Humans excel at following conventions. In France, acquaintances greet one another with a kiss on the cheek. In Japan, they bow. The different greetings have no inherent use on their own--and they would each lose their meaning when performed in the wrong context. But are humans the only animals to use such social conventions? A new study in chimps suggests not; the primates can learn an arbitrary behavior and pass it along to their groupmates.
The behaviour in question involved objects that chimps would normally deem useless. Graduate student Kristin Bonnie of the Yerkes National Primate Research Center in Atlanta, Georgia, and her colleagues provided two groups of chimpanzees with either a bucket with a hole cut in the side or a container with a large tube sticking out of the top. Out of sight of the other group members, the researchers trained one high-ranking female from each group to deposit tokens into either the bucket or the tube. The team then sat back and watched to see if that trained behavior would spread.
Indeed, the other animals quickly realized that the trained group member was receiving treats--apple or banana slices--for picking up the tokens and placing them in a container. Although treats were available for chimps that used either receptacle, each group followed their leader and used just one of the two options. There was only one exception: A low-ranking female in one group figured out she could get rewards for using the second container, but none of her group members followed her lead.
Bonnie and her colleagues say the results, reported online this week in the Proceedings of the Royal Society B, suggest that the evolutionary roots of humans' tendency to follow convention are also present in our chimpanzee cousins. While other studies have shown that different chimp groups use similar tools in different ways (ScienceNOW, 22 August 2005), this is the first controlled study that shows chimps can follow conventions that don't involve tools, Bonnie says.
The experiment is "getting closer to the heart of cultural phenomena where you're only doing something because it's the local way of doing it," says study co-author Andrew Whiten of the University of St. Andrews in Fife, United Kingdom. But psychologist Michael Tomasello of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, says the experiment doesn't cleanly demonstrate that chimps can pick up a completely arbitrary custom. Learning that performing a certain action results in a reward is not the same as doing something just because everyone else is doing it, he says.