Researchers review a series of studies and report that nonhuman primates vary their vocalizations depending on their relationship with the listener and social context. Compared with humans, nonhuman primates display small vocal repertoires that undergo little modification during development. Researchers have previously suggested that vocalizations may not serve as a measure of social bond strength due to the limited acoustic range of nonhuman primates. Dorothy L. Cheney and Robert Seyfarth reviewed studies of nonhuman primate vocalizations in various contexts, and found that the presence of other individuals, whether kin or rivals, influenced the production of calls. Baboons, for example, have been found to use grunting to signal friendly intent. Primates have also been observed to use modifications of vocalizations to convey messages. Bonobos, which function in a complex social system, add a whistle to their usual hooting call when desiring to leave one group and join another. The authors note that the modification of vocalization likely serves to reduce uncertainty in communication, and appears to be tied to the relationship between the caller and the listener. Studies of nonhuman primates' neural activity during social interaction suggest that, similar to humans, activity in the brain's anterior cingulate cortex may mediate social decisions. Although nonhuman primates appear to be incapable of vocal imitation or learning entirely new calls, their flexible usage of vocalization may constitute an important link between nonlinguistic communication and development of language, according to the authors.
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Article #17-17572: "Flexible usage and social function in primate vocalizations," by Dorothy L. Cheney and Robert Seyfarth.
MEDIA CONTACT: Dorothy L. Cheney, University of Pennsylvania, Philadelphia, PA; tel: 215-898-6915; e-mail: < cheney@sas.upenn.edu >
Proceedings of the National Academy of Sciences