have predicted reciprocal altruism, scientists had found evidence only of direct reciprocity (“if you help me, I’ll help you”) in non-human animals in previous studies. Direct reciprocity is intuitively appealing, yet requires that animals interact repeatedly with the same individuals and remember past interactions. By comparison, generalized reciprocity makes no such cognitive assumptions. In generalized reciprocity, animals are more likely to help a partner if they have been helped in the past, regardless of the past helper's identity. For example, in humans, people who found a coin in the coin return of a telephone were more likely to help a stranger pick up dropped papers than control subjects who had not previously found money. In humans, this can be explained by cultural experience as well as by natural selection. But if similar reactions to anonymous experience can be found in non human animals, an evolutionary explanation would be far more likely.
In this study, Norway rats received help gaining food from a partner who pulled a stick to produce the food. Rats could therefore be grouped into two classes: those that had previously received help and those that had not. The rats who had previously been helped were then more likely to help another unknown partner receive food. This simple mechanism may promote the evolution of cooperation among unfamiliar non-relatives in many other animals.
Citation: Rutte C, Taborsky M (2007) Generalized reciprocity in rats. PLoS Biol 5(7): e196. doi:10.1371/journal.pbio.0050196.
University of Bern, Zoological Institute
PLEASE MENTION THE OPEN-ACCESS JOURNAL PLoS BIOLOGY (www.plosbiology.org) AS THE SOURCE FOR THESE ARTICLES AND PROVIDE A LINK TO THE FREELY-AVAILABLE TEXT. THANK YOU.
All works published in PLoS Biology are open access. Everything is immediately available—to read, download, redistribute, include in databases, and otherwise use—without cost to anyone, anywhere, subject only to the condition that the original authorship and source are properly attributed. Copyright is retained by the authors. The Public Library of Science uses the Creative Commons Attribution License.
AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.