Cultural norms not unique to human societies

Yerkes-based experiment confirms cultural transmission and conformity in chimpanzee communities

Humans are not alone in their desire to conform to cultural norms, according to new study findings that confirm, for the first time, chimpanzees share the same conformist tendencies. Researchers, in determining how chimpanzee communities share and maintain traditions, discovered they possess a natural motivation to copy their peers well into adulthood and say that although other species show some cultural behaviors, the level of cultural variation shown by chimpanzees is exceeded only by humans. The study, conducted at the Yerkes National Primate Research Center of Emory University by a collaborative team of scientists from the United States and the United Kingdom, is published in the current online edition of Nature.

Unlike previous studies that used human models for cultural-learning experiments with chimpanzees, researchers Victoria Horner, PhD, and Frans B. M. de Waal, PhD, of the Living Links Center at the Yerkes Research Center, and Andrew Whiten, PhD, of the University of St. Andrews, Scotland, applied a unique method that extends the experimental approach to the group

level, focuses on ape-to-ape transmission and uses a two-action methodology. This approach bridges the gap between two conventional research methods: population-level observations on wild apes and one-to-one social learning experiments.

In the study, researchers introduced a naturalistic foraging task into three groups (two experimental and one control) to see if chimpanzees can learn by observation. While unseen by other chimpanzees, researchers taught a high-ranking female from each of the two experimental groups a different way, either Lift or Poke, to retrieve food from a system of tubes called Pan-pipes. Once the two females mastered the task, other chimpanzees within their groups were allowed to watch them perform the new skill over a seven-day period before all group members were allowed to use the tool. According to the researchers, group members gathered around the local expert, watched attentively and proved successful when allowed to try the task on their own. The third group, which did not have the benefit of a local expert and was left to decipher the task on its own, was unsuccessful in retrieving food from the Pan-pipes.

“This study demonstrates apes do copy members of their own species and they develop different traditions by doing so,” said Dr. Horner. “It makes it likely differences in tool use between wild chimpanzee communities in Africa indeed reflect a form of culture and establishes another link between human and chimpanzee societies.”

The conformity bias finding was an unexpected, but equally important, result of this culture study, according to Dr. Horner. A few members of each group independently discovered the alternative method for freeing food from the Pan-pipes, but this knowledge did not endanger the groups’ traditions because most of these chimpanzees reverted back to the norm set by their local expert. “Choosing the group norm over the alternative method shows a level of conformity we usually associate only with our own species,” said Dr. Horner. “By using the group’s technique rather than the alternative method, we see the conformity is based more on a social bond with other group members than the simple reward of freeing the food.”

A characteristic traditionally thought to be solely human, the propensity to conform, may be part of an evolutionary progression. “These results suggest an ancient origin for the cultural conformism that is so evident in humans,” said de Waal. “Further research may reveal these findings to be more widespread throughout the animal kingdom.”