Thursday, January 1, 2009

Biology Letters: Calculated reciprocity after all: computation behind token transfers in orangutans


From the BBC item http://news.bbc.co.uk/2/hi/science/nature/7797776.stm:
"So we have a calculation behind the giving," explained Valerie Dufour who led the research at the Scottish university. "If you don't give me enough, then I don't give you either; but if you give me enough, OK, then I buy your co-operation, and I secure it by giving too."
Many animals exchange goods and services with each other; the grooming of primates is an obvious example. But the researchers say there has been no experimental evidence before of "calculated reciprocity", where animals adapt their own behaviour in response to how another is helping them. "It's not just humans that calculate about giving, and it's not just humans who expect to be given something in return when they are co-operative," Dr Dufour told BBC News. "Orangutans do that too."
However, other apes - chimpanzees, gorillas and bonobos - were less able or willing to play the game.


V. Dufour, M. Pelé, M. Neumann, B. Thierry, J. Call. 2008. Calculated reciprocity after all: computation behind token transfers in orangutans. Biology Letters (Royal Society).
http://journals.royalsociety.org/content/qv2203362277hn50/

Authors abstract:
Transfers and services are frequent in the animal kingdom. However, there is no clear evidence in animals that such transactions are based on weighing costs and benefits when giving or returning favours and keeping track of them over time (i.e. calculated reciprocity). We tested two orangutans (Pongo pygmaeus abelii) in a token-exchange paradigm, in which each individual could exchange a token for food with the experimenter but only after first obtaining the token from the other orangutan. Each orangutan possessed tokens valuable to their partner but useless to themselves. Both orangutans actively transferred numerous tokens (mostly partner-valuable) to their partner. One of the orangutans routinely used gestures to request tokens while the other complied with such requests. Although initially the transfers were biased in one direction, they became more balanced towards the end of the study. Indeed, data on the last three series produced evidence of reciprocity both between and within trials. We observed an increase in the number and complexity of exchanges and alternations. This study is the first experimental demonstration of the occurrence of direct transfers of goods based on calculated reciprocity in non-human-primates.