Researchers at the Yerkes National Primate Research Center, Emory University, have shown capuchin monkeys, just like humans, find giving to be a satisfying experience. This finding comes on the coattails of a recent imaging study in humans that documented activity in reward centers of the brain after humans gave to charity. Empathy in seeing the pleasure of another's fortune is thought to be the impetus for sharing, a trait this study shows transcends primate species.
The study is available online in the Early Edition of the Proceedings of the National Academy of Sciences.
Frans de Waal, PhD, director of the Living Links Center at the Yerkes Research Center, and Kristi Leimgruber, research specialist, led a team of researchers who exchanged tokens for food with eight adult female capuchins. Each capuchin was paired with a relative, an unrelated familiar female from her own social group or a stranger (a female from a different group). The capuchins then were given the choice of two tokens: the selfish option, which rewarded that capuchin alone with an apple slice; or the prosocial option, which rewarded both capuchins with an apple slice. The monkeys predominantly selected the prosocial token when paired with a relative or familiar individual but not when paired with a stranger.
"The fact the capuchins predominantly selected the prosocial option must mean seeing another monkey receive food is satisfying or rewarding for them," said de Waal. "We believe prosocial behavior is empathy based. Empathy increases in both humans and animals with social closeness, and in our study, closer partners made more prosocial choices. They seem to care for the welfare of those they know," continued de Waal.
de Waal and his research team next will attempt to determine whether giving is self-rewarding to capuchins because they can eat together or if the monkeys simply like to see the other monkey enjoying food.
The research was supported by a grant from the National Science Foundation and by the Yerkes base grant from the National Institutes of Health. Reference: "Giving is self-rewarding for monkeys." Frans B. M. de Waal; Kristin Leimgruber; Amanda R. Greenberg, Proceedings of the National Academy of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.0807060105.
For more than seven decades, the Yerkes National Primate Research Center, Emory University, has been dedicated to conducting essential basic science and translational research to advance scientific understanding and to improve the health and well-being of humans and nonhuman primates. Today, the center, as one of only eight National Institutes of Health--funded national primate research centers, provides leadership, training and resources to foster scientific creativity, collaboration and discoveries. Yerkes-based research is grounded in scientific integrity, expert knowledge, respect for colleagues, an open exchange of ideas and compassionate, quality animal care.
Within the fields of microbiology and immunology, neuroscience, psychobiology and sensory-motor systems, the center's research programs are seeking ways to: develop vaccines for infectious and noninfectious diseases, such as AIDS and Alzheimer's disease; 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.
The goal of the Living Links Center at the Yerkes National Primate Research Center is to view great apes as a window to the human past by studying their behavior, cognition, neuroanatomy, genes and reproduction in a noninvasive manor. Another goal is to educate the public about apes and to help guarantee their continued existence in the wild.