Chimpanzees duplicate modeled sequences of arbitrary actions by socially observing group members, demonstrating the consistency necessary to create and sustain different local traditions, according to a new study conducted at the Yerkes National Primate Research Center, Emory University. This study disproves previous research that suggested nonhuman species lacked the capacity to observationally learn the significance of arbitrary actions, a characteristic considered fundamental to human culture.
Based on a new experimental design featuring two arbitrary sequences of actions, both having no logical connection to reward and lacking significance prior to the experiment, this study showed chimpanzees extracted both the form and benefits of these sequences through social observation. The new design, in contrast to ones used in previous studies that explored how chimpanzees learn the significance of novel arbitrary behaviors, relied on same-species interaction rather than cross-species interaction.
Published in the current issue of the Proceedings of the Royal Society of London by Yerkes researchers Kristin E. Bonnie, Victoria Horner, PhD, and Frans B. M. de Waal, PhD, director of the Yerkes Living Links Center, and University of St. Andrews researcher Andrew Whiten, PhD, this study shows unprecedented consistency in experimentally seeded alternative traditions in nonhuman primates and lends support to the idea certain object-directed behaviors are socially learned in wild chimpanzees.
The study relied on two chimpanzee groups, each introduced to one of two rewarded, alternative sequences to a complex sequence of behaviors. The alternative sequences included collecting, transporting and depositing a plastic token into a bucket or a pipe to receive a food reward from a separate, unrelated location. When each group of chimpanzees observed a high-ranking female model from its own group complete an action sequence, the majority of the animals followed that sequence for the remainder of the testing period.
"The action sequences in this study are defined only by the individuals within the group to create arbitrary practices," said de Waal. "In each community, members know the local meaning of an object, reacting to it in a unique but predictable manner, similar to behaviors seen in human social groups and among wild chimpanzees. By understanding how arbitrary practices originate in chimpanzees, we may gain better understanding of human practices and the way human culture and behavior has evolved."
Because both groups of chimpanzees had the opportunity to discover either sequence of token behaviors individually and to receive a reward for any successful method, researchers found that the observed behavioral differences only could be attributed to ape-to-ape transmission. "Our data show the chimpanzees were unlikely to develop different behavior through individual experience," said Bonnie. "Any learned behavior most likely was due to the chimpanzees' recognition of the perceived significance of the action sequence performed by the high-ranking female model in each group."
Further research by the Living Links Center, established in 1997 at the Yerkes Research Center for primate studies that shed light on human behavioral evolution, may expand on these findings by examining social factors supporting or inhibiting acquisition of traditions within social groups.
For more than seven decades, the Yerkes National Primate Research Center of Emory University has been dedicated to advancing scientific understanding of primate biology, behavior, veterinary care and conservation, and to improving human health and well-being. Today, the center, as one of only eight National Institutes of Health–funded national primate research centers, provides specialized scientific resources, expertise and training opportunities.
Recognized as a multidisciplinary research institute, the Yerkes Research Center is making landmark disco veries in the fields of microbiology and immunology, neuroscience, psychobiology and sensory-motor systems. Research programs are seeking ways to: develop vaccines for AIDS and malaria; treat cocaine addiction; interpret brain activity through imaging; increase understanding of progressive illnesses such as Parkinson's and Alzheimer's; unlock the secrets of memory; determine behavioral effects of hormone replacement therapy; address vision disorders; and advance knowledge about the evolutionary links between biology and behavior.