New research suggests that what separates us from the apes may be our talent for trading: chimpanzees, it seems, just don't have it in them.

Economists believe that barter—whereby an individual must give up something valuable in exchange for another valuable commodity—lies at the root of human economic development. In an effort to provide more insight into this phenomenon, a group of researchers led by Sarah Brosnan of Georgia State University (Atlanta) and Mark F. Grady of the University of California, Los Angeles investigated the circumstances under which chimpanzees might engage in similar behavior.

The researchers tested two groups of chimpanzees, one that had undergone extensive cognitive training and one that hadn't (PLoS ONE 1, e1518; 2008). Though initially slow to catch on, chimpanzees were trained to exchange one type of food for another. The scientists found that when chimpanzees were given the option of receiving a highly desirable food (grapes) in exchange for an undesirable food (carrot pieces), they were almost always willing to trade. When foods were closer in value, however, such as apple slices and grapes, chimpanzees were far less likely to trade than would be expected based on prior assessment of their preferences. Both groups of chimpanzees performed similarly, though results varied between individuals.

One possible explanation for chimpanzees' reluctance to trade is the risk that an exchange partner might run away with both commodities. When the potential loss is high in relation to the potential gain, a chimpanzee might be less likely to take a chance. The reliability of the exchange partner is also crucial. “In every case, the experimenter was an individual with whom the chimpanzees had worked for a decade or more,” Brosnan tells Lab Animal. “I think that they would have been even less likely to barter with an unfamiliar human experimenter, or one whom they disliked.”

An additional factor may be that chimpanzees cannot conceive of 'owning' an item unless it is in their possession at a given moment. This means that they do not naturally hoard large quantities of items and would therefore be less likely to develop their capacity for barter. Chimpanzees do, however, exchange services such as grooming and support.

According to Brosnan, the group is currently using chimpanzees trained in symbol language to investigate whether the apes will barter with each other, a situation that may more closely reflect their natural tendencies.