London, July 1 (ANI): A French researcher has found that grooming acts as a common currency among monkeys, and that the non-human primates exchange it for food, greater tolerance from dominant members of the group, and sex.

Ronald Noe, associated with the University of Strasbourg, created an artificial market in groups of vervet monkeys by introducing a plastic box filled with food that only one subordinate female was trained to open. The aim was to see how the exchange system works.

The researcher says that just an hour after the female opened the box, it was observed that she was rewarded by being groomed more often and for longer by other group members, and that she could afford to groom dominant group members less often.

Noe and colleagues later halved the importance of the female's ability to provide food, by introducing a second lunch box that only a second female could open.

The first female's grooming "stock value" decreased, while the second monkey's rose, until both arrived at roughly the same value and were groomed for the same amount of time.

"One can say that the second provider was groomed at a cost of the first provider," New Scientist magazine quoted Noe as saying.

A research article describing the study has been published in the journal Proceedings of the National Academy of Sciences. (ANI)