Faced with two choices, each equally rewarded, the capuchins placed tokens in both striped and polka-dotted buckets. But when the dominant male favored only one type of bucket, other capuchins followed.
This exercise was part of a study exploring the influence of social context on behaviors in capuchin monkeys at Franklin & Marshall College. The journal “Behaviour” recently published an article on the research, “Seeding an arbitrary convention in capuchin monkeys: the effect of social context,” by F&M Assistant Professor of Psychology Elizabeth Lonsdorf and, at the time, four student co-authors: Michelle Grim ’14, Alexander Krupnick ’14, Madison Prestipino ’15, and Julia Whyte ’15.
Lonsdorf and her research team studied two groups of capuchin monkeys that are maintained by F&M – the Fummers and the Yalies. Each group lives and socializes independently, each with its own social orders and dynamics.
“Capuchins are one of the smartest of the small primates, and show many complex social and cognitive behaviors that are similar to species more closely related to humans, like chimpanzees,” Lonsdorf said.
The study explores the influence of social context on behaviors in capuchins, who are known to be skilled social learners. They are able to learn foraging and other survival techniques from their peers. The researchers investigated whether capuchins would adopt an arbitrary convention that is demonstrated by a leader in their group.
They selected the arbitrary convention of placing a token into one of two patterned buckets. All of the capuchins were rewarded with food equally for completing the task using either receptacle. However, the alpha male of each colony was trained to select only one of the buckets. Among both groups, the capuchins readily followed the arbitrary convention demonstrated by their leader.
Results show that capuchins can adopt an arbitrary convention through social learning. As individuals, the monkeys preferred arbitrary convention even when given an equally rewarded alternative. However, researchers observed that in a group setting, the higher-ranking monkeys were more likely to complete the task than the lower-ranking. The finding shows how influential rank are in determining behaviors.
Lonsdorf said the research would not be possible without the resources and standards of care provided at the College. Any engagement with the capuchin monkeys is non-invasive and on a voluntary basis, which means the monkeys choose whether to participate.
To work directly with animals, students must first demonstrate responsibility, compassion and commitment as volunteers. They can begin their lab training as members of the husbandry or enrichment teams under the supervision and mentorship of the director of animal operations, Lillian Basom. Each semester, 30-45 students train on one of these teams.
On the husbandry team, students focus on positive reinforcement training with the capuchins, like teaching them to sit on a scale to monitor healthy weights or to shift from one area of the enclosure to another on command. On the enrichment team, students provide the animals with objects or activities that promote natural behaviors specific to the species and then collect data on how the animals engage with the enrichment device.
Students who gain experience on the husbandry or enrichment teams can apply for a research position. Senior Cassandra Festa, animal behavior major and now a research team leader, began volunteering on the husbandry team as a first year student. Her experience inspired her to work with primates in sanctuaries abroad, where she intends to continue after graduating in the spring.
“I've returned to Costa Rica every summer and found a passion I never knew existed – one strongly focused on monkeys in general, monkey welfare, and monkey care,” Festa said.
Lonsdorf came to F&M in 2012 and became head of the primate research laboratory. A longtime researcher at Gombe Stream Research Centre in Africa, Lonsdorf continues to conduct field work with chimpanzees in Tanzania in collaboration with the Jane Goodall Institute.
“Capuchins and chimpanzees have remarkably similar social behaviors and cognitive skills even though they are quite distantly related on the primate evolutionary tree,” Lonsdorf says. “The research we do at F&M contributes to the discoveries about primates around the world as well as training the next generation of animal researchers.”